Astronomy Final

Galaxy clusters...

Contain dark matter Can have huge giant elliptical galaxies at their centers Are surrounded by empty volumes called "voids" More than one of the above are correct

Why does fusion stop in white dwarfs?

Degeneracy keeps the atoms apart and does not allow them to get close enough to fuse even though the temperature and pressure is large enough.

) filament:

A prominence seen against the disk of the sun

seeing

A quantity measuring the stability of Earth's atmosphere.

resonance

A repeated, periodic push or pull capable of summing into a larger push or pull

evolutionary track

A representation of the changes in color and luminosity of an evolving star.

meteorite

A rock or iron specimen that has fallen from space

globular cluster

A round, massive cluster of stars.

meteoriod

A small (less than a few hundred meters across) chunk of rock in space

emission spectrum

A spectrum of light with energy at only a few wavelengths.

Oort cloud

A spherical shell of comets that orbit the sun at a great distance (roughly two light years from the sun).

pulsar

A spinning neutron star.

continuous spectrum

A spread of light with an uninterrupted wavelength distribution of energy.

main sequence star

A star fusing hydrogen to helium in its core

supernova

A star that blows itself apart.

nova

A star that erratically and explosively brightens and dims.

asymptotic giant branch star

A star that has become a red giant for a second time. It is burning helium to carbon in a shell surrounding the core.

red giant star

A star that is burning hydrogen to helium in a shell surrounding its core

protostar

A star that is in the process of forming. It glows from gravitational contraction

white dwarf

A star that is very small and hot. The end state of a low mass star.

brown dwarf

A star without enough mass to begin hydrogen fusion.

meteor

A streak of light in the atmosphere

electron

A subatomic particle with a negative charge. It creates light.

Describe what a sunspot is:

A sunspot is a region in the photosphere where the sun's magnetic field erupts through the surface. It is cooler than the surrounding area and looks dark by comparison.

active optics

A technique using computer-controlled mirrors to sharpen images distorted by the atmosphere

terrestrial planet

A term referring to Earthlike planets

Jovian planets definition

A term referring to Jupiter-like planets.

differential rotation

A term referring to the orbital character of stars near the sun

Describe what a theory is and how it differs from an hypothesis.

A theory is a tested and refined explanation while an hypothesis is an educated guess that does not have the depth and breadth of a theory. Hypotheses are tentative while theories have stood up to more careful scrutiny.

accretion disk

A toroidal or donut-shaped collection of material attracted to a central body like a star or black hole

Time/ temperature: 0/infinite

Big Bang

When the jet of an AGN points at us we see a

Blazar

Which of these is a prominence seen against the disk of the Sun?

Filament

An icy moon with two distinct surface is:

Ganymede

Largest diameter (planetary satellites)

Ganymede

Larger than mercury moons

Ganymede, Titan

Define ice, gas, and dust

Gas and ice are the lighter non-metal elements like nitrogen, oxygen, and carbon and the molecules they form. If they are bound in a solid form we call them "ice". If not, we call them "gas". Dust is the heavier elements like silicon and metals like iron and nickel that are found in space as small solid grains. .

Let your imagination go wild and speculate on how the Milky Way would appear to us if the sun were relocated to deep in the bulge near the nucleus:

Here the stars are dense and dust relatively thin. We would be surrounded by so many stars that it would likely never get dark. There might be so many stars that the disk would be difficult to see and understand.

An unusual feature on Saturn is

Hexagonal cloud patterns at one pole

Halo stars orbiting close to the sun are called

High velocity stars

Neither Io nor Europa have impact craters while Ganymede and Callisto are covered with craters. Why the difference?

Io and Europa both have active surfaces and Ganymede and Callisto do not. Crater impacts on Io and Europa disappear as their surfaces get remade.

How does a star cluster, once created, encourage other star formation?

Interstellar gas must collapse to form stars. Radiation pressure from young stars and shock pressure from high mass exploding stars force gas clouds to collapse, thus creating a new generation of stars.

mnemonic used to remember the spectral sequence of stars arranged in order of temperature

Oh Be A Fine Girl Kiss Me!

The value for speed of light was first measured accurately by _______ who used eclipses of the _______ for his estimate.

Olaus Roemer moons of Jupiter

Where in the Solar System is it most likely that life could have arisen besides Earth? Explain your answer.

On either Mars or Europa since they both have or have had water. Titan is also suspect because of the nitrogen and hydrocarbon rich atmosphere.

There are two stars orbiting each other which means they are essentially the same distance away. One is blue and the other is red. They are also the exact same size. Which statement must be true? One star must be brighter than the other but that is the only difference One star must be hotter than the other but that is the only difference One star is both brighter and hotter than the other One star is both dimmer and hotter than the other

One star is both brighter and hotter than the other

synchrotron radiation

Radiation emitted when charged particles spiral rapidly in a magnetic field

Layers of sun from core to outside

Radiative zone Convective zone Photosphere Chromosphere Corona

a) Describe a radio galaxy

Radio galaxies are galaxies whose nuclei emit jets of material at high speeds. This material eventually slows as it loses kinetic energy some of which is radiated away as radio electromagnetic radiation. The jets of material are coming from supermassive black holes with accretion disks that heat surrounding gas to temperatures hot enough to boil it back into space.

Tidal forces keep ring particles from condensing into a moon when they are within the

Roche limit

Layers of Jupiter

Rocky Core Liquid "Ices" Helium and Liquid Metallic Hydrogen Hydrogen and Helium "surface"

Galaxies with flat disks but little or no gas and no spiral arms are

S0

Least dense

Saturn

Which type of galaxy has more angular momentum? (spinning motion) Ellipticals or Spirals?

Spirals

Describe the sequence of events that cause an intermediate or high mass star to explode.

When a critical density of iron builds up in the core, the core collapses under its own weight heating up and creating a burst of gamma rays that obliterate or "photodisintegrate" the iron nuclei. High-energy neutrinos are created in this process carrying large amounts of thermal energy away. Without this thermal energy to support the core, it collapses and "bounces" sending a shock wave through the star powerful enough to tear it to pieces in a supernova blast.

degeneracy

When electrons are compressed to the unnatural state of having their pressure not related to their temperature.

How do planetary nebulae form? Use the following words in your explanation: AGB star, helium shell burning, thermal pulses.

When low mass stars age, they become asymptotic giant branch (AGB) stars which are red giants burning both helium and hydrogen in shells. Near the end of their lives the density in the shells fluctuate and fusion alternately is active and dormant in each shell. When it becomes active in the helium shell it reignites in a helium shell flash which causes a thermal pulse that drives the star's outer layers off into space. The material driven off this way becomes the planetary nebula.

convection

When material is heated and moves taking the heat energy with it.

What is a pulsar and how are they different from pulsating variable stars?

When the stellar core of an intermediate mass star collapses to form a neutron star, its rotational speed increases according to the law of conservation of angular momentum. If it has a magnetic field (as it should) the effects of relativity on the magnetic field make it so that light itself can only escape through the north and south magnetic poles. As these poles sweep across our line of sight we see a pulse of light, hence the name pulsar. Typical pulsar periods are thousands of seconds to tens of seconds. Pulsating variable stars, on the other hand, are evolving horizontal branch, Red Giant, or AGB star that are passing through the "instability strip" of the HR diagram. These stars pulse in and out brightening and dimming in the process with periods of hours to months.

What is a white dwarf?

The core of a planetary nebula. It has huge surface gravity and a small size - roughly that of Earth.

Describe the corona. What is most unusual about it?

The corona is the tenuous atmosphere, spectacularly visible during eclipses, that is the outer layer of the sun. It's temperature is quite unsusal. Because it is very thin each particle in it carries a large amount of the energy passing through it from the chromosphere to space. Particle energy is temperature making the temperature of the corona is over a million degrees!

Explain a) what the cosmic microwave background is b) how it came into being and c) why is has lumps in it and why we care.

The cosmic microwave background (CMB) is blackbody radiation left from the Big Bang. For three hundred thousand years after the Big Bang, the universe was opaque. In other words, light could not travel very far without being scattered, absorbed, and re-emitted. In an era called recombination photons were free to fly into space without being altered. If we could have measured those photons at that moment, they would resemble those given off by a black body at a temperature of 10,000 °K. The universe has been expanding ever since, and because of red shifting, these photons now appear as if they were made from a black body with a temperature of 2.7 °K. According to Wien's Law, any object of this temperature emits most of its energy in the microwave part of the electromagnetic spectrum.

What is the cosmological principle and how does the Big Bang theory use it?

The cosmological principle is the assumption that the universe is isotropic and homogeneous. The Big Bang assumes it to be a correct principle so that what we observe is exactly like what is too far away to be observed.

promordial fireball

The mix of pure photon energy that emerged at the start of the universe.

Suppose you see the moon in the sky on two successive nights. How has its position changed with respect to the stars on the second night? Why?

The moon will be further to the east by about 12 degrees. This is because the moon orbits about Earth.

What causes the zones and belts on Jupiter and Saturn?

There are high and low pressure areas in the upper "atmosphere" part of Jupiter's surface. Jupiter's rapid differential rotation stretches these areas into bands. We see to deeper, darker-colored layers in the belts than we do in the zones.

spectral lines

The wavelengths where a specific element can absorb or emit light

Explain dark energy and the evidence for it. Does it have a relation to dark matter?

To explain the increasing expansion rate we have invoked a quantity called ΩΛ which represents "dark energy". This energy was actually predicted by Einstein's equations of the universe under general relativity but written off as a blunder. It has the feature of being an attribute of space itself. As space expands, this energy appears with it although we have no idea where it might come from. It has no relation at all to dark matter.

The tilt of Saturn's spin axis causes its rings

To seep to disappear every 15 years

Which are the largest diameter stars?

Top right on the diagram

The one way we can test our theories of solar fusion is

by measuring _neutrinos__________ created in the process.

The Jovian planets are made up mostly of the light elements __

hydrogen and _helium

Thermodynamic equilibrium is when

material has an unchanging temperature gradient. That is, the temperature is not the same throughout but whatever it is at any point, it is not changing with time.

Time/ temperature: 300,000 years/10,000K

primordial fireball, radiation dominance

Earth goes through different motions which are manifest to us in many different ways. A ___________ day is defined as being the time interval between when the sun is directly overhead and is exactly 24 hours.

solar, or synodic

Some meteorites are made of chondrules but most are either made of __ or__, or a mixture of both

stone or iron

Clusters of galaxies are in turn organized into larger groups called __________. These form a honeycomb like pattern surrounding empty or nearly empty ____.

superclusters voids

The reason Olympus Mons grew to be so large is

It resides over a former permanent hot spot. Mars, having no plate tectonics, never moved the volcano.

Small rocks fractured from asteroids are called

Meteoroids

differential rotation

The rotation of a star or planet at different speeds at its equator and poles.

sidereal day

The rotation period of Earth measured relative to the stars.

synodic day

The rotation period of Earth measured relative to the sun.

spectroscopy

The science of measuring light energy by wavelength.

greenhouse effect

The trapping of heat by carbon dioxide or other gases in Earth's atmosphere.

Slowest rotation

Venus (retrograde)

___ meteorites are rich in organic compounds including amino acids which are the building blocks of life

_Carbonaceous___chondrite__

The solar system is about 1 light day across. The Milky Way galaxy is about 100,000 light-years across. The Milky Way is about ____ times larger than the solar system.

36,500,000

Describe the morphology, population, and dynamics of the following parts of the Milky Way and list the types of objects found in each: Disk

A flat disk with gas, dust, HII regions, molecular clouds, gas clouds, dust, young stars and remnants of old stars like planetary nebulae and supernova remnants. The stars spin together with similar velocities in a manner called "differential rotation".

In a closed universe, the curvature of space-time is Parallel beams will The density parameter, Ω0, is

positive converge greater than 1

OB associations

collections of young, hot stars; irradiate the surrounding gas, turning it into an HII region

Time/ temperature: 1-2 billion years/20-13 K

era of recombination at end when CMB is formed _first stars and galaxies form

Ultimately the energy (in the proton-proton chain) comes from converting

mass to energy in accordance with the Einstein relation of E = mc2

In an open universe, the curvature of space-time is Parallel beams will The density parameter, Ω0, is

negative diverge less than 1

nucleus

The location of a supermassive black hole

electromagnetic radiation

All possible types of energy that can be emitted and absorbed by atoms.

When we solved the Drake equation in class, we assumed or colluded that

All stars like the sun have planets All stars with planets have one like Earth All Earth-like planets have or have had life The nearest civilization is about 100 light years away

When a full moon sets in the west

At sunrise

When a 1st quarter moon is directly overhead

At sunset

Which are the stars with the smallest diameters?

Bottom left on the diagram

Which are the lowest mass main sequence stars?

Bottom right on the diagram (has to be on the main sequence line)

comet

Conglomerates of ice and rock that orbit the sun in highly elliptical paths.

Most dense

Earth

Time/ temperature: 3 min/10^8 °K

H, He, Li nuclei created

Electron degeneracy is a phenomenon

In white draws that prevents carbon from fusing

Sunspots...

Increase and decrease in number in an 11 and 22 year cycle

Fastest rotation

Jupiter

Most moons

Jupiter

largest mass

Jupiter

light pollution

Light scattered through the atmosphere that degrades astronomical images.

zone

Light-colored high-pressure bands in Jupiter's atmosphere.

Jupiter's magnetic field is caused by

Liquid metallic hydrogen in the mantle

instability strip

The location on an H-R diagram where evolving stars pulsate.

Hottest surface

Venus

Roundest orbit

Venus

The planet with the hottest surface temperature is:

Venus

Magnitudes are a logarithmic expression of brightness. A magnitude difference of 1 means that the brightness ratio is a factor of 2.512. A magnitude difference of 2 means that the brightness difference is 2.512 x 2.512 = (2.512)2 = 6.3. A magnitude difference of 5 is (2.512)5 which is exactly 100. With this as a guide how much brighter is: The sun (m~-26.5) than a full moon (m~-12.5)?

Δm = 14; (2.512)14=400,000

Magnitudes are a logarithmic expression of brightness. A magnitude difference of 1 means that the brightness ratio is a factor of 2.512. A magnitude difference of 2 means that the brightness difference is 2.512 x 2.512 = (2.512)2 = 6.3. A magnitude difference of 5 is (2.512)5 which is exactly 100. With this as a guide how much brighter is: Venus (m~-4) than Pluto (m~15)?

Δm = 19; (2.512)19=40,00,000

Magnitudes are a logarithmic expression of brightness. A magnitude difference of 1 means that the brightness ratio is a factor of 2.512. A magnitude difference of 2 means that the brightness difference is 2.512 x 2.512 = (2.512)2 = 6.3. A magnitude difference of 5 is (2.512)5 which is exactly 100. With this as a guide how much brighter is: The limit for a small telescope (m~10) than the limit for the world's largest telescope (m~30)?

Δm = 20; (2.512)20=100,000,000

How much greater is the light-gathering power of a telescope with a 20 inch primary mirror than one with a 10 inch primary mirror?

(20/10)^2 = 4

Arrange the following objects by their distance from Earth.

(Closest) 1. Saturn (0.000015 light years, ly) 2. Pluto (0.0006 ly) 3. Betelgeuse (640 ly) 4. M13 (22,000 ly) 5. Center of the Milky Way (26,000 ly) 6. The Andromeda Galaxy (2.2 million ly) 7. Pices-Perseus Super Cluster (Farthest)

One star has a color index of B-V=-1 and another has a color index of +1. Which is the bluest?

-1

A star has a parallax angle of 0.25 arcseconds/ Therefore its distance is

1/0.25= 4 parsecs

One star has an apparent magnitude of +4. Another star has an apparent magnitude of +9. The ratio of their brightnesses is a factor of:

100 ((9-4 is 5, 5 parsecs))

The visible universe is about 14 billion light- years across. The visible universe is then __________ times larger than the Milky Way.

140,000

How much greater is the resolving power of a telescope with a 20 inch primary mirror than one with a 10 inch primary mirror?

20/10 = 2

The sun takes __ years to orbit once around the galaxy

220 million

How long does it take for the sun to orbit once around the Milky Way?

250 million years

The speed of light in a vacuum is approximately

300,000 km/sec

Draw a graph on the grid below showing the Hubble law relation out to a distance of 200 Mpc. Be sure to label the axes correctly. If the Hubble constant Ho = 70 km/sec per Mpc, a galaxy that is 5 Mpc away has a speed of _______ km/sec, and a galaxy that is 8 Mpc away has a speed of _560___ km/sec. On the other hand, if the speed of a galaxy is known (from the redshifted absorption lines in its spectrum), then Hubble's Law tells us the distance to that galaxy. This is how the distances to the farthest objects in the universe are measured. As an example, a galaxy with a redshift of 7000 km/sec is at a distance of ______ Mpc

360 560 100

Later it was found that all stars are about __ hydrogen __ helium __ everything else

75% 23% 2%

Explain what a black hole is and how curved space-time predicts that they can exist.

A black hole is a curvature in space-time so extreme that it essentially is a hole in space. Like taking a sheet of rubber and pulling it out at one place until it stretches so far it breaks. Since light beams travel along the curve lines, even light cannot find a way out of a black hole once it has formed.

prominence:

A bridge of material held in position above the solar surface. They can remain there for hours or days.

plage:

A bright area of higher temperature that often precedes the formation of sunspots. Sunspots may form within them

cepheid variable

A bright, pulsating horizontal branch star.

photon

A particle of light.

rich cluster

A very dense, highly populated cluster of galaxies

quasar

A very distant, star-like object with huge, broad emission lines. Probably the nucleus of a distant active galaxy.

neutrino

A very low-mass particle formed in solar fusion reactions that reacts only weakly with matter.

void

A volume of space where few, if any, galaxies are located

homogeneous

A word meaning "the same everywhere throughout."

isotropic

A word meaning "the same in all directions."

What is the diameter of the Milky Way?

About 150,000 light years

How far is the sun from the nucleus in the galaxy?

About 8 kiloparsecs or 26,000 light years

Why do we not see planetary nebulae that are older than 50,000 years?

After 50,000 years the planetary nebula diffuses back into the interstellar medium and is gone.

Carbonaceous chondrite meteorites contain

Amino acids

In what chemical form are Jupiter's nitrogen, carbon and oxygen?

Ammonia, methane, and water

annular eclipse

An eclipse of the sun that occurs when the angular diameter of the moon is less than the angular diameter of the sun.

supermassive black hole

An entity that is likely in the nucleus of most, if not all, galaxies

horizontal branch star

An evolved star that is burning helium to carbon in its core.

Explain how Isaac Newton's law of gravity did away with the old notion of "quintessence" and thus allowed for space to be completely empty (Note: not in book, get from lecture)..

Before Newton's law of gravity it was believed that planets were kept in their orbits by contact with quintessence: a material that filled all of space. Planets were like marbles embedded in glass shells with the quintessence "glass" keeping them at their distance from the sun. The law of gravity explained how planets could actually be always falling but still remain the same distance away.

Asteroids are found throughout the inter solar system but especially:

Between Mars and Jupiter

Which of the following is NOT a surface feature on Mars? A. Northern Lowlands B. Caloris Basin C. Can't remember lol D. Southern Highlands E. Ice-capped poles

Caloris Basin

geocentric

Centered on Earth

radio lobe

Clouds of low density gas often found glowing faintly on either side of an AGN

sunspots

Dark areas on the sun that are cooler than the surrounding photosphere.

Molecular clouds contract down to form __ where star clusters will be created

Dark nebulae

belt

Dark, reddish, low-pressure bands in Jupiter's atmosphere.

Hershel and Kaptyn incorrectly concluded the sun was near the center of the universe because they did not know about

Dust

reflection nebulae

Dusty nebula in which starlight has pushed gas but not dust away.

Galilean satellite

Either Io, Europa, Ganymede or Callisto

Earth's magnetic field is from

Electric currents in the outer core

Supernovae are responsible for

Elements heavier than hydrogen found in nebular Helping to create new stars via their shock waves

Describe heliocentric Copernicus cosmology

In Copernicus' solar system, the planets travel in circular orbits around the sun. In this system retrograde motion results when Earth overtakes and passes a more slowly moving superior planet. When this happens planets appear to reverse temporarily their usual eastward direction of motion, and move backwards to the west. It is an illusion, the planet does not really go backwards.

deferent

In Ptolemy's geocentric solar system, the large circle on which a planet's epicycle moved around Earth

epicycle

In Ptolemy's geocentric solar system, the small circle on which a planet moved

Time/ temperature: 10^-35 sec/10^27 °K

Inflation, strong nuclear force freezes out

Suppose fusion in the core stopped abruptly. Explain why the intensity of light coming from the sun would not change as abruptly.

It takes a long, long time for the energy to work its way to the surface. If fusion in the core were to suddenly stop it would take millions of years for the last photons generated to work their way to the surface. And it would take an additional several billion years for the sun to fade out. For example the earth has no internal heat source but has been cooling for ~ 4.5 billion years and it still is hot enough in the center to be molten.

What is liquid metallic hydrogen and where does it come from?

Liquid metallic hydrogen is hydrogen that has undergone a change of state from gas to a liquid. When hydrogen undergoes intense pressure the electrons can dissociate from the protons and migrate around like in a metal. This makes electric currents possible.

Which spectral type designates the coolest stars? A B F K M

M

Jupiter has a striped appearance because:

Material at different latitudes rotates with different speeds. High and low pressure areas have different colors. It's fast overall rotation stretches high and low pressure areas into stripes

flare:

Material that shoots rapidly out into space. Flares cause auroras if their material hits Earth.

Most eccentric orbit

Mercury

Where is the center of the expansion?

Nowhere visible to us. If there are higher dimension then the center would be visible to someone who lives in one. If there are no higher dimensions then the center does not exist.

Star type that lives the shortest life is

O

Why does fusion occur only in the core and not in the outer layers?

Only in the core is the pressure great enough to confine the atoms close enough for fusion to take place

Which shapes Earth's surface the most? Asteroid impacts Meteoroid impacts Plate tectonics Global warming

Plate tectonics

Hubble tuning fork diagram.

Plus irregular galaxies at the far right.

Describe a quasar.

Quasars are "Quasi-stellar radio sources". Originally thought to be stars emitting radio radiation, they were later discovered to be the nuclei of very distant galaxies. Like radio galaxies, they often have jets of radio-emitting gas coming from their nuclei. They also have broad emission lines.

The layer of the sun nearest to the core is the

Radiative zone

The effort to find extra-terrestrial life is called

SETI

Galaxies with large bulges ad tightly wound, smooth arms are

Sa

Limb darkening is from:

Seeing to shallower depths at the sun's edges

Describe a Seyfert galaxy

Seyferts are nearby galaxies with nuclei that look like quasars. They have broad emission lines but often no radio emission.

Charged particles moving rapidly in a magnetic field five off

Synchrotron

liquid metallic hydrogen

That which is responsible for Jupiter's magnetic field

particle horizon

The "edge" of the universe. Light beyond this has not reached us yet.

photosphere

The "surface" of the sun

sunspot cycle

The 22 year period on the sun during which sunspots increase, decrease, change polarity, increase and decrease again.

How does the Big Bang theory of cosmology resolve this paradox?

The Big Bang says that the universe has not existed forever. It had a distinct beginning about 14 billion years ago called the "Big Bang". Therefore light from any object more than 14 billion light years away has not had time to reach us. The other part of the solution is that the universe is expanding. So the light we receive from distant galaxies is redshifted to lower and lower energies. If light from the "edge" of the universe could reach us, it would have zero energy.

List the essential ideas of the Big Bang theory.

The Big Bang was not an explosion of matter into empty space, like the explosion of abomb. Instead, it was an emergence of space and time filled with pure energy where before none of this was present. The point from which is emerged is called the "cosmic singularity." The resulting expansion is still going on today carrying galaxies away from one another.

AGN

The class of all objects having high energy radiation coming from their nuclei.

maria

The dark, relatively smooth areas on the moon; Latin for "sea".

corona

The high-temperature outermost layer of the sun.

solar nebula

The material from which the solar system formed.

light curve

The measure of a variable star's apparent magnitude as it brightens and dims with time.

Explain how the planets obtained their atmospheres.

The planets when forming first collected gas in "primary atmospheres". The Jovian planets still have primary atmospheres but the terrestrial planets lost theirs because they have so little mass. Venus, Earth and Mars gained "secondary atmospheres" later by capturing comets and by outgassing from the planet interiors.

zenith

The point directly overhead.

accretion

The process of acquiring material.

chemical differentiation

The sinking of denser elements to the center of a young molten planet

cosmology

The study of the universe as a whole.

Briefly describe the major features and interesting aspects of Uranus.

The surface was nearly featureless when Voyager II passed by. Zones and belts can be faintly seen from the HST now, though. It has a greenish color from atmospheric methane. The tilt of its axis is 98 degrees from vertical meaning that Uranus rolls along in its orbit. Its magnetic field is offset from the planet center.

Describe the morphology, population, and dynamics of the following parts of the Milky Way and list the types of objects found in each: Nucleus.

The very center of the galaxy. Stars there move with very high speeds near an unseen body. There are clouds that seem to spiral in toward that same point. A strong magnetic field exists there too. All of these evidences indicate a black hole with a mass greater than a million times that of the sun is there.

magnetosphere

The volume surrounding Earth defining the limit of influence of its magnetic field.

What is odd about the planets that have been discovered?

They are high mass and probably Jovian yet are in elliptical orbits that are close to the host star, unlike the planets in our solar system.

We, living far away from a black hole, will see ___ at the event horizon of a black hole

Time slow down and stop

A body with liquid pools of methane on its surface is

Titan

Thickest atmosphere moon

Titan

Which star's absorption lines are the thinnest?

Top left on the diagram

Describe the sequence of fusion in the core of an intermediate or high mass star after it becomes an AGB star.

Unlike the low-mass stars, high-mass stars have enough gravity pressure to fuse carbon into neon. From there the star will also burn neon to oxygen and magnesium and then to silicon. When silicon burns (in only one day!) it leaves a core of unburnable iron. At this point there is an "onion" like nesting of concentric shells of different fusion volumes in the core. The star, powered by the energy from these layers of fusion, expands to become a supergiant.

We use distances from parallax measurements to make H-R diagrams. In turn, an HR diagram is used to find distances to stars so far away we cannot measure their parallax angles. Explain how HR diagrams are used to find distances.

We measure the spectral type or color index of the star. Then we find its luminosity class. Knowing these things we can uniquely place it on an H-R diagram and read the absolute magnitude from the vertical axis. Knowing the absolute magnitude, we can measure the apparent magnitude, see how much fainter it is than the absolute magnitude, and use that difference to find the distance. The larger the difference, the farther away it is.

What causes the difference between these two periods? (Solar vs sidereal?)

When Earth spins on its axis it also orbits the sun. The advancement along the orbital path causes the stars to reappear at the same location after one spin slightly sooner than the sun does. This difference is 4 minutes a day.

conjunction

When a planet lines up with the sun in the sky.

Explain what happens to a star from when it uses up all the hydrogen in the core to when it begins to fuse helium in the core.

When a star uses the hydrogen in its core, it leaves the heavier helium behind as "ashes" and continues burning hydrogen in a shell outside the core. While it does this, its brightness increases and its surface temperature decreases. The star becomes a red giant.

It is likely that the major source of meteoroids is collisions between ___since the two major types of meteoroids resemble fractured pieces of crust and core material.

__asteroids____

In a flat universe, the curvature of space-time is Parallel beams will The density parameter, Ω0, is

flat emain parallel exactly

Theory virtually demands that the geometry be Results of measuring lumps in the cosmic background radiation indicate that the universe geometry is

flat flat

In many Sa and Sb galaxies there are two magnificent arms winding their way out from the nucleus in a symmetrical manner. These galaxies are called

grand design spirals

The most geologically active moon is

io

When meteoroids fall to Earth, the streak of light they make is called a

meteor

There are three possible geometries of the universe:

open, flat, and closed.

Galaxies move very rapidly in the interiors of the dense clusters. In fact they move so fast that astronomers conclude

there is once again dark matter located in the centers of these clusters pulling the cluster members into faster orbits. The galaxies move rapidly but do not leave the cluster because the gravity from dark matter keeps them bound.

Time/ temperature: 13.8 billion years/2.7 K

today

Pulsars are

Spinning neutron stars

blackbody

A perfect absorber and radiator of electromagnetic radiation.

Seyfert galaxy

A nearby galaxy with a quasar-like nucleus

Explain what a parsec is.

A parsec is a distance measure determined by the parallax of a star which is the shifting of its position against the background sky every 6 months. The distance is found by inverting a star's parallax when the parallax is expressed in seconds of arc. One parsec is equal to 3.26 light years.

meteor shower

A phenomenon seen when Earth passes through the orbit of a burned out comet

extrasolar planet

A planet orbiting about a distant star.

inferior planet

A planet that orbits closer to the sun than Earth

superior planet

A planet that orbits farther from the sun than Earth.

Describe hydrostatic equilibrium.

Hydrostatic equilibrium is when material has an unchanging pressure gradient. That is, the pressure is not the same throughout but whatever it is at any point, it is not changing with time.

SETI

The organized effort to find life elsewhere in the universe.

disk

The part of the Milky way that has on-going star formation

Explain the "particle horizon and its physical significance

The particle horizon is the farthest we can see. It exists because the universe had a beginning and thus a definite age. Light from distances farther away from the particle horizon have not had time to reach us yet.

celestial pole

The place in the sky that Earth's axis points toward (can be either north or south).

aphelion

The point in its orbit where a planet is farthest from the sun

perihelion

The point in its orbit where a planet is nearest the sun.

opposition

The point where a superior planet is as far away from the sun as it can be (as seen from Earth).

greatest elongation

The point where an inferior planet is as far away from the sun as it can be (as seen from Earth).

A glowing blackbody produces a 111111 spectrum of electromagnetic radiation. If this radiation passes through a rarified gas cloud, then it will have 2222 created in it. When the gas re-radiates the subtracted light, it creates a(n) 3333 spectrum. By studying spectral features, astronomers can determine the chemical composition and temperature of the radiating body and gas that the light passes through.

1 continuous 2 absorption lines 3 emission line

Ganymede:

1) Largest moon in the solar system 2) Two different types of terrain 3) Darker terrain is older

Callisto:

1) Old, pockmarked, icy surface 2) Interior is NOT differentiated 3) Geologically dead.

Stars with the least amount of "metals" are population

2

One star has an apparent magnitude of +4. Another star has an apparent magnitude of +5. The ratio of their brightnesses is a factor of:

2.512 ((5-4 is 1, 1 parsec))

Suppose you have a telescope with a focal length of 40 inches. What is the magnification when using an eyepiece with a focal length of 2 inches?____________. What is the magnification when using an eyepiece with a focal length of 0.5 inches? ___________.

20 80

There are eight classical planets and at least three dwarf planets, Ceres, Pluto, and Eris, orbiting the sun. In addition, there are hundreds of thousands of 6666666 called asteroids orbiting between the planets of 11111111111 in the 22222222. This is a semi-regular, thin ring around the sun that is made up of material that didn't coalesce into a planet. Not all are in this band. A group called the 333333333 , are in elliptical orbits that take them inside the orbit of Earth. Therefore it is certain that Earth, the moon and Mars have been hit by an asteroid in the past. In fact, in the last decade four asteroids have passed within 6 million km of Earth. A layer of sediment rich in the element iridium (which is common in asteroids) supports the idea that an asteroid impact may have caused the dinosaurs to become extinct.

6: Planetesimals 1: Mars and Jupiter 2: Asteroid belt 3: Apollo Asteroids

Can a penny held at arm's length completely cover the sun? A penny is about 0.75 inches in diameter.

A penny held at arm's length is about a degree in diameter and can easily cover the sun.

limb darkening

A change in the appearance of the sun at the edge of the solar disk

HII region

A cloud of ionized hydrogen. Formed when young stars heat the surrounding gas.

Kuiper belt

A collection of comets in the plane of the solar system, located beyond the orbit of Pluto

poor cluster

A collection of galaxies like the one the Milky Way belongs to.

absorption spectrum

A continuous spectrum of light missing energy at a few wave lengths.

dark nebula

A cool collection of gas and dust that will eventually become a star cluster.

luminosity class

A designation that separates dwarf stars from giant stars.

Material evaporating from a comet nucleus creates:

A dust tail A gas tail Material that can be part of a meteor shower

TransNeptunian Object

A dwarf planet orbiting beyond Neptune

Describe the morphology, population, and dynamics of the following parts of the Milky Way and list the types of objects found in each: Bulge

A flattened spherical distribution of old stars with some young stars too. It is the "hub" of the Milky Way. Its stars orbit with speeds that a solid body would have. It is elongated into a bar shape.

proton-proton chain

A fusion process in which protons bond together to ultimately form helium

radio galaxy

A galaxy emitting large amounts of energy at long wavelengths

Explain what a "gravitational lens" is and what it proves about the general theory of relativity.

A gravitational lens occurs when light from a distant galaxy or quasar is redirected toward us by the curvature of space- time near a massive galaxy or cluster of galaxies. it is a stark confirmation of the general theory of relativity that says gravity is actually a curvature in space-time.

Great Dark Spot

A high-pressure bulge in Neptune's southern hemisphere

blazar

A highly variable galaxy nucleus of which BL Lac is one.Their light is highly energetic and their spectra are featureless.

asteroid

A large, irregularly shaped rocky object orbiting the sun, mostly between the orbits of Mars and Jupiter.

Write Kepler's second law:

A line connecting the sun and planet sweeps out equal areas in equal times. (Planets move slowest when farther away from the sun. This is such that the two areas shown equal each other if the time interval they represent in the orbit is the same.)

apparent magnitude

A logarithmic measure of how bright a star appears to be.

absolute magnitude

A logarithmic measure of how luminous a star really is.

Great Red Spot

A long-lived high-pressure bulge in Jupiter's southern hemisphere.

Is the same true for a total eclipse of the moon? i.e. is it only visible from certain places on Earth? Why or why not.

A total eclipse of the moon is when the entire lunar surface is in the umbra of Earth's shadow. Being in the shadow, it will be dark no matter where on Earth you are looking from. Of course since the moon is only visible to half of Earth at a time, lunar eclipses also will only be visible to half of Earth as well.

blackbody curve

All wavelengths of light emitted by a blackbody.

open cluster

An irregularly shaped cluster of stars.

An interesting feature of Uranus is

An offset magnetic field

What is the evidence for liquid water having been on Mars in the past?

Ancient stream channels and flood plains have been imaged by orbiting spacecraft. These same spacecreaft have also imaged darker "seepages" coming from crater and valley walls. And sedimentary-type rock including conglomerates imaged by Opportunity have been discovered on the surface.

standard candle

Any class of objects with a uniform luminosity used to determine distance.

A star burning hydrogen to helium in a shell and helium ot carbon and oxygen in a shell is a (an) ____ star

Asymptotic Red giant branch

Describe through words and pictures how sunspots form according to the Babcock magnetic- dynamo model. Explain how this leads to the observed 22 year sunspot cycle.

At the beginning of a sunspot cycle the magnetic field lines run north-south. After a few revolutions they are pulled horizontally in an east-west direction because the equator rotates faster than the poles.. At this time the field strengthens at high latitudes. Sunspots first appear at these high latitudes and their numbers are few. As the cycle progresses the subsequent sunspots are found at lower latitudes, closer to the equator, and their numbers increase. This is the sunspot maximum. As the cycle progresses the sunspots appear closer yet to the equator but their numbers decrease. Finally the sunspots disappear altogether as the magnetic field also disappears. The sequence then repeats but with the polarity of sunspot groups reversed.

a) How does the rotation curve of galaxies lead to the concept of "dark matter"

At the outer edge of the galaxy star orbits should become "Keplerian". That is, their speeds should begin to diminish with distance in accordance with Kepler's laws. But they don't. So we conclude that there is increasing gravitational force with distance from the nucleus. This means there is a source of the gravity—dark matter—that increases with radius as well.

Describe an aurora and explain how they are created.

Auroras are airglow in the high northern or southern latitudes. They are created when high energy charged particles from the sun stream out from solars flares, striking Earth. Earth's magnetic field shunts them to the northern and southern poles where they strike the upper atmosphere causing it to glow

The particle NOT created in fusion is

Axions

Draw a continuous spectrum, an emission-line spectrum, and an absorption line spectrum.

BE ABLE TO DO IT YOU HEATHEN

What did Herschel and Kapteyn conclude about the sun's position in the Milky Way? Why were they wrong?

By counting stars at different positions int eh sky, they concluded the sun was at the center of a universal distribution of stars. They were wrong because they did not realize that dust in the Milky Way disk was diminishing light from distant stars. All the stars they were counting were close to the sun.

heliocentric

Centered on the sun

List and briefly describe the four processes that shape planetary surfaces. Indicate which processes are most influential on Mercury, Venus, Earth, and Mars.

Cratering is from objects impacting. Tectonics is when the surface floats on molten material and moves about as plates. Volcanism is molten material erupting from beneath the surface. Erosion is when an atmosphere wears surface features down. Mercury is most influenced by cratering, Venus by volcanism, erosion, and perhaps tectonics, Earth by erosion and tectonics with some volcanism, and Mars by volcanism, cratering, and erosion.

Water on Mars:

Created floodplains and river channels Likely used to be in the northern lowlands

Time/ temperature: 10^-12 sec/10^13 °K

Creation of nucleons, Breaking of symmetry, _Emergence of matter, weak force freezes out

Which is NOT a class of meteorites? Carbonaceous chondrites Differentiated luddites Iron/nickel Stone/iron mix Stone

Differentiated luddites

Earth has very few craters while the moon has many. Explain why they are so different.

Earth's surface is subject to resurfacing by erosion from the hydrological system (weathering) and plate tectonics. Both of these processes have worked to remove the craters created in Earth's formative years. The moon has no such processes and so the craters have persisted through time.

Explain how the elements that formed Earth were created and incorporated into the solar nebula.

Elements between helium and iron are formed from fusion in the cores of intermediate or high mass stars. At the moment these stars collapse and explode as supernovae, neutrons captured by iron nuclei create elements up to uranium. These elements are scattered back into space by the explosions where they become dust and eventually planets.

Galaxies with little or no gas which are shaped like rugby footballs are

Elliptical

Roundest shape (planetary satellites)

Europa

Europa:1)

Extremely round 2) Lots of liquid water 3) Ice rafts on the surface

Explain how we think the Milky Way galaxy formed. In your explanation describe population I and population II stars.

First there was a huge collection of gas. It collapsed onto pockets of higher density each with about the mass of globular clusters or larger. Stars began to form as the collapse continued. These stars would form globular clusters and are population II stars which lack metals. As the collapse continued, the highest mass stars exploded as supernovae sending out elements heavier than hydrogen and helium (the "metals") in to the surrounding gas clouds. Many of the star clumps gravitated down into the center to form the bulge. Most of the remaining star clumps and essentially all of the gas collapsed down to form the disk.

a) List the four layers of Earth's atmosphere and indicate which one contains the weather.

From the surface of Earth going up, they are the troposphere, stratosphere, mesosphere, and thermosphere (The thermosphere is also called the ionosphere). The weather takes place in the troposphere.

Explain why elliptical and spiral galaxies have different shapes and different colors.

Galaxies which formed from slowly rotating clouds collapsed quicker. In these the initial star formation rate was high, then quickly died out. Today we see these galaxies as the older ellipticals. Elliptical galaxies have little rotation. Their stars are in "radial" orbits that plunge in and out through the galaxy center. Having an older population, they look redder. Galaxies that formed from rapidly rotating clouds collapse slower into a disk shape. These galaxies are the spirals. Here the star birth rate is low but proceeds for a longer time and is still ongoing. So they contain the higher mass blue stars and look bluer than the ellipticals.

Explain why the stars in globular clusters have the colors and absolute magnitudes that they do.

Globular cluster stars are evolved red giants, horizontal branch stars, and low-mass main- sequence stars. The red giants form a population of the brightest red stars in the cluster. The horizontal branch stars form a population of blue stars that are a bit less luminous than the red giants. The low-mass main-sequence stars form a faint population of reddish stars

Smallest stars, largest stars. Smallest mass main sequence stars. Highest stars, coolest stars, hottest stars, SUN.

Go find the diagram and practice.

Stars will form when __ causes gas clouds to collapse

Gravity Supernova shock waves Density waves in galaxy arms Radiation pressure

List the possible fates of the universe. Draw a graph if it helps.

Gravity only pulls matter back together. Therefore, if gravity is the only force that operates on cosmic scales then the expansion of the universe should decrease with time. The critical density is the value of matter density sufficient to halt the expansion. This value is not very large, only an average of six or seven hydrogen atoms for every cubic meter of space. If density is less than this the universe will expand forever (green line). If it is exactly this value it will expand forever while asymptotically approaching stopping (violet line). If it is greater than this the expansion will reverse and the universe will contract (blue line). If there is a force that pushes against gravity then it can increase expansion speed with time (orange line). If nothing increases or decreases the expansion speed then it will simple expand forever at the same rate as now (black line).

a) What are "high velocity stars" and how did they get that name?

High velocity stars are stars from the halo that have drifted into the disk. As the earth zooms past them in a faster orbit, they appear to be going backward at a high rate of speed. So we call them "high velocity" stars even though it is the sun that is really going faster.

granules

Hot cells of gas that rise and fall in the photosphere

When stars get older, the shells around the core burn __ the core alone did when they were younger

Hotter than

Compare and contrast novae and x-ray bursters.

If a white dwarf has a close companion that is evolving into a red giant, the companion will deposit material onto the white dwarf's surface. This material will compress and heat up under the crushing gravity. When the temperature is high enough, the layer will ignite fusion and there will be a thermonuclear blast on the surface. The star will brighten and become a nova. If the same thing happens on the surface of a neutron star, the greater gravity causes the energy to be given off as higher energy x-rays and the object is called an x-ray burster.

The special theory of relativity predicts that nothing can travel faster than the speed of light. However, under what circumstances can it travel slower than this?

If it is in a denser medium, such as glass, it will move slower. This change is speed is what causes light to refract.

How does the rotation curve lead to the "winding dilemma?

If stars have different orbital periods, then any arms formed by stars will wind into a tight spiral pattern in a billion years or so

What are neutron stars and how do they relate to the end of the life of an intermediate mass star?

If the core of a collapsed intermediate mass star has a mass between 1.4 and 3.0 solar masses, the collapse will push all the atomic electrons into their protons creating a giant ball of neutrons called a "neutron star".

When stars evolve past the red giant stage, they reach a point where heat in the core expands the outer envelope beyond the point supported by hydrostatic equilibrium. The outer envelope expands and thins, allowing interior heat to escape. The star cools down and contracts. The contraction thickens the outer envelope enough to trap excess heat again. The outer envelope expands and the cycle repeats. Therefore, stars at this stage pulsate. This pulsation can go on for millions of years. Explain which stars these are and why this natural occurrence is a boon to astronomy.

If they are high mass stars, they are Cepheids. If they have lower masses, they are called RR Lyrae stars. Their pulsation periods are proportional to their absolute magnitudes. So we can measure their pulsation periods, find out their absolute magnitudes, measure their apparent magnitudes, and calculate their distances.

Describe geocentric Ptolemy cosmology

In Ptolemy's solar system, Earth was at the center. The planets pivoted around a small circle called an epicycle. This small circle moved around Earth on a large, perfectly round circle called a deferent. Retrograde motion occurs when the backward motion on an epicycle is greater than the forward motion along the deferent.

How is the Hubble Law consistent with an expanding universe?

In an expanding universe all galaxies see all other galaxies that are not gravitationally bound to them receding away. Galaxies that are farthest away are seen to recede faster than closer galaxies in a linear fashion. This is what we see in the Hubble Law.

Explain how the Big Bang theory says matter came into being. Why is this a challenge to understand?

In the early universe just after the Big bang, there was nothing but high energy photons. High energy photons of light can and do spontaneously convert into particle and anti-particle pairs. They then usually recombine and revert back to photons. At some point as the universe expanded more matter than antimatter was created so that after the antimatter all annihilated, there was matter left over. This is called the "breaking of symmetry."

a) Describe the rotation curve of the Milky Way disk from the nucleus out to the edge. Draw a sketch as part of the explanation.

In the inner portion the curve increases linearly with distance. This is like a solid wheel would spin. Then the speeds settle to a roughly constant value with distance. This is the "differential rotation" region. Stars in inner orbits have shorter periods than stars in larger orbits.

What is inflation and what significance did it have in the early universe?

Inflation refers to a time just after the Big Bang when space expanded by an unbelievably huge amount. The expansion was faster than the speed of light and carried material well beyond the particle horizon. It made the CMB as smooth as it is seen today and has hidden from our view most of the universe.

Briefly describe the major features and interesting aspects of Neptune.

It also has a methane rich atmosphere like Uranus, but is a darker blue because it is colder. It has high wispy methane clouds and a dark spot similar to Jupiter's red spot that comes and goes. Its magnetic field is offset from its center.

According to the general theory of relativity Earth orbits the Sun because:

It is moving straight through curved space time

Let your imagination go wild and speculate on how the Milky Way would appear to us if the sun were relocated toa) the outer edge of the disk:

It would not appear very different from what it looks to us now since interstellar extinction blocks nearly all starlight from stars beyond a thousand light years or so. The Milky Way would appear basically unchanged as from any location within the disk that is outside the bulge.

The sun is in thermal equilibrium, therefore

It's temperature profile does not change with time

Jovian planets examples

Jupiter, Saturn, Uranus, Neptune

molecular clouds

Large collections of very cold gas and dust.

What is the connection between the liquid metallic hydrogen on Jupiter and Saturn and the fact that both these planets have auroras?

Liquid metallic hydrogen creates a magnetic field which is quite strong in these two planets. This in turn directs the solar wind particles to the poles just like it does on Earth, creating auroras.

What is the main reason some stars end up as planetary nebulae and other stars explode?

Low mass stars are not able to fuse elements heavier than carbon and oxygen and never build up iron cores. These stars still get very hot and "boil" off their outer layers in a series of thermal pulses creating planetary nebulae. The higher mass stars create iron cores which collapse creating an implosion that rebounds into an explosion.

Three stars have absolute magnitudes of -2, 0, and 2. Which is the most luminous?

M= -2

dark matter

Matter that reveals itself only through its gravitational attraction.

Smallest mass

Mercury

Fewest moons

Mercury and Venus

Compare and contrast Mercury's surface with the moon's surface.

Mercury's surface looks similar to the moons except the cratering is more uniform. The moon has heavily cratered highlands and lightly cratered maria. Mercury has rolling planes interspersed with craters.

Terrestrial planets examples

Mercury, Venus, Earth, Mars

When a 3rd quarter moon rises in the east

Midnight

Coldest surface temp

Neptune

What do we think the actual fate of the universe will be and why do we think this?

Observations of distant type Ia supernovae indicate that the current expansion of the universe is speeding up with time, not slowing down! So there must be a force causing this.

When a new moon is directly overhead

Noon

Sketch Earth's interior and label the layers. Explain how we know that it is layered like this.

Outer layer to inner: Crust, asthenosphere, mantle, outer core, inner core. Seismic waves diffract off the core creating shadow zones for both the pressure and shear waves. Their locations and sizes are determined by the size and density of the outer and inner cores and the fact that the outer core is liquid.

Write Kepler's third law and explain what it means:

P2 = a3. This means that the period of a planet, in years, when squared, equals the semi-major axis, in AU's, cubed

Explain with the use of a diagram why some constellations seen from Provo are circumpolar and some are never visible, yet from the equator all constellations are visible at some time during the year.

PRACTICE DRAWING A DIAGRAM! As a person's position on Earth shifts close to the equator, the circumpolar cone gets smaller and the nonvisible southern cone in the south also gets smaller. Right at the equator they both disappear which means all stars are visible from the equator.

Parallax (distance)

Parallax is a measure of the seasonal shifting of a star's position against farther stars or galaxies. The closer the star, the greater is the angular distance it shifts. We use it to find distances to stars that are up to 1,000 pc away.

Dwarf planets are mainly found:

Past Neptune

Time/ temperature: 10^-43 sec/10^32 °K

Planck time. Gravity "freezes" out

Stars with the mass of the sun become:

Planetary nebulae White dwarfs Black draws Red giants

Write Kepler's first law:

Planets orbit in ellipses about the sun, with the sun at a focus.

Spiral arms are locations of

Recent star formation

Saturns rings

Saturn's rings are made of small pieces of __ice_____ and __rock_____. They are very thin, only about 2 km thick. A ring and not a planet formed around Saturn because the ring material orbits inside the __Roche___ __limit_______ and tidal forces prevent any individual rock from growing to a size greater than 10 meters across. A gap between the A and B rings called the _Cassini_____ ___division_ appears to be empty when seen from Earth, but in reality it is filled with small particles. A twisted and braided ringlet is the _F_ ring. Its shape is determined by several _shepherd______ __satellites_ whose gravity preserve the ring's shape and identity.

Draw a model of a black hole, accretion disk, jet, and synchrotron radiation as we believe they exist in active galactic nuclei. Use it to explain the following: radio galaxy, seyfert galaxy, quasar, and blazar.

See figure to the left. Radio galaxies are when we see the jets in the plane of the sky. Blazars are when we see the jets coming at us. Seyfert galaxies and quasars are when we see the jets in between these two extremes. Quasars are also more luminous and farther away while Seyferts are closer and generally not so luminous. spiral galaxies their jets are often or usually obscured. Radio galaxies are evolved quasars in elliptical galaxies with little gas to impede the jets which then fly out of the galaxy forming radio lobes. The general idea is that quasars and blazars are supermassive blackholes in the early universe when there was plenty of gas to form large accretion disks. So quasars have large bright disks and jets that likely do not go very far before obscuring material inhibits their flow. Seyfert galaxies are evolved quasars with smaller accretion disks. Being common in

Explain why the turn off point on an HR diagram of a cluster is related to its age.

Since higher mass stars evolve off the main sequence faster, the location on an HR diagram where the stars are just beginning to evolve off gives the time since stars of that mass were created. This is the age of the entire cluster since stars of all masses are created in a cluster at the same time.

Which of these is a significant feature making up the chromosphere:

Spicule

shepherd satellite

Small moons that maintain the shape of rings around Saturn and Uranus

Write the Drake equation, explain each factor of it, and use it to explain what our chances of contacting other life are.

So our chances of communication aren't great but they are not zero either.

Magnetic fields around protostars five rise to __ that drive material back out into space

Solar winds

The graph below tells us

Space is expanding

HR diagrams can be used to find distances. When used this way, we measure __ and read the __ from the HR diagram.

Spectral type, absolute magnitude

using HR diagrams (distance)

Spectroscopic parallax refers to finding a star's absolute magnitude from its placement on an HR diagram. After finding the absolute magnitude, we measure the apparent magnitude, for a distance modulus and use this to find the distance. This method is good for finding distances to stars within the Milky Way galaxy.

Captain Picard, in an effort to escape from a Romulon warship, decides to send the Enterprise through a black hole. As he approaches the black hole, though, he is puzzled because the Romulons appear to him to be speeding up/slowing down (circle one). The Romulons in turn see the Enterprise speed up/slow down (circle one) and continue to pursue. An alarmed Data, knowing physics better than Captain Picard, arrives at the bridge and directs the space ship away. "We must not cross the _event horizon____________" he says, "Beyond that, even_light_ cannot escape! So the Enterprise escapes but the poor Romulons who never took physics 127 plunge into the black hole. The Romulon captain, before falling in, looks behind and sees all_time___ pass away before falling in. From Captain Picard's viewpoint, the Romulon ship a) remains outside the black hole and never does fall in or b) falls quickly inside the black hole and disappears from the known universe (circle one).

Speeding up Slow down event horizon light time remains outside the black hole and never does fall in

Describe the morphology, population, and dynamics of the following parts of the Milky Way and list the types of objects found in each: a) Halo

Spherical in shape with a diameter of about 150,000 light years. It consists of old red stars in slow, orbits that plunge through the disk and bulge. About 1% of these are in old, round globular clusters.

How is the winding dilemma solved?

Star orbits do not define the spiral patterns. Instead they are "density waves" that move at slower speeds. The desnity waves are locations where stars slow down, gas piles up, and star formation occurs. The arms are defined by young O and B stars and the gas clouds they irradiate.

Describe the general distribution of stars, gas, and dust in the disk of the Milky Way:

Stars are everywhere throughout the disk. In the spiral arms there is perhaps 5% more but that is all. These stars are mainly population I with higher metals and so are a younger population than, say, in the halo. The disk contains many very young stars in star clusters. Gas clouds are also everywhere throughout the disk. They tend to be very large and contain a huge amount of matter - more than is currently tied up in stars. In with the gas in the galaxy disk are dust grains. These grains are made of all the elements that are not in gaseous form in space - basically the metals plus carbon. It blocks starlight creating interstellar extinction. It is prevalent we cannot see distant stars as was explained in question 1.

The following diagram shows how: (go look)

Stars change in color and luminosity when transitioning from protostars to stars

Describe star formation using these terms: molecular clouds, dark nebulae, gravitational contraction, nuclear fusion, evolutionary tracks, HII region, OB association, bipolar outflow, protostar.

Stars first begin to form deep inside cool aggregates of gas and dust called giant molecular clouds. These condense to smaller parts called dark nebula. Dark nebula break into much smaller fragments inside of which form protostars. The energy source of a protostar is gravitational contraction. When the energy source becomes nuclear fusion we call it a main sequence star. As a protostar shrinks to become a main sequence star, it follows a path on an HR diagram called an evolutionary track. While settling onto the main sequence it pushes a considerable amount of material back into space often as a bipolar outflow. Once stars emerge to form a young cluster, they irradiate the surrounding gas, turning it into an HII region. The young group of stars is called an OB association. As it gets older it pushes the gas away leaving dust behind to form a reflection nebula. Once the gas and dust are mainly gone or collapsed to form planets, the cluster is called an open or galactic cluster.

Earth's atmosphere: Is the same thickness as Venus' atmosphere Started out as CO2 and evolved to have O2 Has a region, the thermosphere, where clouds and weather take place Is steadily getting colder with time

Started out as CO2 and evolved to have O2

What is the universe expanding into?

Strictly speaking it does not have to expand into anything. However your instructor is most comfortable with it expanding into a higher dimension. If higher dimensions exist then it is possible for there to be other "parallel" universes.

Io's surface has:

Sulfurous geysers

Io:

Sulfurous volcanoes or geysers 2) A surface with pools of liquid sulfur 3) The most active volcanism in the solar system

Star formation in flocculent spirals is largely from:

Supernova

Which of the following is NOT on the surface of our Moon? Tectonics Maria Highlands Old lava flows Craters

Tectonics

What is the Caloris Basin?

The Caloris Basin is a large impact crater probably from an asteroid.

The most mass a white dwarf can have is

The Chandrasekhar lit of 1.4 solar masses

List one instrument we have built to observe the universe at the following wavelengths and describe what types of objects each is best at studying: Gamma Ray:

The Compton Gamma Ray Observatory (CGRO), or Swift satellite. This studies gamma-ray bursts in the early universe and the most extremely hot objects such as exploding stars and active galaxy nuclei.

List one instrument we have built to observe the universe at the following wavelengths and describe what types of objects each is best at studying: Ultraviolet:

The Extreme Ultraviolet Explorer (EUVE), the Galaxy Evolution Explorer (GALEX) or Hubble Space Telescope. These study hot objects like hot stars and ionized gas clouds.

What is the Great Red Spot and why has it persisted for so many centuries?

The Great Red Spot is a hurricane-like vortex in Jupiter's atmosphere in the southern hemisphere. The winds to the north and south of it blow in opposite directions keeping it spinning. With no subsurface features like mountains to disrupt it, it could persist indefinitely.

Hubble Law (distance)

The Hubble Law says that as galaxies get farther away in space, the speed with which they recede from us increases. So we can measure the amount of recessional velocity and use it to infer distance.

Describe the Kuiper belt and the Oort cloud and the type of objects that are in them.

The Kuiper belt extends from 30 AU to 50 AU from the sun in the plane of the Solar System. It consists of ancient primordial objects made of frozen ices and dust. The Oort cloud is a spherical distribution of the same type of objects extending to a distance of at least extends out to a distance of at least 50,000 AU or about a light year. When these objects fall in toward the sun they become comets.

Explain briefly the efforts we are making to find life on other planets.

The Search for Extra-Terrestrial Intelligence (SETI) conducts ongoing surveillance of radio signals through the frequency band called the "water hole". Their data are searched through a volunteer program called SETI@home that uses individual's computers in place of a screen saver. We are also looking for extrasolar planets through several initiatives like the Kepler and Darwin orbiting telescopes.

List one instrument we have built to observe the universe at the following wavelengths and describe what types of objects each is best at studying: Infrared:

The Spitzer Space Telescope. These study warm objects like brown dwarf stars, star- forming regions, planetary surfaces and interstellar dust.

Explain the Steady State theory of cosmology and how it leads to Olber's paradox

The Steady State theory says that the universe is isotropic, homogeneous, without beginning or end in time and space, and unchanging in time. If the universe is truly homogeneous then every line of sight will eventually end on a galaxy. If it has existed forever then there has been enough time for light from every galaxy we see to reach us. As a result the sky should be ablaze with starlight.

Describe the chromosphere. How did it get its name?

The chromosphere is the 2,000 to 10,000 km thick layer above the photosphere. It glows in the pinkish-red light of H-alpha and so is called the "sphere of color". It is essentially a forest of jets of material shooting upward called spicules.

List one instrument we have built to observe the universe at the following wavelengths and describe what types of objects each is best at studying: Radio:

The Very Large Array in New Mexico or the 105m steerable dish at Green Bank West Virginia, etc. Radio telescopes study cool gas clouds. They can also be ganged together to form high resolution interferometers.

retrograde motion

The apparent backward motion of a planet against the background of stars

ecliptic

The apparent path of the sun through the stars on the celestial sphere.

cosmological principle

The assumption that the universe is isotropic and homogeneous.

Give three reasons why we orbit satellites to observe the universe.

The atmosphere blocks high energy wavelengths, it blurs optical radiation, and it absorbs some radiation at all wavelengths even when it gets through.

critical density

The average amount of matter per cubic meter needed to close the universe.

b) What do we think the dark matter can be?

The best candidates are massive compact halo objects (MACHOS) which would be asteroid sized collections of ice and dust. Or weakly interacting massive particles (WIMPS) which are sub-atomic particles some theories suggest may exist. Neither explanation is very good.

Hot blue giant stars make up less than 1% of the population of all stars. Yet many of the stars we see with our eyes in the night sky are blue giants. Explain why this is the case. Consider the Stephan-Boltzmann law and the inverse square law in your explanation.

The blue giants are so very, very luminous that they can be seen to large distances. Average stars are seen only to much smaller depths. The Stephan-Boltzman law says that if you double the temperature of a star it gives off 16 times more light per square meter. Blue giants are more than twice as hot as average stars like the sun so they are more than 16 times more luminous than them as well if they have the same diameter. But their diameters are also much larger too. By the time their greater temperatures and sizes are accounted for, blue giants can easily be over 10,000 times more luminous than the sun. By the inverse square law, a blue giant that is 10,000 times more luminous than a star like the sun can be seen the square root of 10,000 or 100 times farther than the sun-like star.

Is the dark side of the moon the same as the far side of the moon? Explain your answer.

The dark side is the side facing away from the sun. The far side is the side facing away from Earth. As the moon orbits Earth, the far side is always the same physical side but the dark side is not. The dark half constantly changes with the lunar phases. At new moon, the dark side is the near side and at full moon, the dark side is the far side.

Give two reasons why it is hot during the summer in the northern hemisphere.

The days are longer. The sun's rays are more direct, depositing more energy per square meter than in the winter.

What ultimately happens to the star clusters in the disk of the Milky Way?

The differential rotation of the galaxy disk tears them apart and scatters their stars around the disk. After a few hundred million years they are no longer together in a cluster.

interstellar reddening

The dimming of starlight by intervening dust..

cosmological red shift

The displacement of spectral lines to redder colors caused by the expansion of the universe.

Roche limit

The distance a moon can be from a planet before shattering from tidal forces

focal length

The distance between a lens and its focal plane.

light-year

The distance light travels in one year.(=9.46 x 1012 km).

quarks

The elementary building blocks from which protons and neutrons are formed.

black hole

The end state of a high mass star. An entity for which gravity has completely overwhelmed all other forces of nature.

neutron star

The end state of an intermediate mass star. An entity in which all the electrons have been pushed into the protons.

cosmic singularity

The entity from which the whole universe is postulated to have come from.

density wave

The entity responsible for spiral arms in grand-design spiral galaxies

matter dominated universe

The era when the ratio of matter to energy greatly favored matter.

The event horizon of a black hole is where:

The escape velocity equals the speed of light

CMB

The faint glow of light left over from the Big Bang

Big Crunch

The fate of the universe if it is closed.

chondrite

The first rock-sized bodies that formed in the solar nebula from dust grains.

Cassini division

The gap between Saturn's A and B rings

Enke gap

The gap in the outer portion of Saturn's A ring

planetary nebula

The gas pushed off into space by an evolved low mass star.

celestial sphere

The imaginary sphere centered on Earth that holds the stars.

Planck time

The instant of time after the Big Bang when space and time obtained their characteristics.

There are eight classical planets and at least three dwarf planets, Ceres, Pluto, and Eris, orbiting the sun. In addition, there are hundreds of thousands of

The larger bodies that formed early in the solar nebula that were chemically differentiated.

Wien's law

The law stating that hotter blackbodies look bluer than cooler blackbodies.

Stephen-Boltzman law

The law that says light energy from a blackbody increases as (temperature).

chromosphere

The layer of the sun just above the photosphere

A technique of determining distance that is calibrated by parallax uses a relationship called the inverse-square law. Describe below what this law says and how we use it to determine distance. Draw a diagram if it helps.

The light energy dims as it travels out because it spreads over an increasingly large area that grows as the distance squared. When it is twice as far away, it dims by (1/2)2, or one fourth. When it is 3 times farther away, it dims by (1/3)2 or one ninth, etc.

aurora

The light produced when particles from the sun collide with atmospheric molecules

Hubble law

The linear correlation between the rate of the expansion of the universe and distance.

energy level

The location around an atom where an electron resides.

bulge

The location in the Milky Way where stars orbit like a solid wheel.

turn off point

The location on a star cluster H-R diagram where stars have just left the main sequence. Used to estimate the cluster age

What is Earth's magnetosphere and how does it relate to auroras?

The magnetosphere is the volume surrounding Earth containing particles trapped by its magnetic field. These concentrate in bands called the Van Allen belts. They particles don't stay put, they drift to the northern and southern poles. When the particles strike the upper atmosphere they cause it to glow, creating the auroras.

supercluster

The organization of clusters of galaxies into sheets and strings

Describe 4 discoveries made by Galileo with his telescope. Explain how his observations of Venus proved the Copernican heliocentric cosmology was correct.

The moons of Jupiter Sunspots Lunar craters and mountains Venusian phases and changing angular size Rings of Saturn The Milky Way is made of individual stars Galileo was able to observe Venus going through a full set of phases, something prohibited by the Ptolemaic system which never allowed Venus to be fully lit from the perspective of Earth. This observation essentially ruled out the Ptolemaic system, and was compatible only with the Copernican system.

Chandrasekhar limit

The most mass a white dwarf can have before annihilating in a thermonuclear blast.

What is the Chandrasekhar limit?

The most mass a white dwarf can have. It equals 1.4 solar masses.

plate tectonics

The movement of Earth's crustal plates riding on top of the mantle.

Big Bang

The name for the only seriously considered theory of the universe.

direct motion

The normal eastward movement of a planet against the background of distant stars

meridian

The north-south line passing directly overhead through the zenith.

Describe and contrast the northern lowlands and the southern highlands of Mars. List the prominent features in each.

The northern lowlands are darker in color and have far fewer craters. It is as if an ancient sea or ice field once covered them. The Tharsis rise with its volcanoes extend into them. The southern highlands have a much higher density of craters.

Describe the difference between the maria and the highlands of the moon. In your explanation talk about their age and formation history.

The older lunar highlands first solidified 4.6 billion years ago. However, the smooth lunar mare are relatively recent features. They were formed between 3.1 and 3.8 billion years ago when massive asteroid-size objects collided with the moon and broke through the thin lunar crust. This caused molten lava to flow out from the moon's interior covering the many craters that were on the surface at that time. Because few craters have been formed since then, there are relatively few craters here.

halo

The oldest part of the Milky Way, the structure that formed first.

highlands

The oldest terrain on the moon

radiation dominated universe

The opaque universe that existed for 300,000 years after the Big Bang

Explain the "principle of equivalence" and how it leads to the idea that space-time is curved. Use Einstein's analogy of a man in a rocket and a man in a box suspended on the earth.

The principle of equivalence says that mass defined by inertia and mass defined by gravity are equivalent. Further, it says that everything experienced by the man on the left must be experienced in the exact same way by the man on the right. The man on the right is constantly accelerating. When he sees a light beam go past from left to right, it takes a curved path because he is going faster when it exits his box than he was when it entered. By the principle of equivalence the man on the left, who is not accelerating, must also see light follow the same curved path. The only way for this to be possible is if the space-time near massive objects is curved and the light beam is actually going straight through curved space and time. So gravity is just the manifestation of curved space-time.

self-propagating star formation

The process responsible for creating the arms of flocculent spiral galaxies.

thermonuclear fusion

The process that powers the sun and hydrogen bombs

radiative diffusion

The process, similar to conduction, by which energy moves from the solar core to the convective layer.

celestial equator

The projection of Earth's equator onto the celestial sphere.

The sun gets its energy from fusion through a process termed the proton-proton chain. Describe the proton-proton chain. Draw a diagram if it helps.

The proton-proton chain is a process where 4 hydrogen nuclei (protons) are converted to a single helium nucleus. First two protons combine and one of them immediately decays to a neutron forming deuterium. Another proton combines with the deuterium to form helium-3 and two helium-3 nuclei combine to form helium, ejecting two protons in the process. Gamma rays given off at the first two steps together with an electron-positron annihilation create the energy that ultimately powers the sun.

Olber's paradox

The puzzle of why the sky gets dark at night

Hubble constant

The rate of expansion of the universe

density parameter

The ratio of the actual density of the universe to the critical density

E = mc2

The relationship that describes how matter equates with energy.

era of recombination

The time when the universe cooled sufficiently for atoms to exist

granule

The top of a convective cell as it surfaces in the photosphere.

Explain in a paragraph how the nebular hypothesis accounts for the following: a) why the chemistry of the terrestrial and Jovian planets are different, b) why all planets orbit in the same plane, c) why the planetary orbits are all nearly circular, d) why the planets orbit in the same direction that the sun itself rotates, e) why the solar system ends up with less than half the material that the solar nebula started with and f) why the moon has the pattern of cratering that it does.

The solar nebula collapsed under its own gravity. In the process it began to flatten and spin up until it was a rotating disk of gas. Because if this all planets orbit in the same plane (question b). Conservation of angular momentum amplified the spins and orbital motions concentrating them all in the same direction (question d). The gas and dust within it first concentrated near the center in the protosun. As this heated up, radiation pressure pushed the lighter gases and dust away, leaving the heavier elements near the protosun. In time these swept together to first form planetisimals, then the terrestrial planets. Jupiter and the Jovian planets formed further away, in cooler orbits, where the lighter gases could condense and collect (question a). The same hot protosun pushed much of the solar nebular material back out into space in jets angled at 90 degrees out from the disk (question e) As the planetesimals swept together into protoplanets, their inward and outward motions tended to cancel leaving the protoplanets in mainly round orbits (question c). Since the average size of solar system objects kept increasing but the number of bodies was decreasing as the solar system aged, older surfaces on the moon have more numbers of smaller craters while the younger surfaces have fewer, larger craters (question f).

dark energy

The source of the force that is accelerating the expansion rate of the universe.

What does it mean when an astronomer says that a star "moves" from one place to another on an H-R diagram? What is changing, or moving?

The star does not physically move. It is just changing its surface temperature and absolute magnitude. This is what we mean when we say a star travels on an evolutionary track

b) Where are the fastest moving stars in the galaxy really located and why do they move so rapidly?

The stars at the center of the galaxy nucleus have huge velocities when they whip around the black hole. These are the fastest moving stars in the Milky Way.

thermal equilibrium

The state of having a balance between inflowing and outflowing heat.

hydrostatic equilibrium

The state of having a balance between inward and outward pressures in a gas.

condensation temperature

The temperature at which a substance in the vacuum of space solidifies.

We can also get temperature estimates a different way. Explain how imaging stars through different filters allows us to know their temperatures.

The temperature of a blackbody can be determined exactly by measuring its relative intensity at two different wavelengths. Imaging stars in two different filters and finding the relative intensities in those filters (i.e the B-V color index) is such a measure. So a color index like B-V tells us exactly how hot the surface of a star is. A negative color index means the star is bluer while a positive color index means it is redder.

nebular hypothesis

The theory of how the solar system formed.

No-one has ever seen a single star go through the complete formation process. So how do we understand how stars form? (This was probably not covered in lecture. Just use your own reasoning to hazard a guess)

There are hundreds of billions of stars that we can study. We catch these stars at different times in their lives. By looking at large numbers we can easily infer what each stage in the life of stars of different masses is.

What evidence supporting extrasolar planets has been found in the Orion Nebula?

There are many systems in the Orion nebula that show dusty disks back-lighted by the nebular light.

This drawing shows a black hole.

There is not much to draw! Just a singularity (a) (the point of infinite density) and an event horizon (b) (where the escape velocity equals the speed of light) which is located a distance away called the Schwarzschild radius (c).

In what ways do hydrocarbons on Titan behave like water on Earth?

They are in liquid form and form a "hydrological" system. So it rains hydrocarbons on Titan creating hydrocarbon rivers and lakes.

Which statement about quasars is true?

They are the nuclei of distant galaxies

Write a one or two sentence description of each of these types of spirals:Sa:

They have a large bulge and tightly wound spiral arms. The arms have relatively few HII regions and look smooth.

Write a one or two sentence description of each of these types of spirals:Sb:

They have a medium sized bulge with moderately wound arms. The arms have several HII regions in them and look somewhat lumpy.

Write a one or two sentence description of each of these types of spirals:Sc:

They have small sized bulges and loosely wound, often massive arms. The arms have many HII regions and so look quite lumpy.

Gravity is the force that keeps the planets in their orbits around the sun. It also keeps the moon and spacecraft in their orbits around Earth. Astronauts in an orbiting spacecraft have not escaped Earth's gravity, so they have weight, yet we refer to them as being "weightless". Why do they appear as if they have no weight?

They have weight and are falling toward Earth. However, they are also traveling rapidly in a perpendicular direction. This velocity carries them eternally beyond the horizon as they fall downward. The result is that they "fall" in a circle without getting any closer to Earth. Since the capsule or shuttle is falling at the same rate, they appear weightless with respect to it.

Type Ia supernovae (distance)

Type Ia supernova all reach the same peak absolute magnitude when they explode. Careful observations of these supernovae in nearby galaxies whose distances are known from Cepheid variable stars has taught us what this peak brightness is. We measure the apparent peak brightness, obtain a distance modulus and calculate the distance. Since these supernovae are so bright they can be seen half-way across the universe, we use them to find distances up to 5-6 billion light years away.

Describe how a type Ia supernova explosion takes place. (Note that these types of supernovae are all similar in their makeup and evolution, so we believe that their absolute magnitudes are all the same.

Type Ia supernova are white dwarfs with evolving red giant companions. As the red giant expands, it overfills its Roche limit and material spills over onto the white dwarf. If the mass of the white dwarf is increased beyond the Chandrasekhar limit, the gravitational pressure on it will cause the carbon in the interior of the white dwarf to ignite in a runaway fusion reaction that blows the star to bits.

This drawing shows the moon orbiting Earth. Identify the a) new moon; b) 1st quarter moon; c) full moon; and d) 3rd quarter moon.

USE DIAGRAM

Describe how we map spiral arm structure of the Milky Way disk. What is it like and where is the sun located?

Using HR diagrams we find distances to OB stars and HII regions since the arms are sites of star formation and OB stars live and die at the location of their births. We find that the Milky Way has four arms. The sun is on a small "spur" apart from the major arms.

The very smallest parallax angle we can measure is about 0.001 arcseconds. What distance does this correspond to?

Using d[pc]=1/p, where p=.001, the greatest distance that can be resolved using parallax is 1000 pc.

Compare and contrast the tectonics of Venus, Earth, and Mars. Explain why it is different on each planet. In the process, explain why volcanoes on Mars are so large, volcanoes on Venus are so flat, and volcanoes on Earth are clustered only in specific locations:

Venus: Venus has a "light- flaky" crust. It is more pliable that the crusts of Earth and Mars. Convective currents in Venus' interior do not break it into plates like on Earth but rather cause it to wrinkle and bunch up at specific locations Uniform cratering suggests that the surface is not remade like Earth's but is all the same age giving more evidence that there are not moving plates like on Earth. Volcanoes on Venus are flat because the lave flows easily and the huge atmospheric pressure pushes down hard on them. Mars: Mars has a "thick rigid" crust. Plate tectonics stopped a long time ago on Mars since with its smaller size it cooled faster than Earth or Venus. But it still had convective "hot spots" that created volcanoes like we see on Earth. On Earth, plate tectonics limits growth by moving the crust over the hot spots creating new volcanoes and extincting older ones. On Mars volcanoes like Olympus Mons erupted in one place for billions of years making them very large. While Mars does not have plate tectonics, it still has had interior motions that pushed the Tharsis rise upward and fractured the crust creating the Valles Marinaris formation. Earth: Earth's crust is just the right thickness to split into plates and raft about on the surface. The plates are stiff enough to split into hard sections that maintain their general form when they collide. With few exceptions volcanoes form only on the boundaries between the plates or along places where collisions and drifting have weakened the plates as in Utah and east Africa

Cepheid variables (distance)

We can infer the absolute magnitude of pulsating variable stars by measuring their pulsation periods. The longer the pulsations, the greater their luminosities. We then again measure their apparent magnitudes, compare it with their absolute magnitudes and calculate their distance. Since Cepheid variable stars are very bright, this method can obtain distances to the nearest 3 or 4 dozen galaxies.

If proto stars are embedded in dusty dark nebula cocoons, how do we know anything about them?

We detect them through infrared imaging. Infrared light can penetrate through the dust revealing the protostar inside.

Is space infinitely large?

We don't know. It might be but does not have to be.

Explain why Saturn's rings seem to disappear every 15 years. Draw a picture if it helps.

We see Saturn's rings edge on here and here, while we see them closer to face-on in the other two locations. When they are seen edge on, they seem to disappear because they are so thin.

Let your imagination go wild and speculate on how the Milky Way would appear to us if the sun were relocated to far out in the halo above the disk:

We would see the disk of the Milky Way filling the night time sky half of the year. Since the halo has no dust and hence no interstellar extinction, the bulge and disk would be very bright and dominate the night-time sky. It would look spectacular. The other half of the sky would be rather dark and relatively devoid of stars since the halo stars are old, dim, red, and sparse. Perhaps there might be a globular cluster or two close enough to look interesting.

coronal loop:

Well shaped loops that trace the magnetic field as it erupts from a sunspot area and arches over to an adjacent area. They glow in the light of gas that is raining out of the corona and falling down along these field lines onto the photosphere.

List one instrument we have built to observe the universe at the following wavelengths and describe what types of objects each is best at studying: X-ray:

XMM-Newton or Chandra. These study very hot objects like accreting black holes, exploding stars and their remnants, and active galactic nuclei.

Does water of any type exist on Mars today? If so, where?

Yes. It is frozen in the polar ice caps and frozen as permafrost in the soil at the poles and mid- latitudes.

A process on Venus termed the____ traps radiation inside the atmosphere and has driven the surface temperature up to ____ degrees Fahrenheit.

__greenhouse______ _effect___ ___900___

Meteors on the ground are called

__meteorites_.

Because Venus spins with_______rotation, the sun rises in the ____ on Venus and takes 58.4 days before it sets

__retrograde_____, __west____

Venus is one of the brightest objects in the sky. The reason for this is that it is close to both Earth and sun and because a thick layer of clouds reflect 76% of all the light it receives. These clouds are made of _____making Venus a very inhospitable place.

__sulfuric_______ _acid____

The Milky Way is a member of a cluster called _____ which is a small ___ cluster of about 30 galaxies.

__the Local Group__, _poor____

The terrestrial planets contain heavier elements such as

_iron_,_silicon_,_magnesium,_sulfur,_nickel, oxygen.

Describe the two ways that we search for extrasolar planets.

a) We look for eclipses when planets transit across the face of a star, blocking its light just a little bit. b) We look for Doppler shift "wiggles" in the radial motion of star as the planet orbits around it.

In all galaxies with spiral arms, arcs of increased mass concentration called This causes

density waves; they slow stars and gas down as they orbit through a gravitational compression of interstellar clouds of gas, ices, and dust which collapse and form stars.

In the Sc galaxies, which are also called fleecy or ___, star formation and destruction is so rapid that supernova explosions are mainly responsible for compressing the gas and creating new stars. This process is called

flocculent spirals self-propagating star formation

Galaxies are not scattered randomly across the sky but are grouped into clusters. These are classified as ___ if they have dense, crowded cores or _____ if they have few members and a looser organization.

rich and poor

A ________ day is defined as being the interval between times when a star is directly overhead and is about 23 hours 56 minutes. This means that if a star crosses the meridian at 8:00 PM one night, the next night it will cross the meridian at _____.

sidereal 7:56

Photons travel outward from the core through

the ______radiative____________ zone bya process called __radiative diffusion_____. From here, super heated cells of gas rise upward through the ___convective____ zone. At the top of this zone the cells radiate their energy into space, cool, and fall downward again.

A moon that is new and getting more illuminated every night, is in the ____________ portion of its cycle. When we see exactly half illuminated it is a ___________ moon. After this it enters the _______________ portion until the entire face is illuminated at the _____________ phase. As it begins to decrease in illumination, it is in the __________ portion until it is again half illuminated as a _____________ moon. It continues to decrease in illumination as a _______________ moon until it arrives again at the new moon phase.

waxing crescent first quarter waxing gibbous full moon waning gibbous third quarter waning crescent

Magnitudes are a logarithmic expression of brightness. A magnitude difference of 1 means that the brightness ratio is a factor of 2.512. A magnitude difference of 2 means that the brightness difference is 2.512 x 2.512 = (2.512)2 = 6.3. A magnitude difference of 5 is (2.512)5 which is exactly 100. With this as a guide how much brighter is: Sirius (m~-1) than the naked eye limit (m~6)?

Δm = 7; (2.512)7 = 630

The 111111 coordinate is divided into degrees, minutes, and seconds. Its zero line is the 222222. The greatest value it can have is plus or minus 33333 degrees.

1 declination 2 celestial equator 3 90

A 1111111 eclipse occurs when the moon passes into Earth's shadow. This can be either a 22222 eclipse if the moon is not completely within the umbra of Earth's shadow or a 33333 eclipse, if it is entirely obscured. These eclipses only occur when the moon is at the 4444 phase. Similarly, a 5555 eclipse occurs when Earth passes into the moon's shadow. These eclipses are called 6666 at places on Earth that are inside the umbra of the shadow, 7777 at places that are inside the penumbra of the shadow and 8888 if the shadow umbra doesn't touch the surface of Earth at all. These eclipses only occur when the moon is at the 9999 phase. The 10101010 of 11111111 , which is the intersection of the plane of the moon's orbit with the plane of Earth's orbit, must be pointing at the sun for an eclipse to occur. The yearly path that the sun traces on the celestial sphere is called the 12121212 because this is the only place where eclipses can occur.

1 lunar 2 partial 3 total 4 full 5 solar 6 total 7 partial 8 annular 9 new 10 line 11 nodes 12 ecliptic

The 11111111 coordinate is divided into hours, minutes, and seconds. Its zero point is the Vernal Equinox. The greatest value it can have is 2222222 hours.

1 right ascension 2 24

The sky is mapped out by a grid of two coordinates called 11111 and 222222.

1 right ascension 2 declination

Explain what a Doppler shift is and how it affects light from a galaxy that is a) going away from us, b) coming toward us and c) moving rapidly past us across the sky but not coming closer or farther. Draw a picture if it helps.

A Doppler shift is the stretching or compression of wavelength when the emitting or receiving sources are moving either toward or away from each other. a) moving away causes the colors to become redder. b) moving toward causes the colors to become bluer. c) moving across the sky does not affect the wavelengths. So Doppler shifting only tells us motion toward or away from us.

resolving power

A measure of the ability of a telescope to see fine detail.

Why is a total eclipse of the sun visible only from certain parts of Earth?

A total eclipse is where the umbra of the moon's shadow touches Earth's surface. It only touches specific places and not the entire surface, so total eclipses are visible only at those locations.

acceleration

Any change in the speed or direction of an object's motion

There are 88 constellations in the sky. We categorize them by the season in which they are visible after sunset with circumpolar stars being those that are always above the horizon. a) Why did the ancient people divide the sky into constellations? b) Why do modern astronomers continue to use them?

Constellations were originally a means of preserving knowledge and legends that were passed down from generation to generation among people who did not necessarily know how to read or write. We use them today to divide the sky into sectors like the states divide up the USA or like counties divide up a state.

Explain how individual atoms create both emission and absorption line spectra.

Emission line spectra arise from electrons falling from higher to lower levels in atoms of low density gasses. They jump to the high levels from either collisions caused by heating or by absorbing light from a continuous spectrum. When they absorb light, it is at the same energy and hence the same wavelength, as the energy emitted when the electron fell down. But since absorption removes energy from the spectrum it creates an absorption line.

Define and explain the relationship between a) frequency, b) wavelength, c) speed, and d) energy.

Frequency (f) is the number of waves that pass a point per second. Wavelength (λ) is the spatial extent of a wave. Speed is frequency times wavelength and has a constant value for all electromagnetic radiation traveling in a vacuum. This means that as frequency increases, wavelength must decrease. Energy is proportional to frequency. So photons of gamma rays have much more energy than photons of radio waves.

semimajor axis

Half of the longest diameter across an ellipse.

Light with all of its colors is part of a family of radiant energy called electromagnetic radiation. List below the types of this energy, ordered from longest wavelength to shortest wavelength. Be sure to include light.

LONGEST-SHORTEST: Radio, Microwave, Infrared,_Visible Light, Ultraviolet Light, X-ray, Gamma-ray Roman Men Invented Very Unusual X ray Guns

Now describe how the sun relates to the Arctic and Antarctic circles.

Now describe how the sun relates to the Arctic and Antarctic circles.

This drawing shows Earth in its orbit around the sun. Identify the times of the a) summer solstice; b) winter solstice; c) autumnal equinox; and d) vernal equinox for a person living in the northern hemisphere.

PRACTICE WITH DIAGRAM

This drawing shows Earth inside the celestial sphere. Draw in the celestial equator, the north celestial pole, the south celestial pole, and the ecliptic. Then label the location of the sun at the time of the a) summer solstice; b) winter solstice; c) autumnal equinox; and d) vernal equinox.

PRACTICE WITH DIAGRAM

What is precession and how does it affect a) the north star, b) when the constellations are visible?

Precession is the slow, regular "wobble" of Earth's axis with respect to the stars. a) It causes the north celestial pole to change position, going in a circle with a period of 26,000 yrs. b) Because the pointing direction of Earth's rotation axis changes, in 13,000 years the northern hemisphere will tilt toward the sun when Earth is on the opposite side of its orbit from where it is now in summer. Calendars are adjusted to keep the seasons on the same days of the years as they are now. So in 13,000 years summer will still be in July and winter in January. However the night- time constellations will change and in 13,000 years the current winter constellations will appear in July and the current summer constellations will appear in January.

If you lived on the moon would you see Earth rise and set, or would it stay in the same place? Explain your answer

Since the moon is in synchronous orbit with Earth and keeps one face always pointed toward it, you would always see Earth in the same place in the sky.

Explain how the Vernal Equinox can be both a time of the year and a place in the sky.

The Vernal Equinox is the location in the sky where the sun crosses the celestial equator going north. Really, it is when Earth is at the place in its orbit so that the sun appears to be exactly on the celestial equator in spring. It does so on March 21 so we refer to both the time and the place as the Vernal Equinox.

astronomical unit

The average distance between Earth and the sun (=1.5 x 108 km).

umbra

The shadow area behind Earth or moon where the sun is completely obscured.

penumbra

The shadow area behind Earth or moon where the sun is partially obscured.

precession

The slow wobble of Earth on its rotation axis.

Suppose you go outside after sunset and see the stars. You then arise before sunrise and see the stars again. How have they shifted and why?

The stars have all rotated to the west. The western-most stars have set and new ones have risen in the east. This is because Earth spins on its axis.

At the summer solstice, the sun is at the highest possible point in the north with a declination of 23.5° north of the celestial equator. At the winter solstice, the declination of the sun is -23.5° which is south of the celestial equator. At the time of the autumnal and vernal equinoxes the declination of the sun will be 0° which is on the celestial equator or in other words directly over Earth's equator. The tropical zone on Earth is defined as being the band around the equator between ± 23.5°. What is unique about the sun inside that zone?

The sun is seen at the zenith only at points inside this zone.

synchronous rotation

When one side of a body always faces the planet it revolves around

total eclipse

When the moon entirely blocks the sun.

summer solstice

When the sun is farthest north of the celestial equator (about June 22)

winter solstice

When the sun is farthest south of the celestial equator (about December 22).

autumnal equinox

When the sun moves from north to south across the celestial equator (about September 23).

vernal equinox

When the sun moves from south to north across the celestial equator (about March 21).

Proxima Centauri is 4.22 light-years away. The sun is 8 light minutes away. Proxima Centauri is then ________ times farther away than the sun.

about 277,000