Astronomy final
The solar cycle (sunspot cycle)
11 years Solar Minimum-# of sunspots are low indicating low solar activity Solar Maximum - A period of time where the sunspots are high The solar cycle - 2 years (hail cycle Every 11 years the suns's poles flip - north becomes south becomes north. Every 22 yrs the poles return to the position where they started the cycle. this flip is due to the movement of the magnetic fields inside the sun that are constantly moving
The age of the universe is estimated to be how old?
14 billion years old
The presently accepted value of the Hubble constant gives an age of what?
14 billion yrs.
Stellar Luminosity classes
1a-Bright Supergiants 1b-supergiants II-Bright Gians III-giants IV-Subgiants V-Main Sequence stars and dwarfs
From a distance of 1 ps, the angular size of Earth's orbit would be:
2 arc seconds
A collapsing cloud fragment that will form a star of one solar mass (like our Sun) has a mass of about
2 solar masses
what is the typical main sequence lifetime of a b-type star?
20 million years
Hipparcos observations have given us good data on stars to about how many parsecs?
200 parsecs
As a radio source, the period of "pulsar Earth" is:
23 hrs. 56 min.
In the critical universe now proposed, the ration of matter/energy is about: (Ch.26)
27:73.
At the distance of Jupiter (6 times further away from the sun than Earth) the amount of sunlight received per square cm differ by what factor
36 times less
According to the data from the microwave background radiation, at what speed and in what direction is Earth moving through the Universe? (Ch. 26)
380 km/s in the direction of Leo
Fossil record of early life-forms on Earth suggest that life began about:
4.6 billion years ago
A nearby star has a parallax of 0.2 arc second. What is it's distance? (ch. 17)
5 parsecs
What temperature of the layer of gas that produces the visible light of the Sun is
5,800 K
the temp of the layer of gas that produces visible light of the Sun is:
5,800 K
Our Sun, along with most of the stars in our neighborhood probably formed about:
50 million years
the quasars with the largest presently known redshifts are
6.
What makes Cygnux x-1 a good black-hole candidate?
- visible companion is 25x the mass of the sun - Cynus x-1 is thought to have a mass around 10x that of the sun - detailed studies suggest hot gas is flowing out of he bright star towards an unseen companion - X-ray radiation emitted from immediate neighbourhood implies presence of very high temp gas - size of X-ray emitting region of Cygnus x-1 must be very small These properties suggest that the x- ray emitting companion could be a black hole. What makes Cungus X-1 a good black hole
If a star is found by spectroscopic observations to be about 500 parsecs distance, what is its stellar parallax?
.002"
Procyon lies about 13 light years light distance, thus its parallax is about:
0.25"
The simplest life forms appeared on Earth when it was how old? (Ch. 28)
1 billion years old
Things that are attracted by gravity:
1) Any object with mass 2) electromagnetic radiation 3) antimatter 4) neutrinos
What evidence is there that supernovae really have occured
1) Crab Nebula 2) observations of actual explosions 3) supernova remnants 4) existence of heavy radioactive elements in nature
When an interstellar cloud fragment shrinks:
1) Density rises 2)Temp rises 3)It first becomes opaque 4)Pressure rises
What made supernova 1987a so useful to study?
1) In the large Magellanic Cloud we already knew its distance 2) Its progenitor had been observed previously 3) It occurred after new telescopes, such as Hubble, could observe it very closely 4) We saw direct evidence of nickel to iron decay in its light curve
Star Temperatures
1) Surface temp = apparent brightness 2) Match the bodies to the appropriate blackbody curve astronomers can estimate a star's temp simply by measuring and comparing the amt. of light received through different colored filtered. This is known as photomotry. The brighter the star, the hotter it is.
What direct evident do astronomers have that supports the heavy element formation in the stars
1) light curves of type-I supernova 2) the presence of technetium in giant star spectra 3) observed elemental abundances 4) gamma-ray emissions from decay of cobalt 56 in supernovae
If a star has a stellar parallax of 0.05", then its distance in light year is what?
65 light years.
The Chandrasekhar mass limit is
8 solar masses
A cloud fragment too small to collapse into a main sequence star becomes what?
A brown dwarf
A cloud fragment too small to form becomes
A brown dwarf
T Tauri object
A class of variable stars named after their prototype - they are found near molecular clouds and are identified by their optical variability and strong chromospheric lines.
What is the H-R Diagram?
A color-magnitude diagram where about 90% of all stars that lie on the main sequence are plotted.
Explain two ways that a star's real motion in through space translate into motion that is observable from Earth?
1) radial velocity - along the line of sight-can be measured using the Doppler effect. 2) transverse velocity - perpendicular to our line of sight (this is used for nearby stars)
How is a star's stellar radii measured?
1)Measure the star's surface temp 2)Measure the star's luminosity R=square root of luminosity / Temp squared
how are distances measured by spectroscopic parallax?
1)The star's apparent brightness and spectral type are measured without knowing how far away it is 2) Use the spectral type to estimate the star's luminosity 3)apply the inverse square law
For a white dwarf to explode entirely as a Type I Supernova, its mass must be
1.4 solar masses, the Chandrasekhar Limit.
For a white dwarf to explode entirely as a Type I supernova, its mass must be
1.4 solar masses, the Chandrasekhar limit.
what is the typical main sequence lifetime of a G-type star?
10 billion years
How long does it take for a star like the Sun to evolve from the main sequence to the top of the red-giant branch?
100 million years
According to our definition, we have been a technological civilization for how long?
100 years
How long have we been a technological civilization?
100 years
The supernova that form M-1, the Crab Nebula, was observed in
1054 AD by Chinese and other oriental and mid eastern astronomers
The absolute magnitude of a star is its brightness as seen from a distance of: (Ch. 17)
10pc
How would Earth appear at radio wavelengths to extraterrestrial astronomers?
A distant observer would detect blasts of radio radiation from Earth as our planet rotates every day
Stars form from a collapsing cloud that fragments into smaller and smaller pieces. This process takes how long?
A few million years
the stars formed in nebulae like the Orion nebula probably formed how long ago? (Ch. 19)
A few million years ago
Prominence
A loop of gas following the magnetic field lines between sunspots pole
What is a star?
A luminous ball of gas, mostly hydrogen and helium. It is held together by its own gravity. Nuclear fusion reactions in its core support the star against gravity and produce photons and heat as well as small amounts of heavier elements. Stars form when an interstellar cloud collapses under its own weight and breaks up into pieces comparable in mass to our Sun.
cosmological constant
A possible candidate for the nature of dark energy
Black hole
A region of space from which nothing can escape.
Star-Cluster
A single collapsing and fragmenting cloud which can give rise to hundreds or thousands of stars
If a newly formed start has an excess of heat, then it will likely have what?
A slower contraction rate
Olber's paradox
A thought experiment suggesting that if the universe were homogenous, infinite, and unchanging, the entire night sky would be as bright as the surface of the sun.
How can a white dwarf dramatically increase in brightness?
A white dwarf can dramatically increase in brightness only if it (a) has another star nearby; (b) can avoid nuclear fusion in its core; (c) is spinning very rapidly; (d) is descended from a very massive star. ... (b) A star having the same mass as the Sun. (e) A star that is twice as massive as the Sun.
How can we tell whether a star cluster is young or old?
A young star cluster will be surrounded by emission nebulae and stars will be hotter. An old star cluster will be located in the halo, will have much larger, cooler stars that aren't along the main sequence.
White Dwarfs
A&f type stars (lower left) Also called degenerate dwarf. Has a stellar core remnant composed mostly or electon-degenerate matter. It is very dense, its mass is comparable to that of the Sun while its volume is comparable to that of the Earth. It is essentially what stars like the Sun become after they have exhausted their nuclear fuel. Near the end of its nuclear burning state, this type of star expels most of its outer material creating a planetary nebula. Only the hot core of the star remains.
What does a large number of sunspots reveal
Above average number of flares and prominences
What is the leading model for the central engine of an active galaxy?
Active Galactic Nucleus
The cosmic background radiation is observed from what?
All directions equally
Luminosity class
Allows astronomers to distinguish main-sequence stars from giants and supergiants of the same spectral type
What important molecules of life did Miller and Urey brew up?
Amino Acids
accretion disk - how does it form
An accretion disk is a structure (often a circumstellar disk) formed by diffused material in orbital motion around a massive central body. The central body is typically a star. Friction causes orbiting material in the disk to spiral inward towards the central body.
Flares
Another type of solar activity observed low in the sun's atmosphere near active regions. They are the result of magnetic instabilities. More violent than prominences. X-Ray and ultraviolet emissions are especially intense in the extremely compact hearts if flares where temps can reach 100m kelvin
Stellar Luminosity is measured in two ways:
Apparent magnitude - how bright the stars appear from Earth how bright the star appears at a distance of 32.6 light years
According to the parameters derived for the Drake Equation, where should astronomers look for life in the MWG?
Around O,B, or A stars that are in single star systems located in the galactic habitable zone with a multiple planet system with jovian outer planets and at least one terrestrial planet within the star's habitable zone
How do the late evolutionary stages of high-mass stars differ from those of low mass stars?
As a result of helium fusion, low mass stars eventually form a carbon core that collapses but cannot collapse enough to attain a high enough temperature to allow the fusion of carbon. The outer part of the star continues to expand and as the final shells of hydrogen and helium fusion die out, this outer part of the star is ejected into space. This cloud of gas is known as a planetary nebula. The core of the star remains, continues to cool, and is known as a white dwarf. In contrast, more massive stars are able to reach the core temperatures required for more complex nuclear fusion processes: the fusion of carbon, oxygen, and heavier elements. As the fusion processes get more complex, they take less and less time. The most massive stars can fuse elements to create iron cores, and shortly thereafter they explode.
When does a massive star become a supernova?
As the star runs out of nuclear fuel, some of its mass flows into its core. Eventually, the core is so heavy that it cannot withstand its own gravitational force. The core collapses, which results in the giant explosion of a supernova. The sun is a single star, but it does not have enough mass to become a supernova
Cosmological redshift
Associated with Hubble expansion
What evidence is there for black holes much more massive than the Sun
Astronomers have found that stars and gas near the centres of many galaxies are moving extremely rapidly, orbiting some very massive unseen object. Masses inferred from Newton's laws range from millions to billions of times the mass of the sun. The intense energy emission from the centres of these galaxies and the short timescale fluctuations in that emission suggest the presence of massive, compact objects.
At what evolutionary stages must astronomers use readio and infrared radiation to study prestellar objects? Why can't they use visible light?
At stages 1 and 2, radio emission from interstellar molecules within the interstellar clouds are examined.
What evidence do we have that there no structure in the universe on very large large scales?
Based on galaxy surveys and pencil beam surveys, we know that the universe is both homogeneous and isotropic. 300 mpc is the larger scale, there is no known structure larger
Pulsar
Beams of electromagnetic energy that can we see on Earth
as a star evolves, why do heavier elements tend to form by helium capture rather than by fusion of like nuclei?
Because helium capture is much more common than fusion.
Why does the H-R diagram constructed from data on the brightest stars differ from the diagram constructed from data on the nearest stars?
Because of their luminosity, we can see them more easily. Just because a star is close, does not not mean it is necessarily bright.
According to the inverse square law - if the distance to a lightbulb increased by a factor of 5, the bulb's apparent brightness would be:
Becomes 25 times less
This is TRUE about the ages and masses of spiral and elliptical galaxies:
Both types are about the same age, but spirals vary less in mass
this is NOT true about the ages and masses of spiral and elliptical galaxies
Both types are about the same age, but spirals vary less in mass.
Prestellar objects in which nuclear fusion never starts is referred to as
Brown Dwarfs
How does the Sun generate energy?
By converting hydrogen into helium in its core by the process of nuclear fusion. Nuclei are held together by the strong nuclear force. When four protons are converted to a helium nucleus in the proton-proton chain, some mass is lost. The law of conservation of mass and energy requires that this mass appear as energy, eventually resulting in the light we see. Very high temps are needed for fusion to occur.
How is the Tully Fischer relation used to measure distances to galaxies?
By measuring the amount of broadening in emission lines, we can determine a galaxy's rotation. Once we know the rotation, we can determine luminosity. Comparing a galaxy's luminosity with its apparent brightness gives us its distance.
How can stellar masses be determined by observing binary-star systems?
By measuring the distance from each star to the center of mass of a visual binary yields the ratio of stellar masses
how are where are nuclei heavier than iron formed?
By neutron capture, whereby heavier nuclei are formed by the absorption of neutrons. Deep in the interiors of highly evolved stars, conditions are ripe for neutrons to occur... adding neutrons doesn't change an element, however, a more massive isotope of the same element is produced.
This technological advances would make it harder for extraterrestrial life to find us?
Cable TV
Organic molecules are:
Carbon based
Why does the Cepheid "standard candle" have limited usefulness beyond 20 Mpc?
Cepheids are too faint to be seen beyond that distance, even with HST
Living Organisms:
Characterized by their ability to react to their environment, to grow by taking in nutrition from their surrounding, and to reproduce, passing along some of their own characteristics to their offspring.
In what model will the universe stop expanding?
Closed Universe
Hubble's constant
Constant of proportionality - value thought to be around 70 km/s/Mpc. Astronomers use this law to determine distances to the most remove objects in the universe.
Compare to other stars on the H-R diagram, red giant stars are so named because they are -
Cooler
Standard Solar Model
Created because scientist lack direct measurements in order to understand the conditions in the interior of the sun. They constructed mathematical models of the sun consisting of all available data and combining it with solar physics theories. This structure provides the closest possible results.
Necessary to explain galaxy rotation and gravitational interactions
Dark Matter
In comparing first magnitude Deneb with second magnitude Polaris, what do we find?
Deneb appears 2.5 times brighter to us than does Polaris.
Why are neutrino detectors important to the study of supernovae?
Despite some unresolved details in SN 1987A's behavior, detection of this neutrino pulse is considered to be a brilliant confirmation of theory. This singular event—the detection of neutrinos—may well herald a new age of astronomy. For the first time, astronomers have received information from beyond the solar system by radiation outside the electromagnetic spectrum.
A typical open closer will dissolve in about the same amount of time as the time since what?
Dinosaurs walked the earth
energy transport
Due to the intense heat in the sun, protons and neutrons move very rapidly and when they collide due to magnetism ,they create even more energy. Thus E=MC2 or energy = mass *speed of light.
A spherical galaxy, like M87, which looks like a monster global cluster, is type
E0
The flattest of the ellipticals are type
E7
If the sun were magically to turn into a black hole of the same mass
Earth's orbit would remain unchanged
A white dwarf is supported by the pressure of tightly packed-
Electrons
chemical evolution
Gases emanating from fissures, and geysers produced an atmosphere rich in hydrogen, nitrogen, and carbon compounds and poor in free oxygen. As Earth cooled, ammonia, methane, carbon dioxide, and water formed. The state was set for the appearance of life.
The observed slowing of a clock in the vicinity of a black hole is a prediction of what?
General relativity.
why don't stars on the main sequence explode?
Gravity
What is the relationship between the average lifetime of galactic civilizations and the possibility of our someday communicating with them
Has a catastrophic event already ended that civilization
helium flash
Helium burns violently - the flash expands the score and reduces the star's luminosity
Solar Spectra
Helps scientists understand and identify the elements in the sun (67). The emission and absorption lines are created by the amount of energy in the photons. A photon will jump to the next atom based on the amount of energy that it has. this energy comes from the elements - the less elements in the photon, the less energy it has.
During stage 3 of star formation, the dense, opaque region at the center of the sun is called what?
Herbig Haro object
Which Greek astronomers compiled the first catalog of stars, accurately measured their positions, and defined the basic system of stellar brightness?
Hipparchus
coronal holes
Holes in which wind escapes. Deficient in matter b/c they gas where there is able to stream freely in to space at high speeds, driven by disturbances in the sun's atmosphere and magnetic fields. the largest holes can be hundreds of km across and may survive for many months.
primevil fireball
Hot, dense state at very early times, just after the Big Bang. According to Hubble's Law, 14 billion years ago all the galaxies in the universe lay on top of each other. Then, the universe began to expand at a rapid rate, and its density and temperature fell rapidly as the volume increased.
After the core of a Sun like star starts to fuse helium on the horizontal branch, the core becomes -
Hotter
Evolutionary Track
How stars move in the H-R diagram
radius-luminosity-temperature relationship
How the sizes of most stars are estimated.
What is the role of language in cultural evolution?
Human intelligence is language. it allowed individuals to signal one another while hunting for food or seeking protection. Also, our ancestors could share ideas as well as food and shelter.
How do we know that the energy-emitting regions of many active galaxies must be very small?
If an object's luminosity fluctuates rapidly, then it must be compact; an object cannot 'flicker' in less time than radiation takes to cross it.
light curve
In astronomy, a light curve is a graph of light intensity of a celestial object or region, as a function of time. The light is usually in a particular frequency interval or band.
Most stars in the Milkyway probably formed
In clusters in the galaxy's spiral arms
In what sense are the quasars "quasi-stellar"?
In short time exposures, their images looked stellar.
Region: Solar wind
Inner Radius: 10,000,000 Temp: 1,000,000 Density: 10-23 Defining Properties: Solar material escapes into space & flows outward through the solar system
Region: radiation zone
Inner Radius: 200 km Temp: 7,000k Density: 15,000 Defining Properties: Energy transported by electromagnetic radiation
Region: Convection Zone
Inner Radius: 496km Temp: 2,000,000k Density: 150 Defining Properties: Energy carried by convection
Region: Chromosphere
Inner Radius: 696.5km Temp: 4,500k Density: 5*10-6 Defining Properties: Cool Lower atmosphere
Region: Photosphere (solar surface)
Inner Radius: 696km Temp: 5,800k Density: 2x10 -4 Defining Properties: Electromagnetic radiation can escape the part of the sun we can see
Region: Transition Zone
Inner Radius: 698km Temp: 8.000k Density: 2*10-10 Defining Properties: Rapid increase in temp
Region: Corona
Inner Radius: 706km Temp: 3,000,000k Density: 10-12 Defining Properties: Hot low-density upper atmosphere
Region: core
Inner radius: 0 Temp (k): 15,000,000 Density: 150,000 Defining properties: Energy generated by nuclear fusion
An iron core cannot support its star because
Iron cannot fuse with other nuclei to produce energy
the Large and Small Magellanic Cloud fall into Hubble's class
Irr I
The concept that the direction of the observation does not matter overall is what? (Ch. 26)
Isotropy
What unusual discovery was made about the Murichson Meteorite?
It contains amino acids
This statement about the Local Group is FALSE:
It contains the large radio galaxy Centaurus A.
What are the advantages in using radio waves for communication over interstellar distances?
It is cheaper and much more practical alternative to direct contact
Proper Motion
It is the annual apparent motion of a star across the sky.
During a protostar's T Tauri phase:
It may develop very strong winds
How does the cosmological redshift relate to the expansion of the universe?
It occurs as a photon's wavelength is 'stretched' by cosmic expansion. The extent of the observed redshift is a direct measure of the expansion of the universe since the photon was emitted.
Radio telescopes cannot simply scan the skies looking for signals because:
It would be far too expensive and inefficient.
The density of the Sun is most similar to which object
Jupiter
The density of the Sun is most similar to which object?
Jupiter
Where-besides Earth and the planet Mars-might we hope to find signs of life in our solar system
Jupiter's Moons - Europa and Ganymede Saturn's Moons - Titan and Enceladus
Red Giants
Large, cool, and luminous
describe the contents of the local Group. How much space does it occupy compared to the volume of the Milky Way
Made up of nearly 50 galaxies within approx. 1 Mpc of our Milky Way Galaxy. Only a few are spirals, most are dwarf elliptical or irregular galaxies. - Milky Way and Andromeda are largest members - Most other galaxies are gravitationally bound to them
Luminosity classes
Main Sequence:V Subgiant:IV Bright Supergiant: Ia White Dwarfs: VII Giants:III
The famed meteorite with carbonate rocks and possible microfossils came from
Mars
The gravitational contraction of an interstellar cloud is likely primarily the result of its what?
Mass
What is the single most determinant of a how a star will evolve
Mass
What ultimately determines a star's position on the main sequence?
Mass
Local Group
Milky Way, Andromeda, and several other smaller galaxies that form a small gravitationally bound collection of galaxies
Active sun
Most frequent and violent are the time of solar max, the photosphere surrounding a pair of group of sunspots can sometimes erupt explosively, spewing forth large quantities of energy particals in the corona. In these active regions, we can see the solar prominences which are sheets of glowing gas ejected from these regions on the solar surface moving through the inner parts of the corona under the influence of the sun's magnetic field. As a result of magnetic instabilities, are solar flares which also take place in the active regions.
Neutrinos
Most of the energy of the supernova is carried outward via a flood of neutrinos
this statement about starbirth is false?
Nuclear reactions begin in the core by state 4
Blue Giants
O&B type stars (upper left)
Methods for star classification
O, B, A, F, G, K, and M 0-9 (0 being the hottest and 9 being the coolest)
Spectral classes (types) and classifications (p.432)
OBAFGKM - The letter represents the amount of hydrogen absorption lines. 0-9 - the lower the number the hotter the star examples: our Sun (G2), Vega (A0), Barnard's star (M5), Betelguese (M2)
Carbon
Of all the chemical elements, this is the most crucial to the complexity of life
What are characteristics of globular cluster stars?
Old age and hundreds of thousand to millions of members of stars
Coronal Mass ejection
Sometimes associated with flares and prominences. Giant magnetic bubbles of ionized gas that separate from the rest of the solar atmosphere and escape into interplanetary space. Occur once p/wk during times of sunspot min but up to 2 or 3 times p/day @ solar max. Carry enormous amts of energy. If their fields are properly oriented, they can merge w/earth's magnetic fiel.
Why does the sun appear to have a sharp edge?
The photosphere is relatively thin compared to the other atmospheric regions.
Schwarzshchild radius
The radius at which the escape speed from a collapsing star equals the speed of light
Apparent Brightness
The rate at which energy from a star reaches a detector. It falls off as the inverse square of the distance.
Homogenous
The same everywhere
Isotropic
The same in all directions
Hydrogen shell burning
The stage of star when the central nuclear fires in the interior of a solar-mass star cease. At this point the helium in the star's core is still too cool to fuse into anything heavier. With no internal energy source, the helium core is unable to support itself against its own gravity and beings to shrink
subgiant branch
The star becomes much brighter here. A low-mass star like the Sun moves off of the main-sequence and onto this branch
star's spectral classification
Spectral class B - Surf temp 20,000k Spectral class A, main sequence - Surface temp 10,000k Spectral class G, main sequence - surface temp 6,000k Spectral class K, red giant -Surface temp 4,000k Spectral class M, main sequence - surface temp 3,000k
The most rapidly blinking pulsars are those that
Spin fastest
The chain of events leading to the formation of a star:
Stage 1, 2- Interstellar Cloud contracts, and it fragments into smaller pieces Stage 3 - Fragmentation ceases Stage 4, 5 - Protostar evolves Stage 6 - New Star is Born; protons begin fusing helium nuclei in core. Stage 7 - Star reaches main sequence where it will stay for quite some time. Hydrostatic equilibrium (pressure vs. gravity) is reached.
Why are standard candles so important to astronomy?
Standard candles are easily recognizable astronomical objects whose luminosities are confidently known. They are important because they extend the distance-measurement ladder by allowing us to use its estimated luminosity in comparison to apparent brightness to figure out an object's distance.
Star A is a main sequence star of spectral type G5 and star B is a red giant of spectral type K2 - what does this mean? (ch. 17)
Star A is brighter than Star B or Star is A is hotter than Star B
Star A is a main sequence star of spectral type F2 and star B is a whit dwarf of spectral type B4. What does this mean?
Star B is hotter than star A
The total number of stars in the MWG and dividing by the age of the MWG is a way to estimate what?
Star formation rate in the MWG
How are classification schemes related to star temp and size?
Stars are classified according to the widths of their spectral lines. Because line width depends on density in the stellar atmosphere, abd b/c this density in turn is correlated w/luminosity, this stellar property is known as its luminosity class. Spectral type and lum class define as star as well as temp and lum.
Dwarfs
Stars comparible in size to, or smaller than the Sun
Why are star clusters almost ideas "laboratories" for stellar studies
Stars in clusters have the same age, similar composition, and are at the same distance away
What makes the subject of star formation so difficult and complex?
Stars live too long to be observed from birth to death
how do supernovae help recycle galactic material?
Stars make new elements by fusion - Dying star expel gas and new elements, producing hot bubbles and cooler material like dust in planetary nebulae - Further cooling permits molecules to form, making molecular clouds - Gravity forms new stars and planets in molecular clouds Where will
8 solar masses
Stars more massive than 8 solar masses form heavier and heavier elements in their cores at a more and more rapid pace
Supergiants
Stars more than 100 times larger than the Sun
Giants
Stars up to 100 times larger than the Sun
Why was supernova 1987A so important?
Studying supernovae like SN 1987A is important because the exploding stars create elements, such as carbon and iron, that make up new stars, planets, and even humans. The iron in a person's blood, for example, was manufactured in supernova explosions. SN 1987A ejected 20,000 Earth masses of radioactive iron
Solar Magnetism & Sunspots
Sunspots are directly tied to the structure of the sun's magnetic field. The intense magnetism in the sun can tap a photon and create what appears to be a cool spot on the surface of the sun. These "cool spots" are called sun spots.
Main Sequence
Surface temp ranging from 3K to over 30K (M-O). Stretches from hot blue supergiants and blue giants through intermediate stars such as the Sun. Most main-sequence stars are red dwarfs. Blue super-giants are rare. 9% are in the white-dwarf region and 1% are in the red-giant region
What kind of variable stars are pre-Main Sequence stars undergoing gravitational contraction and exhibiting changes in their luminosities?
T Tauri
Roche-lobe
Teardrop shaped which defines the region of space within which matter belongs to the star.
What factors determine the suitability of a star as the parent of a planet on which life might arise?
Temperature
What physical property of a star does the spectral type measure? (ch. 17)
Temperature
What does the observed acceleration of the universe mean?
That dark matter exists
Outline the processes that led to life on Earth. Why is life so difficult to define in general?
The 7 evolutionary phases that have contributed to development of life on our planet are: particulate, galactic, stellar, planetary, chemical, biological, cultural. 1) matter formed from energy and died seeding the interstellar medium with heavy elements so that, when our Sun formed billions of years after the first star blazed, Earth would form along with it. Eventually, life on Earth would form.
Where did the Big Bang occur?
The Big Bang did not happen at any particular location in space, because space itself was being compressed to a point at that instant - the Big Bang happened everywhere at once.
Homogenity and isotropy, taken as assumptions regarding the structure and evolution of the universe, are known as what?
The Cosmological Principle
What properties of the universe determine whether it will or will not expand forever?
The DENSITY and MASS of the universe will determine this. If the universe is OVER critical density (9x10 to the power of -27kg/m3) then it will continue to expand until everything simply disappears and the Milky Way becomes cold and dark.
The best evidence for supermassive black holes in the center of galaxies what?
The absence of stars there
From the 1970's to the present, the accepted value of H has almost doubled. What does this mean?
The age of the universe is twice as old as we originally believed
What is about the spectra of quasars that was so unexpected and surprising?
The amount of redshifting is very large, they have very high recession velocities, meaning they are receding away from us remarkably fast.
solar constant
The amount of solar energy reaching a 1 m squared at the top fo Earth's atmosphere each second
Transition Zone
The area in the sun's atmosphere located above the chromosphere (1,500-10,000km) where the temperature rises dramatically
The principle of cosmic censorship
The belief that the only connection between a black hole and the universe is the black hole's event horizon
High mass stars do not live as long as low stars stars. Why?
The burn their fuel faster
what is an important way in which winds from red-giant stars are linked to the interstellar medium?
The central star fades and cools, and the expanding gas cloud becomes more and more diffuse, eventually dispersing into interstellar space. After awhile, the glowing planetary nebula (extended region of glowing gas) disappears from view. As the cloud rejoins the interstellar medium, it plays a vital role in the evolution of our galaxy. During the final stages of the red giants life, nuclear reactions between carbon and unburned helium in the core create oxygen and in some cases even heavier elements.
How often would be expect to see a galactic supernova
The chances of us observing a galactic supernova are much greater, once every 100 years.
core-collapse supernova
The collapse stops and the core rebounds sending a violent shock wave out through the rest of the star creating an explosion.
Nebula
The concentration of dust clouds and gases in space that forms a star
Solar Wind
The constant stream of escaping particles such ash eletromagnetic radation, protons and electrons. The wind results from the high temp of the corona. the Sun sheds it mass through the solar wind. The wind is an extremely thin medium even though it carries roughly 2 mil tons of solar matter each second.
cosmic evolution
The continuous process that has led to the appearance of galaxies, stars, planets, and Life on Earth.
closed universe
The curvature in a high density universe is sufficiently large that the universe bends back on itself and is finite in extent somewhat like the surface of a sphere.
Parsec (p.423)
The distance at which a star must lie in order for its measured parallax to be exactly 1 arc second: 1 ps = 206k AU
Granulation
The effect of the solar convection zone can be seen on the surface in the form of granulation.
Stefan Boltzmann Law
The energy emitted p/unit area p/unit of time increased as the 4th power of the star's surface temperature
Energy Transport (Convection and Radiation)
The energy produced by nuclear reactions in the core of the sun creates a photon. this photon reached Earth by traveling through all of the regions of the sun over millions of years. This process takes such a long time thanks to its many collisions with atoms in the sun. Eventually, the photon makes its way to the convection zone and is carried to the photosphere via radiation. Solar winds pick up the photon and it makes its way to Earth. (p394)
What is the Big Bang?
The event that started the expansion of the universe
This is not evidence of for supernovae in our galaxy:
The existence of binary stars in our Galaxy.
According to Hubble's Law, the greater the galaxy's redshift:
The farther it is from us
Particulate evolution
The first step in cosmic evolution
radio lobes
The jets transport energy from the nucleus where it is generated to these lobes - lie far beyond the visible portion of the galaxy where it is radiated into space.
From what interstellar medium do stars develop?
The matter among the stars is collectively termed the interstellar medium. A star forms when part of the interstellar medium begins to collapse under its own weight.
general theory of relativity
The modern replacement for Newtonian gravity. Describes gravity in terms of the warping, or bending of spacetime by the presence of mass.
This relationship concerning the mass of protostars is false: (Ch. 19)
The more massive ones will be made of the heaviest elements.
Heliosmology
The study of solar surface patterns. Started in the 1960's where measurements of the Doppler shifts of solar spectral lines revealed that the surface of the sun vibrates as a result of internal pressure that reflects off of the photosphere and repeatedly cross the solar interior. Analysis of these surface patterns allow scientists to understand and study conditions far below the sun's surface.
event horizon
The surface of an imaginary sphere, of radius equal to the Schwarzschild radius - surrounds a black hole
What is a characteristic of a main sequence star?
The surface temp of main sequence stars range from about 300 K to 30,000 K
Describe the four rungs in the distance-measurement ladder used to determine the distance to a galaxy lying 5 Mpc away
The techniques show in the the bottom 4 rungs of the Extragalactic Distance Ladder are: - radar ranging - stellar parallax - spectroscopic parallax - variable stars And they take us as far as the nearest galaxies. To go further, new techniques, such as the Tully-Fisher relation, must be used.
transition zone
The temp increased from a few thousand to around a million kelvins
What current theory is the basis for star formation?
The theory of low-mass star formation
Where will the Sun be found on the H-R diagram when it is in the Red-giant branch?
The top right
Luminosity of the Sun
The total rate at which energy leaves the sun's surface. Just under 4x10 to the 26th watts. It is measured by multiplying the rate at which solar energy falls on each square meter of the sphere (the solar constant) by the total surface surface area of our imaginary sphere) (p.390)
Bell Labs and Princeton
The two teams involved in the discovery of the cosmic microwave
What are the uncertainties in Hubble's constant's value?
The uncertainty in Hubble's constant translates directly into similar uncertainty in all distances determined from Hubble's law.
What does the Hubble law imply about the history of the universe?
The universe had a beginning and has expanded since, giving it a finite age
Closed Universe
The universe will someday stop expanding and being collapsing inward
Upon what data do measurements of sizes of eclipsing binaries depend
Their Doppler shifts and durations of states of their eclipses
Why do we feel type O and B stars are poor candidates for extraterrestrial life?
Their lifetime is too short
why can't black holes, interstellar gas, and planets be plotted on the H-R diagram
Their properties simply won't allow to be plotted on the H-R diagram. To plot a star on the H-R diagram, you must know the luminosity and temperature but these things don't possess both of these characteristics therefore cannot be plotted.
How many of the factors in the Drake equation are known with any degree of certainty? What factor is least well known?
There are 8 factors in the Drake equation. the longevity of technological civilizations in totally unknown
Why are measurements of globular cluster ages important to cosmology?
These ancient star clusters are thought to have formed at around the same time as our galaxy, so they date the time of galaxy formation.
What do observations of distance supernovae tell us about the expansion of the universe?
They allow astronomers to measure changes in the rate of expansion of the universe. In a decelerating universe, supernovae would show a greater increase in redshift than predicted by Hubble's law. In an accelerating universe (such that we've observed), there is more of a decrease in redshift than predicted by Hubble's law.
Why are white dwarfs hard to observe?
They are dim
This is true of spiral galaxies
They are relatively rare in regions of high galaxy density.
How do astronomers measure temperature of a star?
They meausre their brightnesses through two or more optical filters and then fitting a blackbody curve to the results. The measurement of the amount of starlight received through each member of a set of filter is is called photometry.
Why don't stars live forever?
They use their fuel
What do Viking, Pathfinder, and two Mars Rovers have in common?
They were all designed to investigate Mars' potential for life
Why is it odd that the binary system Algol consists of a low mass red giant orbiting a high-mass main-sequence star? How long did Algol come to be in this configuration?
This is odd because the more massive main sequence star should have evolved faster than the less massive component. If the two stars are formed at the same time (as is assumed to be the case) there should be no way that the 0.8 solar mass star could be approaching the giant stage first. Something has modified the evolution of the Algol system. Astronomers think that Algol started off as a detached binary, with both components lying well within their respective Roche lobes. Star 1 ascended the giant branch and it overflowed it's Roche lobe and gas began to flow into star 2. This transfer of matter had the effect of reducing the mass of star 2, which in then caused the Roche lobe of star 1 to shrink as it's gravity decreased.
The interstellar cloud from which our Sun formed was what?
Thousands of times more massive than the sun
Saturn's moon
Titan & Enceladus
gravitional redshift
To a distant observer, this would be the light leaving a shaceship is falling.
On an H-R diagram, a prostar would be: (Ch. 16)
To the top right of the main sequence and higher up than the Sun
Urey-Miller Experiment
Took a mixture of the materials thought to be present on Earth long ago-a "primordial soup" of water, methane, carbon dioxide, and ammonia - and energized it by passing an electrical discharge (lightning) through the gas.
The area in the Sun's atmosphere located above the chromosphere (15-10,000km) where the temp rises dramatically is which zone?
Transition Zone
supernovae
Type I - hydrogen poor, have a light curve similar in shape to that of a nova. Type II - hydrogen rich, have a characteristic plateau in the light curve a few months after maximum.
If it gains sufficient mass, a white dwarf can become a
Type I supernova
a recurrent nova could eventually build up to a
Type I supernova
How do mechanisms responsible for Type I and Type II supernovae explain their observed differences?
Type I supernova will exhibit no hydrogen lines on a light spectrum. This is because there is no hydrogen involved in this process, and very little hydrogen exists in these stars. This is because the star has already become a white dwarf, its elemental layers have already been depleted. This type dies due to a carbon-detonation which happens when an accreting white dwarf exceeds Chandrasekhar mass (1.4 solar masses). The electrons are no longer able to withstand the pull of gravity and the stars temp begins to rise, causing frequent carbon fusion. This fusion causes the star to collapse. - Type II supernova will show hydrogen lines, because hydrogen is still very present at the time of the collapse of this star. The disappearance of the electrons and escape of neutrinos make the core of a large star very unstable (equilibrium of gravity and pressure is now off, gravity is taking over). Neutrons in the core are now extremely dense, and neutrons offer resistance to further compression of the already shrinking core, slowing the gravitational collapse. But by the time the collapse is halted, the core has overshot its point of equilibrium and is extremely dense. The core then begins to rexpand, and like a fast-moving ball hitting a brick wall and bouncing back, the core becomes compressed, stops, then rebounds. An enormously large shock wave sweeps through the star at high speed, blasting all the overlying layers, including the heavy elements, into space.
core collapse supernova
Type II
The making of an abundant iron nuclei is typical of
Type II supernovae
The least common type of star in our Galaxy
Type O Giants
synchroton radiation
Type of nonthermal radiation produced by high speed charged particles, such as electrons, as they are accelerated in a strong magnetic field - Reprocessing mechanism for radiation in active galaxies - Not associated with temperature but frequency; intensity decreases with increasing frequency
Magnitude scales
Used by optical astronomers to express and compare stellar brightnesses. The greater the magnitude, the fainter the star. a different of five magnitudes corresponds to a factor of 100 in apparent brightness
What is the nearest huge cluster of thousands of galaxies, to which the Local Group may belong
Virgo cluster
At what stage of evolution do T-Tauri stars occur?
When a protostar is on the verge of becoming a main sequence star
Nuclear fusion
When nuclei of hydrogen atoms join together to form helium and they release during the energy process
When do stars leave the main sequence?
When the hydrogen in their cores is exhausted. The Sun is about halfway through its life on the main sequence and will be through it in about 5 billion years
Active Regions
Where solar activity tends to be concentrated
Red Giant branch
Where stars go after they are on the subgiant branch
if you were designing a SETI experiment, what parts of the sky would you monitor?
Where the moons of saturn and jupiter lie. pointing towards mars or towards F, g, and K type stars
A star like the Sun will end up a
White Dwarf
Iron
Whose nuclei can neither be fused together nor split to produce energy. As a star's iron core grown in mass, it eventually becomes unable to support itself against gravity and begins to collapse. At the high temps produced during the collapse, iron nuclei are broken down into protons and neutrons.
Is it possible to determine the age of a star simply by noting its position on the H-R diagram?
Yes - stars such as white dwarfs tend to lie on the lower left region of the H-R diagram and we know that white dwarfs are just the core remnants of a star. High mass stars such as red supergiants tend to be found at the top right of the H-R diagram and these stars have used up most of their fuel.
In the formation of a star cluster with a wide range of stellar masses, is it possible for some stars to die out before others have finished forming?
`Yes
Which of these does not depend on a close binary system to occur
a Type II supernova
amino acids
a basic molecule of life - build proteins, which control metabolism
Nucleotide bases
a basic molecule of life - make up DNA
In active galaxies, their central engines may be temporarily fed by:
a close encounter with a neighbor galaxy
black dwarf
a cool faded white dwarf
characteristics of an open cluster of stars
a few hundred, mainly main sequence stars
Within 30Mpc of the Sun, there are about how many galaxies?
a few thousand galaxies.
The likely progenitor of a type I supernova is:
a mass-transfer binary, with the white dwarf already at 1.3 solar masses
Apparent magnitude
a measure of apparent brightness.
Spectroscopic parallax
a method of determining a stars luminosity and estimated distance
the total energy emitted by the brightest nova explosions is about
a million Suns
dark energy
a mysterious repulsive force that exists through all space
In order of visual luminosity at the star, which is the most luminous
a nova
A loop of gas following the magnetic field lines between sunspots poles is:
a prominence
What is a loop of gas following the magnetic field lines between sunspots poles?
a prominence
the water hole
a region in the radio range of the electromagnetic spectrum near the 18cm line of hydroxl and the 21cm line of hydrogen where natural emissions from the Galaxy happen to be minimized.
x-ray burster
a result of gas building up on a star's surface so the star eventually will become hot enough to fuse hydrogen - explosive burning
In the closed universe model, the geometry of spacetime in two dimensions resembles the surface of what:
a sphere
Nova
a star that suddenly increases greatly in brightness, then slowly fades back into its normal appearance over the period of months. It is the result of a white dwarf in a binary-system drawing hydrogen rich material from its companion.
As seen in 1987, when two silicon 28 nuclei fuse, or when seven alpha particles are added to a Si-28 nucleus, the initial result in either case is:
a supernova explosion
A neutron star is about the same size as:
a u.s. city
For which of these forms of life is it hardest to apply present criteria for life based on its behavior when isolated?
a virus
protostar
a warm-very luminous object that emits mainly infrared radiation It forms as a collapsing prestellar fragment heats up and becomes denser. Eventually, a protostar's central temp becomes high enough for hydrogen fusion to begin and the protostar becomes a star
type II supernovae and star forming regions are related to one another because:
a. the shock waves of a supernova can trigger star formation. b. they both contain ionized hydrogen. c. as a result of both processes, lighter elements are transformed into heavier elements. d. they both involve high mass ionizing stars. ALL OF THE ABOVE
How big will the Sun be when it enters the red giant phase?
about 100 x's its current size
Of the planetary systems that may exist in our galaxy, what fraction may contain a habitable planet
about a tenth
On the H-R diagram, the Sun lies
about the middle of the Main Sequence
On an H-R diagram, a protostar would be
above and to the right of the main sequence.
Corona
above the transition zone, thin, hot upper atmosphere, 15 solar radii, the gas in the corona is hot enough to escape the sun's gravity and the corona beings to flow outward as the solar wind
The most important fact about a cluster of stars that makes them useful for studying star formation is that:
all the stars formed at about the same time.
Important organic molecules it produced by the Urey Miller experiment
amino acids
Which type of molecules, vital to our life, were found in Murchison and similar carbonacious chondrites
amino acids
Other experiments attempted to produce organic molecules by inorganic means
amino acids are united under the influence of heat which have then make protein-like blobs that behave to some extent like true biological cells. The synthosizing of of functioning living organisms using raw materials available only on Earth.
What are the basic ingredients from which biological molecules formed on Earth
ammonia, methane, carbon dioxide, and water
On the surface of a sphere, the shortest distance between two points is
an arc on a great circle
cosmic microwave background
an isotrophic blackbody radiation that fills the entire universe. Present temp is 3 K. It is direct evidence that the universe expanded from a hot, dense state.
neutron star
an ultracompressed ball of material. Extremely dense and at formation are predicted to be very hot, strongly magnetized, and rapidly rotating. They cool down, lose much of their magnetism, and slow down as they age
Intelligence
appears most favored by natural selection
How long can a star like the Sun keep burning hydrogen in its core?
approx. 10 billion years
Quasar spectra are:
are strongly red shifted
How old are all globular clusters in our Milky Way?
around ten billion years old
Stars live much longer than we do - how do astronomers test the accuracy of theories of star formation?
astronomers observe the objects in space as they appear today at different stages along their evolutionary paths.
On the H-R diagram, white dwarfs like Sirius B and Procyon B lie
at the lower left
On the H-R diagram, red supergiants like Betelgeuse where?
at the top right
If we are optimistic in our assumptions about the development of life and intelligence, then the number of technological civilizations in the galaxy should equal what?
average lifetime of a civilization.
why would the discovery of bacteria on another planet be an important discovery?
bacteria are the lowest forms of life
Why do some scientists think that life originated in space
because amino acids and nucleotide bases are found in comets which is how they were brought to Earth
Why do we say the solar cycle is 22 years long?
because every 11 years, the poles on the sun shift.
Why isn't it correct to say that the expansion of the universe involves glaxies flying outward into empty space?
because it's space that is actually expanding
Why is the hypothesis that life on Earth came from outer space considered plausible?
because many meteorites contain complex organic molecules
Why do some stars have fewer hydrogen lines in their spectra? (p.431)
because these stars have surface temperatures below 4000K
During which step in cosmic evolution did diverse life forms begin to arise?
biological evolution
visual binary
both stars can be seen and charted
Type I Supernovae are NOT
brighter than type II supernovae
High-mass stars
burn their fuel rapidly and have much short lifetimes than the Sun
how is the theory of stellar evolution tested?
by observing star clusters, all of whose stars formed at the same time.
How are T Tauri stars characterized observationally?
by sudden changes in their brightness
What other forms of life might be possible?
carbon based life
What is generally meany by "life as we know it"?
carbon based life that originated in a liquid water environment
The other factor besides mass that influences where a star appears on the main sequence is
chemical composition of the cloud
Large molecules found in meteorites and interstellar clouds is evidence of what?
chemical evolution has taken place elsewhere in the Universe
If the material for life was introduced from space after the Earth formed, a major carried would have been:
comets
What offers proof that heavy elements were formed in stars?
comets
Galaxy clusters
consists of many galaxies orbiting one another, bound together by their own gravity
binary-star systems
consists of two starts in orbit about a common center of mass, held together by their mutual gravitational attraction
Low-mass stars
consume their fuel slowly and may remain on the main sequence for trillions of years
Barred-spirals
contain an extended bar of material projecting beyond the central bulge
supernova remnants differ from star forming regions because, although there is ionized hydrogen in both, supernova remnants
contain no ionizing stars
Synchroton radiation produces what type of spectral line?
continuous non−thermal
While a variety of factors can produce red shifts in the spectrum, the one associated with the expansion of the universe is called:
cosmological
The last step in cosmic evolution
cultural evolution
Recent work with type I supernovae at great distances suggest the universe may in fact be accelerating its expansion, a discovery attributed to a newly found
dark energy
The iron we commonly find in our surroundings came from
decay of nickel 56 and cobalt 56 in a supernova remnant.
Compared to the Sun, stars plotted near the bottom left of the H-R diagram are much
denser.
Organic material
detected on Halley's comet and observed on Hale-Bopp that implies the possibility of life on Earth originated in space
An experiment was done where "primordial soup" of water, methane, carbon dioxide and ammonia was electrified. Following this, the material was found to contain many of the amino acids found in all living things on Earth. What was the purpose of this experiment?
determine whether amino acids could have formed naturally on Earth.
Mass of a star
determines its size, temp, and brightness.
Standard candles
distance-measuring tools. Objects that are easily identifiable and whose luminosities lie within some reasonable well-defined range.
Hubble Classification Scheme
divides galaxies into several classes, depending on their appearance
Irregular galaxies
do not fit into any of the other categories rich in gas and dust site of vigorous star formation
Which type of binary can have their sizes measured directly by photometry?
eclipsing
What is the strongest radio-wavelength emitter in the solar system?
electromagnetic radiation
The greatest variation in size, mass, and luminosity occurs in:
elliptical galaxies
Quasar's spectral lines are
emission lines with large red shifts.
Radio galaxies
emit large amounts of energy in the radio part of the spectrum. The corresponding visible galaxy is usually elliptical
Tully-fischer relation
empirical correlation between rotational velocity and liminosity in spiral galaxies
Brown Dwarf
essentially they are failed stars. substellar ojects that occupy the mass range between the heaviest gas giant stars and the lightest stars. They are small, faint, and cool (growing even colder).
The alpha process tends to produce chiefly
even numbered elements
This is NOT a source of the shock waves that lead to protostars: (Ch. 16)
expanding Herbig-Haro objects
The galactic distances used to measure the accelerationof the universe are determined by observations of
exploding white dwarfs
Higher mass protostars enter the main sequence
faster and at a higher luminosity and temperature.
How long does it take for a star like our Sun to form
fifty million years
Beyond the formation of iron, nuclear energy can be produced only by
fission of heavy nuclei back toward lighter ones
spiral galaxies
flattened disks central bulges spiral arms halos consist of old stars the gas-rich disks are the sites of ongoing star formation
How do we know anything at all about the early episodes of life on Earth?
fossils
This is NOT typical of a condensing protostar:
fusion of helium into carbon in their cores
Which event marks the birth of a star?
fusion of hydrogen atoms into helium atoms
Astronomical factors in the Drake Equation
galactic star-formation rate, the likelihood of planets, and the # of habitable planets
critical universe
has a density equal to the critical value and is spatially flat
Elliptical Galaxies
have no disk contain little or no cool gas or dust hot interstellar gas is observed consist entirely of old stars range in size from dwarf ellipticals to giant ellipticals
The X-ray emission from a neutron star in a binary system comes mainly from
heated material in the accretion disk around the neutron star
What is the internal structure of a star on the asymptonic branch?
helium fusion in a shell around a core consisting mostly of carbon and oxygen
Why does the core of a massive star collapse? (p. 539)
hint - iron core can no longer support itself
Neutron capture
how elements beyond iron form
helium capture
how elements heavier than carbon tend to form
Astronomers classify elliptical galxies by:
how flat their disks appear
Nearly all of the elements found in nature were formed inside stars expect for:
hydrogen and helium
What argues in favor of the position that Mars once harbored life
ice
In the lighthouse model
if the beams sweep across us, we can observe the pulse
cosmological principle
implies that the universe cannot have a center or an edge
Most stars, probably all stars, formed
in a cluster of stars
Supernova 1987a was located
in our companion galaxy, the large Magellanic Cloud
The heaviest nuclei of all are formed
in the core collapse that set the stage of Type II supernovae
A stage 4 object can be plotted on the H-R diagram. At this stage, the star will appear
in the middle right of the diagram
A newly formed protostar will radiate primarily at which wavelength?
infrared
Star clusters have been observed within dark nebulae with:
infrared observations
star clusters have been observed within dark nebulae with
infrared observations
S0 and SB0 galaxies
intermediate in their properties between ellipticals and spirals
When we use Hubble's law to estimate the age of the universe, the result
is the same for all galaxies.
Why is the depletion of hydrogen in the core of a star such an important even
it is where the star gets its energy
What does dark energy have to do with the future of the universe?
it means that it will continue to expand
The discovery of the cosmic microwave background was important because:
it was the experimental verification of a prediction from the Big Band Theory
In order to turn a star's proper motion into its space velocity, we must also know:
its distance and radial velocity.
From stage 4 to stage 7 of star formation, the object plotted on the H-R diagram moves so that
its luminosity decreases, while its temperature increases
bipolar flow
jets of matter that flow in the directions of the protostar's poles
Cool stars can be very luminous if they are:
large
Besides its small radius, what is a neutron star's gravitational attraction due to
large mass
Remnant
left behind by a core-collapse supernova
In the spectroscopic binary system, the star showing the large blue shift is:
less massive and approaching us at this moment.
The luminous matter in the universe accounts for what percent of the total mass of the universe?
less than 4%
chromosphere
lies above the photosphere, Reddish blue hue due to the dominating hydrogen emission line, relativity dim (compared to the photosphere) due to its low density, small solar storms erupt every few minutes
Seyfert galaxy
looks like a normal spiral but has an extremely bright central nucleus. Spectral lines are very broad indicating rapid internal motion - The luminosity of Seyferts implies that the source of radiation is much less than 1 light year across
open universe
low density, finite in extent, saddle shaped
When a typical open cluster forms, which type of stars are formed most often?
low mass M type dwarfs
when a typical open cluster forms, which type of stars are formed most often?
low mass M type dwarfs
brown dwarfs
low-mass fragments that never reach the point of nuclear ignition
Which stars live the longest?
low-mass stars because they burn slower
Characteristics of Red Giants
luminous low-mass cooler surface temps orangish in appearance
The single most important determinant of the temp, density, radius, luminosity, and pace of evolution of a protostar is its
mass
the key factor in the determination of temp, density, radius, luminosity, and pace of evolution of a protostellar object is:
mass of the nebula
What produces a type-I supervnova
mass transfer onto a white dwarf pushing it over 1.4 solar masses
What produces a Type I supernova?
mass transfer to a white dwarf in a binary etc.
model
model sating that neutron stars, because they are magnetized and rotating, send regular bursts of electromagnetic energy into space. The beams are produced by charged particles confined by the strong magnetic fields.
A protostar that will eventually turn into a star like the Sun is significantly what?
more luminous
Black holes result from stars having initial masses
more than 25 times the mass of the Sun.
Young stars in a galactic disk are
mostly found in the spiral arms
Active galaxies
much more luminous than normal galaxies, have non stellar spectra, emit most of their energy outside the visible part of the electromagnetic spectrum
Hot blue giants
much more massive than the Sun
Virgo Cluster
nearest large galaxy cluster to the Local Group
in neutralization of the core, a proton and an electron make a neutron and a
neutrino
As a star evolves, heavier elements tend to form by various processes. which of the following is not one of those processes
neutronization
active galactic nucleus
nonstellar activity suggest internal motion and is associated with it
On the main sequence, massive stars do what?
not change its luminosity significantly
X-Ray busters are most similar to this phenomena:
novae
cosmological redshift
occurs as a photons wavelength is stretched by cosmic expansion
Type I Supernova - carbon detonation supernova
occurs when a carbon-oxygen white dwarf in a binary system gains mass, collapses, and explodes as its carbon ignites.
The ratio of the universe's actual density to the critical density is
ohm symbol 0
a 20 solar mass star will stay on the main sequence for 10 mil years, yet the iron core can exist for only
one day
How is technical civilization defined?
one that can communicate over interstellar distances
In Robert Frost's classic poem, when he ends with "ice will suffice", the universe is (Ch. 26)
open
If a star appears to move back and forth relative to other stars over a six-month period, this motion is due to the star's
parallax shift.
The two different kinds of surveys that have given astronomers great insight into the structure and expanse of the universe are:
pie slice and pencil beam
Electron degeneracy pressure
pressure that makes the core unable to react to the new energy source - it is the condition at the onset of helium burning where the electrons in the core can be thought of as tiny hard spheres, once brought into contact, present stiff resistance to being compressed any further.
Drake equation
provides a means of estimating the probability of intelligent life in the galaxy.
Quasars
quasi stellar - most luminous objects known. appear star-like in visible lights, spectra are usually redshifted. very distant, indicating that we see them as they were in the remote past
When the chromosphere can be seen during a solar eclipse, what color does it appear
red
When the chromosphere can be seen during a solar eclipse, what color does it appear?
red
pulse period
rotation period of the neutron star
A hypernova creates:
short−duration gamma−ray bursts.
If a large flare is detected, when will the radio interference arrive
simultaneously
Suppose a large flare is detected optically, How long until radio interference arrives?
simultaneously
Suppose a large flare is detected optically. How long until the radio interference arrives?
simultaneously
What characterizes a main sequence star?
size, surface temp, luminosity, density, age
Amino Acids & Nucleotide Bases
some of these complex molecules, or their progenitors, may have been formed in interstellar space and then delivered to Earth by meteors or comets
The redshift of the galaxies is correctly interpreted as:
space itself is expanding with time, so the photons are stretched while they travel through space
Having nothing to do with trigonometry, which parallaxes use the width of absorption lines to estimate the star's luminosity and size and distance?
spectroscopic
A fragment of a collapsing gas cloud that comes to equilibrium with a central temp of 4m K will become a:
stage 1 protostar
Star A and Star B both an absolute magnitude of 2.0 but star A is at a distance of 50 pc and star B is at a distance of 20 pc. what does this mean?
star B appears brighter than star A but actually star B and star A are the same brightness
What are the roles of heat, rotation, and magnetism in the process of stellar birth?
stars form when an interstellar cloud collapses under its own gravity and breaks up into pieces comparable in mass to our sun. heat, rotation, and magnetism all compete with gravity to influence the cloud's evolution.
The star's color index is a quick way of determining what?
temperature.
What is the most famous G-type star?
the Sun.
Absolute magnitude
the apparent magnitude it would have if placed at a standard distance of 10pc from the viewer. It is a measure of a star's luminosity.
Assuming the conditions ripe for life and intelligence abound in the Galaxy, what factor limits the number of galactic civilizations?
the average survival time of the civilizations
time dilation
the clock would appear to slow down as it reaches the event horizon
If the initial interstellar cloud in star formation has a mass sufficient to form hundreds of stars, how does a single star from from it?
the cloud fragments into small clouds and forms many stars at one time
If the initial interstellar cloud in a star formation has a mass sufficient to form hundreds of stars, how does a single star form from it?
the cloud fragments into smaller coulds and forms many stars at one time
Most of the carbon in our bodies originated how?
the core of a red-giant star
The unusual nature of viruses (behaving as living organisms wile within them, but becoming inter while isolated) has caused scientists to consider what possibility?
the definition of life may be more complex than a simple check list.
critical density
the density of matter needed for gravity alone to overcome the present expansion and cause the universe to collapse
Stellar Parallax
the distance to stars can be measured using SP. It is the apparent shift a foreground object relative to some distant bacjground as the observer's point of view changes. to determind an object's parallax, we observe it from either end of some baseline and measure the angle through which the line of sight of the object shifts. In astronomical contexts, the angle is usually obtained by comparing photographs made from the two ends of the baseline.
Stellar nucleosynthesis
the formation of heavier elements inside stars
Within the boundaries of the constellations Coma and Virgo are found
the largest nearby super−clusters of galaxies.
The least well-know factor in the Drake equation
the longevity of technological civilizations
A critical difference between millisecond and normal pulsar is that:
the millisecond ones are speeding up, but normal pulsars slow down over time.
how do stars leave the main-sequence
the most massive stars leave first, then the intermediate-mass stars, and so on
Using the method of standard candles, we can find the distance to a campfire if we know
the number of logs used
The Drake equation calculates N. What is N?
the number of technical civilizations in our galaxy presently
How would the cosmological principle be disproved?
the observed structure of the universe depends on the direction in which we look.
eclipsing binary
the orbit is oriented in such a way that one star periodically passes in front of the other as seen from the Earth and dims the light we receive. Studies of binary-star systems often allow stellar masses to be measured.
singularity
the point where both the density and gravitational field of the star become infinite
Cultural and political factors
the probability that intelligence leads to technology and the lifetime of a civilization in the technological state
chemical and biological factors
the probability that life appears and the probability that it subsequently develops intelligence
zero-age main sequence
the region in the H-R diagram where stars lie when the formation process is over. Mass is the key property in determining a star's characteristic and life span.
Why do planetary nebulae form as rings?
the result of a runaway expansion of the star, which is way less intense than a (super)nova, which would lead to a far less organized cloud.
spectroscopic binary
the stars cannot be resolved, but their orbital motion can be detected
Although the habitable zone around a large B class star is large, we don't often look for life on planets there because:
the stars don't last long enough for life to form
The primary source of the Sun's energy is
the strong force fusing hydrogen into helium
cosmology
the study of the universe as a whole
main-sequence turn-off
the turnoff point for a star refers to the point on the Hertzsprung-Russell diagram where it leaves the main sequence after the exhaustion of its main fuel
This is NOT true about supernovae
the two types are both closely related to evolution of white dwarfs
If the density of the universe is greater than critical what will happen?
the universe is closed, gravity wins, and will shrink to the Big Crunch
If the density of the universe is at the critical density this means what?
the universe is expanding at a rate equal to the escape speed of the universe
If the density of the universe is lower than the critical density, what does this mean?
the universe is expanding at a rate greater than the escape speed of the universe
On the basis of our current best estimate of the present mass density of the universe, what do astronomers think about the universe?
the universe is finite in extent and will eventually collapse
if ohm is less than one, then
the universe will expand forever
The Chandrasekhar limit
the upper mass limit for a white dwarf
Upon what do measurements of sizes of eclipsing binaries depend?
their Doppler shifts and durations of stages of their eclipses
Stars of spectral class M do not show strong lines of hydrogen in their spectra because:
their surface temps are so cool that most hydrogen is in the ground state
In state 6 or 7 of the formation of a large cluster of stars, a nebula is formed around the cluster. Why does this happen?
there are massive O and B stars emitting high energy photons that ionize the remainder of the cloud
when a stellar iron core collapses, large number of neutrinos are formed, then:
they are captured to form heavy elements
Like parallax, proper motion is measured over intervals of exactly six months.
this statement is incorrect
In the H-R diagram, the bright blue-white stars that dominate the naked eye sky lie where?
to the top left
Characteristics of Brown Dwarfs
too little mass to sustain fusion -cooler than M stars -bright in the infrared, very faint in visible, reddish
If a star appears to move relative to other stars over a one-year period, this motion is due to the star's
true space motion
Roche lobes
two volumes of space shaped like the halves of an hourglass which enclose a binary star system and whose surface represents the smallest equipotential surface that can exist around the system.
The critical evidence for cosmic acceleration in 1998 came from two beams of astronomers, both observing what?
type I supernovae
The making of abundant iron nuclei is typical of
type II supernovae.
3 solar masses
upper limit on the mass of a neutron star. Beyond 3 solar masses, a star can no longer support itself against its own gravity. A region of
Gamma Ray bursts
very energetic flashes of gamma rays observed about once per day, distributed uniformly over the entire sky - extremely luminous
millisecond pulsar
very rapidly rotating neutron star. Found in the hearts of globular clusters. Old. Spun up by interactions with other stars.
Neutron stars Have
very strong bi-polar magnetic fields
A Type I supervnova
was originally a low-mass star
this statement about our current knowledge of elements is FALSE
we have now produced over 50 radioactive elements not occurring in nature
If the Sun were replaced by a one solar mass black hole:
we would still orbit it in a period of one year.
at what stage of evolution do T Tauri stars occur
when a protostar is on the verge of becoming a main sequence star
as a star forms - the photosphere first appears
when the protostar frms
accretion disk
where gas spirals inward and builds up on the white-dwarf's surface, eventually becoming hot and dense enough for the hydrogen to burn explosively, temporarily causing a large increase in the dwarf's luminosity.
Horizontal branch
where the star goes after the helium flash - the star now has a core of burning helium surrounded by a shell of burning hydrogen.
asymptotic-giant branch
where the star goes as helium burns in the core. It forms an inner core of non-burning carbon and the carbon core shrinks and heats the overlying burning layers. The star once again becomes a red giant and is more luminous than before.
To date, our serious searches for extraterrestrial life have been done almost entirely
with radio telescopes
What did the Wilkinson Mapping Project give us? (Ch. 26)
©o = 1, but matter (dark and visible) is only 27% of this, the rest is dark energy.
What is the force that keeps a main sequence star from collapsing on itself?
Radiation pressure
Extremophiles
Recently discovered organisms that create their energy through chemical reactions (chemosynthesis instead of photosynthesis) and life in environments previously thought too alkaline, hot, cold, dark, saline, etc. to sustain life.
Which stars on most common in our Galaxy?
Red Dwarfs - we don't see them commonly plotted on the H-R diagram because they are too dim
Static and infinite
Rejected model based on astronomical measurements and Olber's Paradox
Dark Energy
Repulsive force driving acceleration of objects at great distances
Which type of galaxy has a stellar disk, but without gas and dust
S0
planetary nebulae
Since the core of a low-mass star never becomes hot enough to fuse carbon, it continues to ascend the asymptotic-giant branch until its envelope expands and ejects this out into space
A typical protostar may be several thousand times more luminous that the sun. what is the source of this energy
From the release of gravitational energy as the protostar continues to shrink
why do the cores of massive stars evolve into iron and not heavier elements?
Fusion of heavier elements disrupts the stability of the core by requiring energy
The huge lobe radio galaxy at the center of the Virgo Supercluster is
M-87, a giant elliptical galaxy
What happens when interstellar clouds shrink?
Fragmentation ceases
Elements in the sun: Sulfur
% of total number of atoms: 0.0015 % of total mass: 0.040
Elements in the sun: Iron
% of total number of atoms: 0.0030 % of total mass: 0.14
Elements in the sun: Neon
% of total number of atoms: 0.0035 % of total mass: 0.058
Elements in the sun: Magnesium
% of total number of atoms: 0.0038 % of total mass: 0.076
Elements in the sun: Silicon
% of total number of atoms: 0.0045 % of total mass: 0.099
Elements in the sun: Nitrogen
% of total number of atoms: 0.0088 % of total mass: 0.096
Elements in the sun: Carbon
% of total number of atoms: 0.043 % of total mass: 0.40
Elements in the sun: Oxygen
% of total number of atoms: 0.078 % of total mass: .97
Elements in the sun: Helium
% of total number of atoms: 8.7 % of total mass: 27.1
Elements in the sun: Hydrogen
% of total number of atoms: 91.2 % of total mass: 71.0
What is the absolute magnitude of our Sun?
+4.8
Characteristics of White Dwarfs
- 8% of stairs in our neighborhood -hot, dim, and tiny -remnants of stars they don't create energy by fusion
How can astronomers estimate the age of an isolated star?
Estimate the ages of stars from purely spectroscopic studies (even when the stars are isolated and not in any cluster).
Jupiter's moons
Europa & Ganymede
Which type of heavy atomic nuclei are most common and why?
Even numbered elements, for helium is "giant good" for everything beyond itself
Big Bang
Event that cosmologists consider the beginning of the universe, in which all matter and radiation in the entire universe came into being.
What can't evolutionary states 1-3 be plotted on the H-R diagram?
Evolutionary stage 1-3 cannot be plotted because their surface temperatures do not meet the requirements of the diagram.
What do the assumptions of mediocracy suggest?
Life must have originated somewhere else in the cosmos
This event is NOT possible
Low mass stars swelling up to produce planetary nebulae
The most common type of star is:
Low-mass main sequence
Super-granulation
Lower levels in the convection zone also leave their mark on the photosphere in the form of larger transient patterns called supergranulation.
The H-R diagram plots what against the spectral type or temperature?
Luminosity
What are the two most important intrinsic properties used to classify starts
Luminosity & Surface Temperature
How is star brightness measured?
Luminosity=absolute brightness=energy flux and distance apparent brightness is measured using the inverse square aw. This means that the apparent brightness of a star is directly proportional to the star's luminosity and inversely proportional to the square of the distance. This apparent brightness (energy flux) is proportional to luminosity over distance squared.
How might the most common occurring stars be described, based on our stellar neighborhood?
M main sequence
Red Dwarfs
M type (Faint) Lower right. Much less massive than the Sun
The chemical elements that form the basic molecules needed for life are found where?
Natural radioactivity, lightning, volcanism, solar ultraviolet radiation, and meteorites
Neutrinos
Nearly massless particles that are produced in the proton-proton chain and escape from the Sun. they interact via the weak nuclear force. It is possible to detect a small fraction of them streaming from the sun.
Why does neutron capture work?
Neutrons have no repulsive barrier to overcome in combining with positively charged nuclei.
Do we know whether Mars ever had life at any time during its past?
No
Do we live in a flat universe?
No
How often would be expect a supernova to occur in our own galaxy?
No astronomer with modern equipment has ever observed a supernova in our galaxy, therefore the chance is very rare, only happening approximately every 100,000 years. The chances of us observing a galactic supernova are much greater, once every 100 years.
Is there enough dark matter to halt the current cosmic expansion?
No. Even with dark matter considered the universe is approximately only at 30% critical density.
Do all stars eventually fuse helium in their cores?
No. Low-mass stars never become hot enough
An extraterrestrial observer would pick up the strongest radio signals:
North America was either rising or setting for the observer.
Star size estimation
Once a star's angular is known, if its distance is also known, then its radius is determined by geometry. Most stars are too distant or small for direct measurements to be made. their sizes must be inferred by indirect means using radiation laws.
Why does the evolution of a protostar slow down as the star approaches the main sequence?
Once an object begins fusing hydrogen in its core (as in Stage 7, the last stage of a star) and est. a "gravity-in, pressure-out" equilibrium, it is destined to burn steadily for a very long time, therefore, its surface temperature and luminosity will remain unchanged for a long time.
How does Drake define a technological civilizations?
One that has a written language
compare and contrast the observed properties of open star clusters and globular star cluster
Open Clusters have much younger stars, all along the main sequence. Globular Clusters have much older stars, on the right side of the H-R diagram. They exist in the halos of galaxies.
Core-hydrogen burning
Phase of a stellar evolution where most stars spend most of their lives on the main sequence. They are stable fushing hydrogen into helium at their centers.
What do star clusters and associations have to do with star formation?
Physical interactions - close encounters and even collisions - between protostars within a star cluster may be very important in determining the properties of stars that eventually form.
The first probe carrying mankind's message to alien civilization was
Pioneer 10
What evidence is there that many supernovae have occurred in our Galaxy
Planetary nebulae
Hertsprung-Russell diagram
Plots luminosity vs. temp for several well-know stars. Surface temp is plotted along the horizontal axis (temp increased from right to left). Luminosity is potted along the vertical axis,. The cooler, dimmer stars lie along the bottom right (M&K type stars) and the brighter, hotter stars lie along the top left (O&B). The Sun is in the middle.
Hydro static equilibrium
Pressure's outward push exactly counteracts gravity's inward pull. This table balance between opposing forces is the basic reason that the sun never collapses under its own weight nor explodes in the interstellar space. Gravity and fusion reactions are in hydro static equilibrium in the sun. This info allows the model to make predictions about other observable solar properties - luminosity, radius, spectrum, and so on, and the internal details of the model are fined tuned until the predictions agree with observations
Shock waves
Produced as young hot stars ionize the surrounding gas, forming emission nebulae.
How do we know that quasars are extremely luminous?
Quasaras are very far away, therefore they appear small and unimpressive to us. However, they are extremely luminous. At their distances from our galaxy (240 Mpc) it's amazing that we can see them at all.