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