Astronomy 8-

Protoplanets are thought to coalesce from planetesimals about 1 km in diameter. These planetesimals in turn form from much smaller particles. Why do these smaller particles stick together when they collide?

Chemical bonds hold the particles together

The large satellite of Saturn, Titan, has an atmosphere. Which of the following best describes this atmosphere?

Less dense than the Earth's atmosphere, consists mostly of nitrogen with a small amount of methane

What is surprising about the extrasolar planets that have been discovered?

Many of them are giant planets like Jupiter, orbiting at distances characteristic of terrestrial planets

Magnetic-field effect of Jupiter on Io:

Material from Io volcanoes captured, creating a plasma torus

Why is the surface of Mercury cooler than the surface of Venus?

Mercury, unlike Venus, does not have an atmosphere and there is no greenhouse effect.

meterorites:

Meteoroids & bits that survive passing thru Earth's atmosphere

chromosphere:

Middle layer of solar atmosphere ~104 - 105 K - Above photosphere: Layer of lower density, higher temperature gas - Characterized by spikes of rising gas - Spicules (jets of rising gas) extend upward from the photosphere to the chromosphere

Which of the following have not been found on Mars?

Moving tectonic plates

The Galilean satellites of Jupiter

formed at the same time as Jupiter from the so-called Jovian nebula.

The ______ was the first country to send a space probe to orbit the Moon, and the ______ was the first country to land a man on the Moon.

former USSR, USA

Limited gravity of small terrestrial planets could not retain

gases

We know that Neptune contains a larger amount of heavier elements than Saturn. We know this because Neptune

has a higher density than Saturn.

Which of the following molecular species plays a major role in the greenhouse effect in planetary atmospheres?

carbon dioxide

The material in the interiors of Jupiter and Saturn thought to be responsible for their powerful magnetic fields is

liquid metallic hydrogen

The Galileo spacecraft measured a magnetic field associated with Europa when Europa moved through Jupiter's magnetic field. A likely reason for this is that part of the interior of Europa consists of

liquid water

One distinct difference between Earth and its neighboring planets, Venus and Mars, is the presence of

liquid water on its surface and water molecules chemically locked into rocks

All of the following exist on Titan except

liquid water on the surface

Phobos and Deimos are moons of which planet?

mars

Which of the planets fits the following description: "a solid, cool surface, with occasional dust clouds and a thin CO2 atmosphere"?

mars

Venus and Earth have similar

mass and density.

The age of Moon rocks has been determined primarily by what method?

measurements of radioactive decay products

Io has active volcanoes that constantly replenish its surface. The source of energy for these volcanoes is

tidal heating due to Jupiter.

Extensive volcanic activity observed on Jupiter's satellite Io is caused by

tidal stresses from Jupiter and the other Galilean moons

Callisto:

⁃ Heavily cratered dirty ice. ⁃ Cratering reveals clean, white ice underneath. ⁃ No evidence of tectonics - Has a magnetic field

gravitational effect on Io:

⁃ Tidal heating keeps interior hot. ⁃ Tidal force varies over the elliptical orbit. ⁃ Varying tidal force causes flexing & internal frictional heating

neptune atmosphere:

⁃ Very active convective currents

Saturn clouds:

− Ammonia ice, water ice, ammonium hydrosulfide (NH4SH), methane ice. − Fast moving bands or belts

uranus:

− Blue hue from methane in atmosphere → thick cloud cover. − Big gas ball: has no solid outer surface. − Consists mostly of hydrogen & helium. − Metallic core → strong magnetic field - Axis of rotation almost in orbital plane (98o tilt) - Equatorial & polar temperatures about same - Rings similar to Jupiter: thin and not reflective

Saturn basics:

− Distinguished by system of rings. − Big gas ball → no solid outer surface. − Consists mostly of hydrogen & helium. − Metallic-hydrogen conducting core → moderate magnetic field. − Oblate spheroid → slightly elongated sphere

Titan is Saturn's largest satellite. of its

dense atmosphere

The internal structure of Mercury is a

dense iron core taking up almost half of the volume of the planet and a rocky mantle surrounding the core

The age of the solar system has been dated rather precisely to 4.56 billion years. What method was used to determine this number?

determining the age of meteorites by radioactive dating

planetesimals or protoplanets:

developing planets

protostars or protosuns:

developing stars

The Great Dark Spot on Neptune

disappeared sometime between the Voyager 2 flyby and when the Hubble Space Telescope photographed Neptune in 1994.

The clouds in the atmosphere of Venus consist primarily of

droplets of H2SO4 or sulfuric acid

The narrow snaking channels on the Moon are

due to lava flowing on the Moon in the past.

Earth's magnetic field is generated by

electric currents in Earth's core

Energy produced in interior =

energy radiated

When Voyager 1 flew past Io, the large satellite of Jupiter, it sent back pictures that showed

erupting volcanoes

The surface of Venus

exhibits a crust that has not broken up into moving plates but does exhibit hotspot volcanism.

The astronaut bootprint on the Moon shown in this photograph will probably

exist for >10,000 years because there is very little weathering on the Moon.

The four giant moons of Jupiter were discovered by

Galileo

The four largest satellites of Jupiter were first seen through a telescope by

Galileo Galilei

jupiter moons:

Ganymede Ice; magnetic field Callisto Dirty ice; magnetic field Io Silicates & sulfur; sulfur volcanoes Europa Water & ice - Every 7 days, Io, Europa & Ganymede line up

Jupiter's satellite Ganymede has no atmosphere, whereas Saturn's satellite Titan has a significant atmosphere. This is because

Ganymede is closer to the Sun and warmer than Titan, so any atmosphere would escape into space.

The largest satellite (moon) in our planetary system is

Ganymede, a moon of Jupiter

Protoplanets are thought to coalesce from planetesimals about 1 km in diameter. Why do these planetesimals stick together when they collide?

Gravitational attraction between the planetesimals

hydrostatic equilibrium:

Gravity pulls gas inward

core:

Heat produced via nuclear fusion

convective zone:

Heat transferred via convection

radiative zone:

Heat transferred via radiation

mid-plane of Neblua Solar Disk (NSD):

Heavy elements collide & accrete first into dust particles, then into larger clumps termed planetesimals

In what way do Uranus and Neptune differ from Jupiter and Saturn?

Hydrogen and helium make up a smaller fraction of the total mass of Uranus and Neptune.

main-sequence star:

Hydrogen burning is what defines this

Saturn

Internal structure similar to Jupiter

Which satellite of Jupiter is volcanically active?

Io

The most active volcanic object in the solar system is

Io, the inner Galilean moon of Jupiter

Which of the following objects in the solar system rotates quickest around its own axis?

Jupiter

asteroid belt exists because

Jupiter's gravitational field prevented rocky material from accreting into larger bodies

Coronal Mass Ejections (CMEs):

Large-scale magneto-plasma structures (storms) that erupt

Universe Originally:

75% hydrogen 25% helium

Which of the following is most likely responsible for the Moon's formation?

A large body impacted the Earth during its early formation. The impact ejected material into space that later formed the Moon.

Which of the following best describes a positron?

A positively charged electron

because of libration

Able to see 59% of lunar surface

The heating of the Galilean satellites of Jupiter leads to geologically active surfaces. Which one of the following best explains the source of heat?

As the satellite changes its distance from Jupiter in its elliptical orbit, it "flexes" due to the tidal forces of Jupiter. The friction that accompanies the flexing creates heat.

The moons of Mars, shown in this photo, are similar to what other objects in our solar system?

Asteroids

Jupiter cont...

Atmospheric constituency: - 86.2% Hydrogen - 13.6% Helium - 0.2% Methane (CH4) - 0.026% Ammonia (NH3) - Clouds: Ammonia & water ice (grey), ammonia hydrosulfide (NH4SH) (reddish) - Mass: 75% hydrogen, 24% helium, 1% other stuff - Temperature = 165 K (-163 oF) - Visible surface is cloud cover → - Rapid rotation creates large Coriolis effect that twists clouds into dark & light belts → run parallel to equator. - Great Red Spot → stable circular storm observed for ~300 years.

Where on Jupiter's satellite Europa is liquid water thought to exist?

Beneath Europa's surface

What property is shared by the Earth and Europa, one of Jupiter's large moons?

Both have warm oceans of water

How does the temperature in the umbra of a sunspot compare to that of the photosphere outside the sunspot?

The umbra is about 1500 K cooler.

Asthenosphere convection broke lithosphere into sections termed plates:

There are 15 large plates

List three properties of the solar system thought to be a result of how it formed

There were terrestrial and jovian planets, comets, meteoroids, and asteroids, and the way the sun, moons, and planets orbit

About 4 billion years ago Martian volcanoes were active. How did these active volcanoes affect the atmosphere of Mars?

They supplied large amounts of carbon dioxide, a greenhouse gas, to the atmosphere.

Neptune was discovered by

the careful application of Newton's laws to the motion of other planets

Venus has a high surface temperature because

the dense carbon dioxide atmosphere produces a very strong greenhouse effect.

Use Newton's law of gravity to measure

the mass of an extrasolar planet ─ Large planets close to parent star. ─ Orbits not in same plane as star's rotation.

What is the photosphere of the Sun?

the visible "surface" of the Sun

The mountain ranges on the Moon are

the walls of craters caused by impacts of large objects early in the geological history of the Moon

The protosun became a full-fledged star when

thermonuclear fusion reactions began at its center

Explain why the terrestrial planets formed smaller than the Jovian planets.

they can't obtain the same amounts of hydrogen and helium

At the present time, how many extrasolar planets have had confirmed discoveries?

thousands

What future awaits Triton, the largest satellite of Neptune?

tidal breakup as it slowly spirals closer to Neptune

earth layers:

- Crust: Uppermost, outer layer. - Mantle: Solid region under crust. - Lithosphere: Crust & upper Mantle. Solid & brittle. - Asthenosphere: Warm, plastic layer of Mantle, heated from below. Core: Liquid outer core. Solid inner core. - Inner Core: High temperature, ~6300 K, but solid because of high pressure - Molten outer core (2800-5200 km) flows → creates magnetic field.

coronal holes:

- Dark sprawling, low-density regions extending above surface where solar magnetic field opens into space. - Source of high-velocity solar wind

solar flares:

- Energy release across entire electro-magnetic spectrum from radio waves to X-rays - Charged particles accelerated outward

saturn magnetic environment:

- Field opposite sense of Earth's field. ⁃ No inclination to spin axis: North magnetic pole exactly on south rotational pole

Enceladus:

- Geologically active. Cassini image shows tiger stripes (blue lines) where plumes occur. - Thought to have ocean of liquid water with hydrogen under ice surface

Great Red Spot first seen in 1664 by Robert Hooke.

- Larger than Earth. - A high-pressure cell

Ganymede:

- Largest moon in Solar System ⁃ Strongest measured magnetic field of any moon - Heavily cratered - Long grooves, few craters

influence of magnetic field:

- Magnetic forces become tangled & break apart above sunspots, emit violent storms. - Source of space-weather events as either coronal mass ejections or solar flares

Large Impact Theory:

- Mars-size protoplanet obliquely struck Earth ~4.5 billion years ago

Io:

- Most geologically active body in Solar System - Jupiter's gravitational pull (tidal force) flexes Io like a ball of putty: − Friction generates heat. − Interior molten core. - Frequent volcanic eruptions: − Sulfur in lava -Evidence of plate tectonics

plate tectonics:

- Mountains form when one plate impacts another - Boundaries between plates are geologically active with volcanoes & earthquakes.

Jupiter structure

- No solid upper surface but distinct internal layers. - From outer layer to inner core: ⁃ Temperature increases. ⁃ Pressure increases. ⁃ Density increases. - Solid core slightly larger than Earth

Mars Surface Features

- Olympus Mons likely located over hot spot in the mantle: Olympus Mons is 27 km (17 mi) high.

titan:

- Only moon with thick atmosphere: ⁃ Nitrogen (90%), argon, methane, ethane. ⁃ N from dissociated ammonia (NH3). ⁃ Methane, ethane greenhouse gases → surface relatively warm. ⁃ Ethane may condense to form clouds & rain. - atmosphere hazy. - Large lakes of liquid hydrocarbons. - Atmospheric pressure similar to Earth - hydrocarbon lakes, probably methane or ethane - thought to have a methane rain cycle

neptune:

- Predicted using Newtonian Laws before actually discovered in 1846: ⁃ Slight deviations (perturbations) in orbit of Uranus suggested gravitational pull of another further planet

sunspots:

- Regions where magnetic field pokes through the photosphere. - Sunspots cooler than surroundings → appear darker - Thought to be caused by loops in internal magnetic field that push hot plasma (electrically charged gas) upward - Follows ~11 year cycle of minimum & maximum activity

Europa:

- Relatively young, smooth surface, few craters. - Observed cracks are ridges of fresh ice on surface → plate tectonics. - Some tidal flexing from Jupiter. - May be ocean of liquid water under surface of jumbled icebergs. - Thin atmosphere of oxygen detected. - Metallic (iron) core, rocky mantle. - Has a magnetic field

Jupiter

- Rocky core several times more massive than Earth. ⁃ Core surrounded by layer of liquid ices: Water, ammonia & methane. ⁃ Top of core → layer of helium & liquid-metallic hydrogen. ⁃ Outermost layer primarily hydrogen & helium.

moon structure:

- Small central iron-rich core ─ No indication of plate tectonics. ─ Some moonquakes Liquid outer core, slow rotation: ─ Very weak magnetic field

helioseismology:

- Study of surface patterns & pressure waves to measure temperature, pressure, & motion - Interior & surface oscillatory patterns indicate internal details

sidereal day:

- Time it takes the Earth to rotate about its axis relative to a fixed star. - About 4 minutes shorter than a solar day

the jovians

- Very large in size & mass compared to the terrestrials. - Reason: Jovians formed in cold outer solar system where H-rich gases such as methane, ammonia & water condense & freeze. As these constituents more abundant than silica, iron, nickel → outer planets had more material to form - Jupiter and Saturn, radiate more energy in UV to space than receive from Sun in visible light → contracting under own gravity, creates hot core & heat

Solar wind:

Charged particle flow from surface

Jupiter atmosphere

- Warm gas rises to cooler altitudes, condenses and forms clouds. - Three gases condense: ⁃ Ammonia (NH3) (highest alt) ⁃ Ammonia hydrosulfide (NH4SH) (middle alt) ⁃ Water (H2O) (lowest alt) - Each gas condenses at different temperature so clouds form at different altitudes. - Atmosphere windy & turbulent. - Adjacent belts with differing speeds create vortices (circular patterns or cells), largest being the Great Red Spot. - Circulation cells are split into many bands of rising & falling gases. - Effect creates the visible colored bands. - Belts: Reddish, mid-altitude - condensed ammonia hydrosulfide. Grey, high-altitude - condensed ammonia. - Zone: White, lower altitude - condensed water.

neptune basics:

- blue hue (methane) −Consists mostly of hydrogen & helium. −Has magnetic field −Fastest winds in solar system → up to 2,100 km/h (1,300 mph) ⁃ High clouds thought to be methane ice crystals. ⁃ Lower clouds hydrogen sulfide (H2S). - Magnetic field tilted ~50o to rotation axis. - Magnetic field thought to be created from ammonia ions in the liquid ammonia-water interior. - Differential atmospheric rotation: - @ poles about once every 12 hrs. - Equatorial zone about once every 18 hrs

Sun is gaseous plasma (not solid)

- does not rotate @ same speed at all locations - Process causes stress in magnetic field creating heat, intense active regions & blasts of charged particles

Earth's magnetic field created by

- flow of liquid iron in the outer core: Iron flow (electricity) in gravitational field creates magnetic field - Deflects the solar wind

moon formation:

- presence of water in trace amounts: ⁃ Possibly water ice @ poles. ⁃ Trace amount of water vapor in very thin atmosphere

Extrasolar planets are not seen directly. An observation that has been used to indirectly show they exist is

- the regular back and forth movement of the position of spectral lines of the parent stars - the change in luminosity of the parent star when a planet moves in front of it

moon composition:

- very thin atmosphere but essentially nonexistent - Gravitational field cannot retain them → Moon escape velocity too low at 2.4 km/s

photosphere:

- visible surface ~5800 K - Shell of hot, opaque gas - A bright visible surface about 500 km thick - All heat & light radiated from the photosphere

In colder outermost reaches of NSD beyond frost line* (lies between Mars & Jupiter), lighter gases made more dense from low temperatures attracted to cores → formed the

-Jovian planets ⁃ In innermost region of NSD, accreting planets could not form atmospheres as higher temperatures caused most gases to escape. - Same process in innermost region led to formation of Jovian moons, i.e. Jovian planets acted as suns.

Nebular Hypothesis: Sun + Planetesimals + Core Accretion. Model

1. Direction & orientation of planetary orbits. 2. Relative location of terrestrial & Jovian planets. 3. Size & composition of planets.

outer space:

100 km (62 mi) Karman line

Once energy 70% of way out, temperature drops to cooler

100,000 K; Too cool to ionize atoms (strip electrons) → energy transferred by convection

Each photon takes circuitous route requiring

170,000 years for energy to get out

plate structure:

237 million years ago: Americas, Europe, Africa formed single supercontinent Pangaea

The rotation period of the Moon on its axis with respect to space (its absolute rotation) is

27.3 days, the sidereal revolution period

Oldest rocks on Earth, so far found, are about

4.4 billion years old, Most rocks are 100 millions of years old

All meteorites investigated appear about same age:

4.5 billion years

Solar System Currently:

71% hydrogen 27% helium 2% other

Saturn atmosphere:

Constituents: − Hydrogen (H2) 96.30% − Helium (He) 3.25%

sun is how old

Currently ~4.5 billion years old

Orbit elliptical:

Eccentricity = 0.055. - Per Kepler's Law: Travelling fastest when closest to Earth, i.e. @ perigee, slowest @ apogee.

Europa shows no signs of cratering because

Europa is tidally heated, producing a partial melting of ices within. This liquid then rises to the surface and freezes, erasing any craters.

nebular hypothesis cont...

Nebula gas & dust began to contract about 4.56 billion years ago from own gravity or nearby supernova explosion. ⁃ As it contracted, greatest concentration occurred at center forming dense region termed the protosun. ⁃ Also with contraction, cloud flattened & spun more rapidly about axis of rotation forming a disk. ⁃ With contraction, nuclear reactions occur in protosun forming a star, i.e. the Sun. ⁃ The planets will form out of the surrounding disk of gas and dust. - conservation of angular momentum → spin increases as mass moves to center of rotation - Conservation of angular momentum also causes flattening of the disk

Why is rotation retrograde?

One theory: Giant impacts slowed & reversed rotation.

When the Big Bang happened 13.7 billion years ago, only what elements were created

Only hydrogen, helium, & trace amounts of lithium & beryllium created

interior of sun:

Opaque → does not pass radiation

corona:

Outer layer of solar atmosphere with an extended halo of low density, high T gas, ~106 K ~1 million K - Gases hot enough to escape but held by magnetic field acting on the ionized atoms & electrons. - Anomalies in the magnetic field, termed coronal holes, allow gas to escape creating the solar wind.

equinox:

Point where sun crosses the equator from south-to-north (spring) & north-to-south (autumn)

proton-proton chain reaction:

Process where 4 hydrogen nuclei combine to produce 1 helium nucleus

the Roche Limit:

Radial distance in a planet's orbit where attracted objects break apart from tidal force (gravity pull stronger on front side than back side). - particles assume differential speed - outer rings have lower orbital speed

What are the Van Allen belts?

Regions of high-energy charged particles in Earth's magnetosphere

granulation:

Regions where rolling convection currents underneath boil up to the surface - visible appearance of convection cells in the Sun's atmosphere ─ At the top of the convection cell, the rising gas is hotter & therefore brighter. ─ At the edges of the cell, the descending gas is cooler and therefore darker

Saturn rings:

Rings exist inside the Roche limit (or radius) [next slide]. - Maximum ring thickness ~ 10 m. - Rings composed of numerous particles: - Inner particles move faster than outer particles per Kepler's third law. - Particles range from 1 cm (pebble size) to 5 m (boulder size). - Mostly 10 cm (snowball size). - Consist of ice fragments or ice-coated rocks.

uranus atmosphere:

Rotation & Sun exposure produces seasonal changes

Which is the least dense planet in the solar system?

Saturn

Venus

Structure: − Probably has metal core. − Rocky crust. − Slow rotation → probably no self-induced magnetic field. Hot, plastic lithosphere: − No detectable plate tectonics. − As mantle moves, hot lava flow breaks surface to form landmasses.

neutrino:

Subatomic neutral (no charge) particle similar to electrons

positron:

Subatomic particle same mass as electron with positive charge

core cont...:

Temperature = 15 million K (15x106) As energy moves out, spreads over larger area → temperature & pressure reduced

A telescope with excellent resolution is used to monitor a protoplanetary disk about the same size as the one that became our solar system. Assume the disk has just formed. How long would we have to monitor the disk until we actually see planets?

Tens or hundreds of millions of years

general characteristics

Terrestrial planets small, rocky & close to Sun. ─ Jovian planets large, gaseous and far from Sun. ─ Temperature difference in solar nebula accounts for differences in composition terrestrial vs. Jovian

You are living at a moon base and watch the motions of the Earth and Sun in the lunar sky. What would you see?

The Earth would not appear to move significantly in the lunar sky, and the Sun would rise and set once a lunar month.

On Mars the greenhouse effect is weaker than it is on Earth and far weaker than it is on Venus. Which of the following explains this?

The Martian atmosphere is very thin and traps less infrared radiation from the surface.

hydrogen burning:

The fusion of hydrogen to helium

Jupiter Environment

The magnetosphere: ⁃ Magnetic field created by flow of liquid-metallic hydrogen, a conducting fluid. Magnetic-field strength = 4.28 Gauss (Earth = ~ 0.5 Gauss).

How do the electron and the neutrino differ?

The neutrino has no charge, a much smaller mass than the electron, and interacts weakly with matter

The surface layers of the Sun are very massive. What stops the Sun from collapsing under its own weight?

The pressure of the very high-temperature gas within the Sun supports the outer layers

Which aspect of the early solar nebula controlled the early evolution and place of formation of the terrestrial and the Jovian planets?

The temperature distribution within the nebula

What will most likely be the fate of the footprints that the astronauts left on the Moon?

They will be obliterated by micrometeorite impacts

moon crust:

Thicker crust on far side explains absence of Maria

Jupiter Rings

Thin rings consist of rock dust

synodic period:

Time for Moon to orbit Earth and reach the same position with respect to the Sun - Moon slows rotation of Earth ~0.002 sec every 100 years and spiraling away from Earth about 4 cm/yr.

Sidereal Period:

Time for one orbit around the Earth

solar day:

Time it takes for the Earth to rotate about its axis so that the Sun appears in the same position in the sky

saturn moons:

Titan Thick nitrogen (N2) atmosphere & methane (CH4) Rhea Heavily cratered surface Iapetus Most distant, orbits Dione Appears to have had tectonic activity Tethys Density less than water Enceladus Ice with geysers Mimas Ovoid shape; has massive impact crater

the van allen belts:

Two regions of ionized atoms & electrons from solar wind trapped in magnetosphere

How do the densities of Jupiter, Saturn, Uranus, and Neptune compare?

Uranus and Neptune are more dense than Jupiter or Saturn

Neptune has prominent clouds and storms in its atmosphere, but Uranus does not. Why?

Uranus does not have a significant internal heat source that could produce convection

Compared to Earth, Venus has a very weak magnetic field. The most likely reason for this is that

Venus rotates so slowly that no electric currents are set up in its core.

seismology

Vibrations on surface yield information on interior structure.

How did Venus acquire its dense carbon dioxide atmosphere?

Volcanic eruptions supplied carbon dioxide.

Why do volcanoes on Venus tend to be fewer and larger than those on Earth?

Volcanoes on Venus grow in one spot only because the crustal plates do not move, whereas on Earth the movement of the crustal plates forms a chain of volcanoes.

Solar flares are explosive eruptions on the Sun's surface associated with sudden movements of the Sun's magnetic field. At what places on the surface of the Sun do solar flares usually originate?

Within a complex group of sunspots

Is there any debris left over from the small particles that formed planetesimals, which in turn coalesced into the planets?

Yes, there is debris left over in the form of asteroids and comets.

Is there evidence for water in any form on the Moon?

Yes, there is evidence for solid water (ice) frozen in craters at the north and south lunar poles.

The material from which our solar system formed is believed to be

a cold, dark cloud of gas and dust

When Voyager 1 flew past Titan, the large satellite of Saturn, it sent back pictures that showed

a featureless globe because of the opaqueness of the thick atmosphere of Titan.

How quickly is the Moon spiraling away from Earth?

a few centimeters per year

The theory that seems to account most satisfactorily for the origin of the Moon at the present time is that

a large object collided with Earth and ejected the material that formed the Moon

The Great Red Spot is

a large, long-lived, high-pressure storm in Jupiter's atmosphere.

The structure of Mercury is

a rocky mantle surrounding a large iron core that is 75% of the planet's diameter.

What is the astrometric method used in searches for planets orbiting stars other than the Sun?

a search for tiny wobbles in the position of the star due to the gravitational pull of a planet orbiting around it

What is the Cassini division?

a wide, dark gap in Saturn's rings

The total time that the Sun will spend converting hydrogen to helium in its core is

about 10 billion years (1010 years)

Compared to that of Earth, the mass of Jupiter is

about 300 times larger

Approximately how many tectonic plates make up Earth's surface?

about ten

What gives Uranus its blue-green coloration?

absorption of the red and yellow sunlight by methane gas

The Moon is geologically

active, with many minor moonquakes occurring per day.

Maria are

ancient lava floodplains

The Moon and Mercury are similar in that they both

are heavily cratered and lack an atmosphere.

The best time to observe Jupiter from Earth is when it is

at opposition—hence closest to Earth.

The phrase "'hydrostatic equilibrium"' in the Sun refers to the

balance of gravity inward and gas pressure outward

How was Uranus discovered?

by accident, by an astronomer conducting a sky survey

The energy produced in the central core of the Sun is transported to the surface

by radiation in the layers just outside the central core and by convection in the outer layers.

The new stars then burned hydrogen to produce more helium, then burned helium to produce

carbon, calcium, oxygen and so on

Water thought to be from

comet impacts

pressure

continuously decreases with altitude

Just outside the radiation zone lies the

convection zone

Granulation on the surface of the Sun is caused by

convective currents carrying heat from beneath the surface

This photo shows solar granulation. The darker areas are regions where the gas is

cooler

sunspots are

cooler, darker regions on the Sun's surface

The bright white regions in this photo of the Sun are an upheaval of material injected into the Sun's

corona

These streaks in Neptune's atmosphere are high-altitude clouds composed of

crystals of methane ice.

Energy released in core

heats gases

The most abundant material in the universe is

hydrogen

Terrestrial planets smaller & made of elements other than

hydrogen & helium

The "fuel" of the Sun is ______, and the main products of the nuclear reactions include ______.

hydrogen / helium, neutrinos, and gamma rays

The low average density of Jupiter (about 1300 kg/m3 compared with that of water, 1000 kg/m3) indicates that this planet is composed mainly of

hydrogen and helium, in liquid or gaseous form.

nuclear fusion:

hydrogen converted to helium

Craters on Mercury appear to have been produced by

impacts from objects early in the planet's history

Stars in different stages of their evolution may generate energy using different nuclear reactions. These reactions can occur in the core or in a layer around the core. At the present, the energy of the Sun is generated

in its central core by fusion of hydrogen nuclei.

At the present time, the energy of the Sun is generated

in its central core only, by fusion of hydrogen nuclei.

Some areas of the Moon are relatively smooth, whereas other areas are heavily cratered. This is because

in some places lava flows have covered over older craters, leaving a smoother surface

The visible spectrum of the Sun

is a bright continuous spectrum, containing numerous absorption lines created by the atmosphere of the Sun.

Enceladus, a smaller satellite of Saturn, is unusual in that

it has active volcanoes.

Venus appears to be very bright in our skies at certain times because

it is relatively close to the Sun, Earth is close to it, and it is covered by very reflective clouds

Triton, the giant moon of Neptune, differs from all other major moons of planets in that

it orbits in a retrograde way, opposite to the planet's rotation.

The rotation of Mercury on its axis is unusual in that

it rotates three times on its axis in the time it takes to make two orbits around the Sun.

The Jovian planets formed in the outer solar system far from the Sun because

it was cool enough for the protoplanets forming there to capture significant amounts of hydrogen or helium

The terrestrial planets formed close to the Sun because

it was so hot in the inner solar nebula that any protoplanets forming there could not capture significant amounts of hydrogen or helium

The rotation of Uranus is unusual in that

its axis is tilted at just over 90 degrees so that it rotates on its side.

Io would probably be less active geologically if

its orbit were circular

The internal structure of Earth is a

large core of iron, partly solid and partly molten, surrounded by a thick, flexible mantle of rock

The four terrestrial planets formed through the accretion of dust particles into planetesimals, then into

larger protoplanets

The lunar mountains were created by

meteor collisions that uplifted the surface of the Moon.

The core of Earth is composed of

mostly iron

Plumes:

mostly water vapor & tiny ice particles

The majority of the extrasolar planets discovered so far are

much larger than Earth and known to be made up of large amounts of hydrogen and helium

When stars die, i.e. burn out

new elements returned to the cosmos

Which is the most abundant gas in Earth's atmosphere?

nitrogen

The Moon has

no measurable atmosphere or liquid water

A major feature of the atmosphere of Mars is

occasional strong winds and dust storms

Like Uranus, the ring system was discovered by observing the _____ of a star as the rings moved in front of it

occultation

How were the rings of Neptune first discovered?

occultation of a star as the rings moved in front of it

meteorites _____ rocks found in the solar system

oldest

Earth rotation constant:

once every 24 hrs. ⁃ Surface speed varies with latitude (solid sphere) → highest at equator

Temperature raises pressure that pushes gas

outward P → out

We now know that water exists on Mars. This water is in the form of

permafrost, polar icecaps, and a small amount of atmospheric vapor.

Radiative energy transfer via

photons* passing atom-to-atom

Neptune was

predicted to exist through its gravitational effect on Uranus.

Hot-spot volcanism is a process that

produces gigantic volcanoes on Venus and Mars but produces chains of smaller volcanoes on Earth (e.g., the Hawaiian Islands)

Energy convected to surface

radiated to space

From the center outward, the order of the layers or parts of the Sun is

radiative zone, convection zone, photosphere, chromosphere, corona

Convection currents in Asthenosphere cause

rifts & subduction zones

Which of the following types of material has the highest condensation temperature in the planetary system?

rocks and dust grains

Jupiter's Galilean satellites Ganymede and Callisto both have densities between 1000 and 2000 kg/m3. This indicates that they are composed primarily of

silicates (rocks) and ices.

Earth's mantle is composed largely of what chemical materials?

silicon-rich rocks and minerals

How many times have human beings landed on the Moon?

six

The process of accretion in planetary formation is the

slow accumulation of solid particles by gravity and collision into larger, solid objects

The Mars Pathfinder mission carried a robotic vehicle, Sojourner, to Mars. Sojourner discovered rocks that appeared to be layered like sedimentary rock. This is evidence that

standing water once existed on Mars.

The dark regions on this photo of the Sun are

sunspots

Tidal interactions between the Earth and the Moon are causing

the Earth's rotation to slow down and the Moon to move away from the Earth.

What is the corona on the Sun?

the Sun's outer atmosphere

What is the solar wind?

the Sun's outer atmosphere streaming out into space

Uranus and Neptune have no ammonia in their atmospheres because

the ammonia froze, and the ammonia ice particles sank toward the interiors of these planets.

The extrasolar planets discovered so far tend to have a much higher mass than Earth, and many of them are Jupiter's size. The reason for this is that

the methods of planet detection developed so far work best for very large planets

One of the processes carrying energy from the core of the Sun to its surface is convection. The process of convection involves

the motion of hot gases

As the solar nebula contracted, much of its material formed into a disk. This happened because

the nebula was spinning

Jupiter's magnetic field is caused by

the planet's rapid rotation coupled with liquid metallic hydrogen in its interior

People on Earth see

the same side of the Moon at all times

What is the process of chemical differentiation?

the sinking of heavy material to the center of a planet or other object and the rising of lighter material toward the surface

All the planets orbit the Sun in the same direction. This is strong evidence that

the solar system formed from a rotating cloud of gas that collapsed to form the Sun and planets

The major layers of Earth's atmosphere from the surface upward in correct order are

troposphere, stratosphere, mesosphere, thermosphere

Venus and Earth differ significantly in several ways. Earth has broken cloud cover and an atmosphere consisting mostly of nitrogen, whereas Venus has

unbroken cloud cover with a much denser carbon dioxide atmosphere.

The major planet whose spin axis lies almost in its orbital plane is

uranus

The most common surface features on Venus are

volcanoes and lava flows

The polar caps on Mars are most likely made up of

water and CO2 ices

The composition of Saturn's rings is

water ice or ice-coated rock

The large flat plains on the Moon are called maria. The maria were formed

when ancient lava flows solidified, sometimes in a very large crater.

What are zonal winds on Jupiter?

winds blowing horizontally eastward and westward in the cloud layer

axis tilt:

~23.5o, with respect to ecliptic → provides seasons

coriolis effect:

⁃ Creates cells of rising & sinking gases into powerful jet streams. ⁃ Wind velocity ~300 km/hr (190 mph).

gravitational pull of moon:

⁃ Creates tides in the oceans. ⁃ Causes bulges in Earth shape.

Jupiter basics:

− Other than the Sun, Jupiter is the largest body in Solar System. − Contains 2.5 times mass of all other planets, moons, asteroids & comets. − 300 times the mass of Earth − Big gas ball → no solid outer surface. − Consists mostly of hydrogen & helium. − Metallic-hydrogen core → strong magnetic field, ~20,000 times Earth's. − Oblate spheroid → slightly elongated sphere.

Phobos & Deimos:

− Phobos: ▪ 28 km long. ▪ Orbital period: 7.7 days. − Deimos: ▪ 16 km long. ▪ Orbital period: 30 hours.

libration:

─ Because moon orbit is elliptical, orbital motion is not in pace with its rotation: → Appears to wobble. ─ Because Moon axis not perpendicular to its orbital plane

moon features:

─ Craters everywhere. ─ Light areas → highlands. ─ Dark areas → low-lying plains or Maria (sea) - Maria concentrated on the near side - Maria are lower and relatively free of craters - Highlands higher and heavily cratered

rilles and canyons:

─ Created by lava flows or cracking of the crust. ─ No plate tectonics.

Venus atmosphere

─ Data from Mariner 2 (1962) indicated surface temperature of 673 K (752 oF). ─ Soviet spacecraft Venera 7 (1970) descended through atmosphere → measured 733 K (860 oF). ─ Cloud cover ~60 kilometers altitude, sulfuric acid (H2SO4). ─ Produces acid rain → evapo- rates before reaching surface. ─ Minimal temperature drop during long night. ─ Dense, high-pressure → pressure at surface 90 times that of Earth. ─ Composition: ▪ 95.5% carbon dioxide (CO2) ▪ 3.5% nitrogen (N2) ▪ 0.015% sulfur dioxide (SO2) ▪ Almost no water vapor. ─ Strong greenhouse effect as CO2 retains heat radiated from surface.

moon motion:

─ For Moon to complete a phase cycle, i.e. line-up with the Sun (synodic month), it must travel an additional 27o in its orbit (takes about 2 days). ─ Synodic month longer than sidereal period by about 2 days. - Moon tidally locked, meaning same side always faces Earth. - Rotational period same as orbital or sidereal period. ─ Moon exerts gravitational pull on Earth. ─ Pull sufficient so that Moon & Earth orbit around a point between their centers called center-of-mass. ─ As Earth more massive, center-of-mass close to Earth center & lies within Earth interior. - Moon does not orbit Earth → a binary system

earth formation:

─ More dense material sank toward center, less dense floated. ─ This segregation of material referred to as differentiation. ─ Outer crust primarily rocky-like material. ─ Mantle more dense & contains metals. ─ Liquid iron outer core → source of magnetic field. ─ Solid iron inner core (higher pressure).

craters:

─ Some larger craters have mountain peaks in center. ─ Formed by meteoroid impacts ─ With almost no atmosphere or water, little erosion

Thermal environment determines what materials condense (liquefy) or solidify:

─ Water & most hydrogen compounds have low condensation temperature & cannot exist near Sun → evaporate. ─ Metals & rocks have high condensation temperatures → can exist near Sun.

the nebular hypothesis:

─Gravitational collapse of rotating, diffuse, cool interstellar cloud of gas & dust forms central star plus rotating disk → the solar nebula ─As protosun continued to contract & become more dense, its temperature increased (conversion of energy of contraction to thermal energy). ─ Process termed Kelvin-Helmholtz contraction, i.e. as a gas is compressed, its pressure & temperature rise. ─ After about 10 million years, center of protosun reached a temperature of a about 10 million degrees Kelvin. ─ At this temperature, nuclear reactions ignited whereby hydrogen converted to helium, i.e. hydrogen fusion. ─ At this point, the star is born. ─ Nuclear reactions in the Sun continue to present day