Astro 1 Unit 2 Test

Comets

-A few kilometers in size • Made of ice (both water ice and "dry ice") and dust — remnants of Solar System formation • Tails pointing away from the Sun develop due to the solar wind • Shine by reflected sunlight — i.e., comets do not produce light of their own • Highly-elliptical orbits that take them far from the Sun; as would be predicted by Kepler's 2nd Law, comets spend most of their time in the outer reaches of the Solar System — they zip by the inner Solar System and travel back out very quickly • Comets move slowly across the sky from our perspective on Earth • Short-period comets have periods < 200 years • long-period comets have much longer periods (can be 1,000s of years) and come from the Oort cloud, as much as 50,000 AU from Sun • Halley's Comet is a famous short-period comet that returns every 76 years — its last visit to the inner Solar System was in 1986; the next return will be in 2061

mars

-Mars' days and nights are similar in length to those on Earth • About half Earth's diameter; 1/10th Earth's mass • > 12 spacecraft have visited Mars; rovers explored surface • No thick atmosphere, but does have thin one that causes orangish sky; mostly carbon dioxide; only modest Greenhouse effect because the atmosphere is so thin -Average surface temperature about -65 ̊C, but can be warmer at its equator • Iron oxide ("rust") in surface rocks gives Mars its red color • Has two moons, Phobos and Deimos, but they are tiny — only 0.3 % of Mars' size • Olympus Mons (large volcano on Mars; do not need to remember name) is 3 times higher than Earth's highest mountain; Martian volcanos appear dormant • Valles Marineris (do not need to remember name) is the deepest canyon in Solar System — about 300 times size of the "Grand Canyon" on Earth • Water once existed on the surface of Mars, but it is not flowing regularly there at present; permafrosts = water ice locked beneath Martian soil • Dust storms are common; occasionally make it hard to see surface features.

vesta

-an astroid -non-spherical -dull gray and pitted with craters

Earth image

-blue seas, green and tan landmass, bight patchy white clouds

Venus image

-bright, yellowish and cloud covered -NOT a gas giant because it does not have rings

Mercury

-can only see close to sun and hard to do with the naked eye -much smaller than earth. Similar to mars in mass and radius and only a bit bigger than earth's moon -surface gravity less than on earth -temperature is extremely high on the day side and extremely low on the night side, due to lack of an atmosphere to distribute heat evenly around the planet -many craters that hold persistent ice deposits -rotates very slowly - 59 earth days to rotate, 88 earth days to orbit the sun -density = mass/volume

venus

-closest planet to earth -visible in western sky in evenings near the sun and in the eastern sky just before sunrise -slightly smaller than earth in mass and in radius -longer rotational period than its year -rotation is in the opposite direction to its orbit around the sun -dense atmosphere-mostly carbon dioxide- of gases produced by volcanic outgassing, but not dissolved in ocean like on earth, also sulfuric acid in clouds -surface is very hot because of greenhouse gases -active volcanoes, huge lava flows and Chanels, some large craters, but small meteors burn up in the thick atmosphere before they can impact to leave small craters

Neptune image

-dark and deep blue in color -few visible dark storm and cloud features -smaller ring system than Uranus

Uranus Image

-distinctive blue-green color -generally few visible cloud features -wide ring system -individual rings are very dark and thin -tipped nearly on its side

Jupiter Image

-distinctive stormy stripes -cloud bands in different colors (red, brown, white, or blueish) -great red spot -earth sized -circular storm in its Southern Hemisphere

Miranda Image

-dull and grey but which few large craters -looks wrinkled

greenhouse effect

-energy from sun heats earth -particular gases in earth's atmosphere recapture and redirect this heat back towards the surface, preventing it from escaping to space -this trapped heat is redistributed back on earth -without greenhouse gases earth's surface would be about 33 degrees cooler

earth

-fairly thick atmosphere mostly composed of nitrogen and oxygen molecules -aurora caused by solar wind particles that hit atmospheric gas and lead to emission of different colors; they are prominent near the north and south poles -plate tectonics= rocky plates on the surface of earth float on denser but more fluid rocky material, and move around -ozone protects earth from solar UV radiation; ozone can be destroyed by certain gases produced by human activity

Callisto Image

-generally darker and more cratered than the other Galilean moons of jupiter -largest crater is surrounded by what resemble frozen water ripples

Mercury Image

-grayish color and numerous craters -looks a lot like earths moon

Jupiters moons

-has more than 50 moons -four largest were discovered by Galileo in the early 17th century C; they looked like stars, but were found to orbit Jupiter — important because it helped demonstrate that Earth is not the center of Universe • Using Kepler's laws, the mass of Jupiter can be measured using the periods and semimajor axes of the orbits of Jupiter's moons; periods range from 1.8 to 17 Earth days, and Jupiter's mass is about 317 Earth masses. • You should remember the names and basic information (below) for these four largest "Galilean" moons of Jupiter...

earths moon

-lacks as much high-density material such as iron -1/4 diameter of earth -has no atmosphere; daytime sky is dark -surface gravity is 6 times stronger on the earth than on the moon -formed later than earth, from giant impact of a large object with earth

Saturn Image

-large ring system -central planet tan colored and has long stretched cloud bands -less color contrast than Jupiter

terra

-latin for land -light colored features -heavily cratered -high peaks; geologically older; highlands uplifted from impacts in early solar system

Maria

-latin for seas -dark colored -less cratered -valleys; geologically younger; filled by lava

Triton image

-looks more bumpy than cratered

Earth's moon visual

-luna -grayish and cratered -distinctive large dark maria

Ganymede image

-odd marbled look -alternating dark and light area and some bright white spots highlighting recent cratering events

Pluto image

-orbits the center of gravity of its system with the proportionally-large moon charon

Europa Image

-pale tan white covered in fine cracks -very smooth looking

Astroids

-remnants of the Solar System's formation — rocks left over when the planets form • many are in the "Asteroid Belt" between Mars and Jupiter • asteroid orbits are typically slightly elliptical • a few major types exist: carbon-rich, metallic, and silicate (stony) • we see asteroids by reflected sunlight; they do not shine visibly on their own • the orbits of some asteroids intersect Earth's orbit, and lead to meteors • most are less than 1 kilometer in size, but some are bigger • like comets, asteroids tend to move very slowly across the sky to a viewer on Earth

Titan image

-saturated orange color -complete cloud cover (cannot see sharp surface features)

Mars image

-the red planet -color of rust -has whitish caps at its poles -many craters -some prominent old volcanos -some large valleys -no significant surface water

Lo image

-yellow color with black specks

the inner four, Terrestrial ("Earth-like" / rocky) planets:

1. Mercury 2. Venus 3. Earth 4. Mars

In order to be considered a planet an object must

1. orbit the Sun (not be a moon around another object); 2. be massive enough to be nearly round; 3. clear the region around its orbit (Pluto does not; many other objects there).

Pluto is not considered a planet anymore because...

1. other similar objects were found farther from the Sun — Quaoar, Sedna, Eris 2. not like other outer planets / small; referred to as an "ice dwarf", which are very abundant beyond the orbit of Neptune

Formation of the Solar System

1. the Solar System formed 4.5 billion years ago 2. starting with cloud of gas and dust, it collapses due to its own gravity 3. as it collapses, the spinning cloud flattens and forms a disk 4. the Sun forms at center 5. "lumps" in the disk become planets 6. the regions around these proto-planetary clumps clear out (or material is absorbed) 7. only rocks and metals survive in inner region; outside, ices and gases also survive 8. takes a few tens of millions of years to form

A planet is in orbit around the Sun. The semimajor axis of the orbit is 5 Astronomical Units (AU). Use P 2 = a 3 to calculate the period of the orbit, in years.

11.2 years

the outer four, Jovian ("Jupiter-like" / gas giant) planets:

5. Jupiter 6. Saturn 7. Uranus 8. Neptune

how many earth years does it take Uranus to orbit the sun?

84

Kepler's Second Law

A line joining a planet and the sun sweeps out equal areas in equal intervals of time A planets speed is fastest when the planet is closest to the sun and slowest when it is farthest away

Jupiter

Jupiter is about 300 times the mass of the Earth, but is on average far less dense — overall about 1.3 grams per cubic centimeter (about the density of milk); it has a radius of 11 times that of the Earth. • Jupiter has a small ring system. • Jupiter is made mostly of hydrogen and helium gas. • Gaseous molecules of ammonia, methane, and water vapor also present; these lead to different colors in Jupiter's stripey, swirling appearance. • Clouds of different colors are also at different altitudes. • Windspeeds can reach 360 km/hr; the "Great Red Spot" is a giant storm larger than Earth — like an anticyclone on Earth — and has lasted for at least 300 years • Jupiter rotates rapidly (once every 10 hours), which stretches the clouds into long bands. • It takes Jupiter 12 Earth years to orbit the Sun. • Interior temperatures and pressures get very high, deep inside Jupiter's gaseous body • Hydrogen gets compressed into a liquid-metallic form. • In its very center, Jupiter is likely to have a rocky/metallic core. • Magnetic fields are 10 times stronger than Earth's due to the rotating liquid-metallic region; interaction between this magnetic field, the solar wind, and Jupiter's atmosphere leads to aurora like we see on Earth • Methane can convert to carbon soot, and high pressures inside Jupiter can compress that into diamonds (leading to "diamond rain" in Jupiter's atmosphere). • Life forms in Jupiter's atmosphere were proposed to exist by astronomers Carl Sagan and Edwin Salpeter; these speculative creatures were referred to as "sinkers," "floaters," and "hunters."

which is largest?

Jupiter's moon Ganymede

Which planet looks like the most like the moon?

Mercury

which of the following is true?

Mercury rotates exactly one and a half times for every one revolution around the Sun.

of these choices which planet has the most moons?

Saturn

Which of the following is False?

Saturn has a density of 4.8 grams per cubic centimeter, similar to metals like aluminum and iron

Which of the following is the cause of aurora?

Solar wind particles that hit the atmosphere of a planet

which of the following statements is true?

The planet Uranus is blue-green and virtually featureless.

Which of the following planets rotates in the slowest?

Venus

Which planet is this in the picture below?

Venus

Which of the following is moving fastest in the orbit?

Venus at its perihelion (closest point to sun)

The surface of Venus is hotter than the surface of Mercury because

Venus is more massive and is able to retain a thick atmosphere

Which statement about the rotation of the inner planets is true?

Venus rotates in the opposite direction from the three others

Meteors are:

asteroids or comet debris that passes into Earth's atmosphere and burns up

Which of the following objects have a dark/black sky even in the daytime

both the moon and mercury

Terrestrial Planets

general size= earth sized or smaller length of day= long day; slow rotation length of year= short due to being close to sun distance from eachother= pretty close density= high temperatures= variable, but generally warmer for being closer to the sun rings= no moons= few or none

Jovian planets

general size= much larger than earth sized length of day= short day; fast rotation length of year= long distance from the sun= very far distance from each other= spaced very far apart density= low temperatures= very cold rings= yes moons= many

impact craters

gouged out from explosions, asteroids or comets that hit the moon

how do most craters on moons form?

impact of asteroids

Which of the following is NOT required in order to classify a Solar System object as a planet (instead of a dwarf planet)?

it must be larger than all of the moons in the solar system

Main Asteroid Belt

jupiter, saturn, uranus, neptune

Ganymede

largest moon in the solar system (larger than the planet mercury); icy crust; has craters so not active now, but cracks show it once was more active

Which of the following statements is true?

lo, Earth, and Triton have active volcanos

which planet has a temperature of 800 degrees Fahrenheit on the side facing the sun and -290 degrees Fahrenheit on the side opposite the sun?

mercury

Planets going outward from the sun

mercury, venus, earth, mars

Which feature of Neptune is most responsible for its blue color?

methane in its atmosphere

Which is NOT a characteristic of a comet?

most orbit the sun in between the orbits of Mars and Jupiter

Venus is visible to us:

only near sunrise or sunset

Kepler's Third Law

p^2=a^3, where P is the orbital period and a is the semi major axis

meteorite

piece of meteor that survives atmospheric entry, hits Earth's surface

regolith

powdery dust and rocky debris that covers the moon; broken apart by small meteorites hitting moon continuously

If you know the orbital period and semimajor axis of the orbit of one of Saturn's moon, what could you determine?

saturn's mass

Lo

the closest; most coppery-yellow with black dots, which are active volcanic sites; overall very volcanically active, due to 'tidal heating' from Jupiter; low crater density; yellow color from sulfur

which of the following is the largest distance?

the distance from Jupiter to Saturn

Why do the orbits of the planets all lie in nearly the same plane?

the early solar nebula flattened into a disk

Callisto

the farthest out of the four large Galilean moons; very heavily cratered-many young craters does not get heated much, and has not changed much since its formation about the size of the planet Mercury

tidal locking

the moon rotates on its own axis with exactly the same period that it takes to travel once around the Earth; consequently, the same side of the moon always faces earth

Kepler's First Law

the planets orbit the sun in elliptical orbits with the sun at one focus. these ellipses tend to be nearly circular for the planets in our solar system

fireball

very bright meteor due to larger-than-usual chunk of debris

Europa

water-ice surface; no craters-ice movement wiped them out; liquid water ocean below icy crust

Neptune

• Discovered in 1846 (do not need to memorize exact date), based on the orbit of Uranus not looking quite right • Similar to Uranus, but a deeper blue color; atmosphere of hydrogen, helium, and methane (causes blue color); a solid core the size of earth; surrounded by a mantle of semi-fluid ices • Rapid winds and large storms/vortices; include Great Dark Spots, big storms that can come and go over the timescale of a decade • Ring structure, faint and dark; made of clumps of dust • 14 known moons • Triton (largest): thin atmosphere made of nitrogen and methane; rocky composition; reflective icy surface; ice volcanoes with liquid nitrogen, dust, or methane coming out of them; • unusual orbit suggests Triton may be a captured Kuiper Belt object

Saturn

• Galileo discovered its rings (although he did not know what they were, at the time). • the rings are incredibly thin; made of trillions of individual orbiting objects composed of dusty water-ice crystals, of various sizes • Saturn's mass is about 100 x Earth's (about 1/3 Jupiter); diameter about 10 x Earth's. • overall average density is 0.7 grams per cubic centimeter, which is less than that of water — "Saturn could float!" • the spin axis of Saturn is tilted about the same as Earth's • like Jupiter, Saturn is mostly made of Hydrogen and Helium; clouds arranged into belts and zones; temperatures cooler than on Jupiter. • More than 50 moons; by far the largest is Titan ( remember this one) — second-largest moon in Solar System; very thick nitrogen-rich atmosphere like the young Earth, but perhaps too cold for life.

Pluto

• Pluto was discovered in 1930; NASA's New Horizons probe passed it in July 2015 • 248 Earth-year period of orbit • orbit more highly-elliptical than any of the 8 planets, and not in the same plane; briefly intersects orbit of Neptune • icy ball of rock • Pluto is very small compared to the planets; Earth's Moon is 7 times as massive • Despite its size, Pluto has 5 moons; largest is Charon, over half diameter of Pluto

Pluto is now considered a dwarf planet, in the Kuiper belt

• The Kuiper belt is a disk-shaped region beyond Neptune, ranges 30 - 55 AU. • The Oort cloud (houses long-period comets) is out beyond the Kuiper belt.

Uranus

• Third-largest planet, after Jupiter (1st) and Saturn (2nd). • Orbital period is about 84 Earth years. • Uranus' thick atmosphere is made of gas, mostly hydrogen and helium, but some methane too that gives it the blue-green color • atmosphere does not have as continually prominent belts or zones, or bright clouds, like Jupiter • has liquid, icy core surrounding a smaller rocky core • Spin axis is nearly in plane of orbit around Sun (it is kind of "rolling on its side"); probably caused by collision early in its history; leads to continual near-darkness or light for 42 Earth years in a row, at its poles • Uranus has many thin, faint, dark rings made of carbon ("soot"). • 27 known moons (you do not need to know the exact number, or names, of these) • Miranda (one of the larger moons): heavily-cratered, with weird valleys and cliffs; appearance caused by upwelling of ices

Meteors

• streak across the sky very quickly — they are also called "shooting / falling stars" (they can travel up to a hundred thousand kilometers per hour) • most meteors are tiny dust particles or grains — less than a centimeter in size — that rapidly burn up in Earth's atmosphere; pieces of Solar System debris • meteors occur when an asteroid crosses Earth's orbit, or when Earth passes through a cloud of debris left behind by a comet passing through the inner Solar System (the famous Halley's Comet is reponsible for the "Orionids" annual meteor shower) • 65 million years ago a large meteor collision with Earth contributed to the extinction of dinosaurs (the "K/T event"); dust and smoke thrown into the atmosphere was greater cause of extinction — not so much the initial impact itself