Astronomy test 4

The transit method of detecting planets is most sensitive to a planet’s

volume

The Doppler method of detecting planets is most sensitive to a planet’s

mass

Which method requires a more precise alignment between the planet's orbital plane and the Earth?

Transit

Which kind of exoplanet is easier to detect?

A "hot Jupiter" (i.e. large planet near the star)

Asteroids are most "starlike" in their:

Appearance through a telescope

How many asteroids have been discovered?

Over 50,000

Which is more likely to find?

An asteroid whose orbital period has no simple whole number fraction relation to the orbital period of Jupiter. 

What is the correct order which an object experiences? from earliest to latest

Meteoroid, Meteor, Meteorite

Which kind of object leaves a trail of meteoroids which can result in meteor showers?

Comets

What kind of comet is more likely to have an orbit in the ecliptic plane?

One from the Kuiper belt

The meteors you see in a meteor shower appear to be coming from the same point in the sky.  This is because the meteors in the shower are mostly moving _______ each other.  

Roughly parallel to 

The largest asteroid in the asteroid belt is roughly the size of 

Texas

List these planets in order of the amount of atmosphere they have.  (i.e. atmosphere mass or surface pressure) fro least atmosphere to most atmosphere

Mercury, Mars, Earth, Venus

Which gas is responsible for the greenhouse effect?

Carbon Dioxide

Which planet shows differential rotation?

Jupiter

Which planet is more oblate?

oblate Jupiter

Which planet has its rotation axis tilted on its side?

tilted Uranus

Order these Jovian moons in order of geologic activity from least geologic activity to most geological activity

Callisto, Ganymede, Europa, Io

Titan is  ______ Saturn's Roche limit.

outside of

Jupiter's great red spot is most like: 

A storm

Which of the following structures does NOT show a preference for the ecliptic plane?

Oort cloud

Put these layers of the Earth's atmosphere in order from space to ground: 

Thermosphere, Stratosphere, Troposphere

Which planet has the most atmospheric layer? (i.e. the most layers that have specific labeled layers)

Earth layers

Which parts of Jupiter's atmosphere are at a higher altitude?

Whitish zones

Which Galilean moon is ^not^ in a resonance with other Galilean moons?

Callisto

The Kirkwood gaps are structures in the:

Asteroid belt

Which planet has an atmosphere which is ^not^ primarily made of carbon dioxide?

Earth

Which moon has the largest atmosphere?

Titan atmosphere

Which planet has an axis which is nearly tipped on its side?

Uranus

Which kind of planet is denser

Terrestrial

Which planets have the strangest axes of rotation

Uranus and Venus

Which of the following depends on having a liquid core

Having a magnetic core

The Coriolis effect is important for:

Hadley Cells

Which is closest to the surface of the Earth?

Troposphere

The rings of Saturn are:

Made of many small icy and rocky bits

Which orbits faster in Saturn’s rings?

A bit of rock closer to Saturn

Which is flatter?
A. Oort cloud
B. Kuiper belt
C. Neither is flatter than the other

Kuiper Belt

You find an exoplanet whose 5 moons are in
resonance with each other. Which moon is
probably more geologically active?
A. Inner moon
B. Outer moon

Inner moon

Small moons can survive

within and outside the roche limit

Large moons can survive

only outside the roche limit

The Kirkwood gaps are most closely
associated with which planet?

Jupiter

Which large moon rotates retrograde?

Titan

Which moon has an atmosphere

Titan

Consider and icy body and a rocky body of the same mass, and both roughly the same distance from the Sun. All else being equal, which is more likely to show geologic activity?

Icy body. Ice has a lower melting point than rock

Comet tails generally point

Away from the sun

Which can more easily be noticed with the naked eye?

Comets naked eye

Comet Shoemaker-Levy which struck Jupiter
was broken apart by:

Tidal forces

Why is Jupiter so much more dense than Saturn? Could a planet be smaller in size than Jupiter but greater in mass?

Jupiters lower layers of its atmosphere are way more compressed than Saturns, making Jupiter more massive. A planet could be much smaller than Jupiter but greater in mass because if much more gas were added to Jupiter, its weight would compress the interior enough to make the planet smaller rather than larger

Why does Jupiter have such a strong magnetic field?

the electrically conducting fluid region is its thick layer of metallic hydrogen. The great extent of this region, combined with Jupiter's rapid rotation, explains Jupiter's strong magnetic field.

Briefly describe how we categorize jovian moons by size. What is the origin of most of the medium-size and large moons? What is the origin of many of the small moons?

Small moons less than about 300 kilometers in diameter, medium-size moons ranging from about 300 to 1500 kilometers in diameter, and large moons more than 1500 kilometers in diameter. Most of the medium-size and large moons probably formed by accretion within the disks of gas surrounding individual Jovian planets. The small moons are probably chucks of ice and rock captured by the gravity of a massive Jovian planet.

Describe key features of Jupiter's four Galilean moons and Enceladus. Explain the role of tidal heating and orbital resonances in explaining these features.

-Io:
most volcanically active world. Hot because of tidal heating (tidal force by Jupiter, which makes Io face Jup as it orbits.) Tugs and nudges by Jup because orbital resonance.

-Europa:
surface covered by water ice. few impact craters. clear signs of water activity. Like Io has tidal heating but it is weaker. Scientists think Europa may have a secret ocean btwn mantle and icy crust

-Ganymede:
surface of water ice. Largest moon in the solar system. Magnetic field data indicate that it could have subsurface ocean of liquid water (like Europa). Has some tidal heating but not strong enough to account for an ocean.

-Callisto:
outermost Galilean moon, heavily cratered iceball. Magentic field data suggest that it could hide a subsurface ocean . Doesn't participate in the orbital resonances of the other Galilean moons and has no tidal heating.

Saturns's Enceladus:
Shows clear evidence of ongoing geological activity, few impact craters because of that (erased). Could potentially have an ocean too. Internal heat comes from tidal heating through an orbital resonance.

Describe the atmosphere and surface features of Titan. How is Titan's landscape similar to Earth's? How is it different?

Atmosphere: more than 95% nitrogen, rest is argon, methane, ethane, and other hydrogen compounds. Atmosphere thought to be a product of ethane and ammonia gas released from Titan's interior and surface. Has greenhouse effect. Cassini found shoreline wet climate.
Surface: has smog-like particles that rain out of the sky and accumulate on the ground.

Why do we think Triton is a captured moon? How might its capture be relevant to its geological activity?

it orbits Neptune “backwards” and at a high inclination to Neptunes equator. Its capture be relevant to its geological activity because Neptune provides tidal heating to triton, allowing for geological activity.

Briefly explain why icy moons can have active geology at much smaller sizes than rocky worlds.

icy compositions and tidal heating. Because they formed far from the Sun, most of the Jovian moons contain ices that can melt or deform at far lower temperatures than rock. As a result, they can experience geological activity even when their interiors have cooled to temperatures far below those of rocky worlds.

What are planetary rings made of, and how do they differ among the four jovian planets? Briefly describe the effects of gap moons and orbital resonances on ring systems.

Planetary rings are particles moving slowly relative to one another and occasionally colliding and at times being forced out at others. Saturn has several rings, separated by Cassini gap. Gap Moons are small moons within the rings that nudge the orbits of ring particles in a certain way. Shepard moons force particles in line. Reinforcement of the rings due to repeated gravitational tugs.

Explain why we think that ring particles must be replenished over time, and where we think ring particles come from.

New particles must be continually supplied to the rings to replace those that are destroyed. These new particles must come from a source that lies in each planet's equatorial plane and that consists of objects small enough to avoid being ripped apart by the tidal forces. The most likely source is numerous small "moonlets"—moons the size of gap moons— that formed in the disks of material orbiting the young Jovian planets. The small moons contribute ring particles in two ways. First, each tiny impact releases particles from a small moon's surface, and these released particles become new, dust-size ring particles. Ongoing impacts ensure that some ring particles are always present. Second, occasional larger impacts can shatter a small moon completely, creating a supply of boulder-size ring particles.

lists the jovian planets in order of increasing distance from the Sun?

Jupiter, Saturn, Uranus, Neptune

Why does Neptune appear blue and Jupiter red?

Methane in Neptune's atmosphere absorbs red light.

Why is Jupiter denser than Saturn?

Its higher mass and gravity compress its interior.

Some jovian planets give off more energy than they receive because of

ongoing contraction or differentiation.

The main ingredients of most satellites of the jovian planets are

hydrogen compound ices

Why is Io more volcanically active than our moon?

Io has a different internal heat source.

Which moon shows evidence of rainfall and erosion by some liquid substance?

Titan. Liquid Methane

Saturn's rings

are continually supplied with new particles by impacts with small moons,

Europan Ocean. Scientists strongly suspect that Europa has a subsurface ocean, even though we cannot see through the surface ice. Briefly explain why scientists think the ocean exists. Is this "belief" in a Europan ocean scientific? Explain

Europa only has a small amount of impact craters, suggesting some type of ongoing geological activity erasing the evidence of craters. Scientists suspect that the answer is either liquid water rising from an ocean that lies beneath the icy crust or interior water ice that is just warm enough to undergo convection, so that some of it rises up and flows across the surface. Europa also has enough internal heat to melt subsurface ice into liquid water. I think this belief is scientific because there is evidence to back up the fact that Europa has liquid water and oceans under its icy surface.

Brielly define asteroid, comet, dwarf planet, meteor, and meteorite. How did the discovery of Eris force astronomers to reconsider the definition of planet?

Asteroids are rocky leftover planetesimals that orbit the Sun. They appeared as points of light in telescopes. This appearance is a result of their small sizes, which make them appear point-like to most telescopes even when they are relatively nearby. Comets are icy leftover planetesimals. Comets appear as fuzzy balls with long tails to the naked eye. If you watch a comet for minutes or hours, it will remain nearly stationary relative to the stars around it in the sky. A comet may remain visible for weeks before it fades from view. The comets that appear in the night sky are the rare ones that have had their orbits changed by the gravitational influences of planets, other comets, or stars. Dwarf planets are “small bodies” large enough to be round. A meteor is only a flash of light caused by a particle of dust or rock entering our atmosphere at high speed, not the particle itself. Most of the particles that make meteors are no larger than peas and burn up completely before reaching the ground. Only in rare cases is a meteor caused by a chunk of rock large enough to survive the plunge through our atmosphere and leave a meteorite. Eris's discovery forced astronomers to confront the question of where to draw the line between planets and non-planets. After all, if Pluto was a planet, then surely the more massive Eris must be one as well. But, in that case, what about some of the other objects that are only slightly smaller than Pluto? Should they also be called planets? Or, given that all these objects have comet-like compositions, should we simply call them all comets?

describe asteroid sizes, shapes, masses, densities, and compositions. How does the total mass of all asteroids compare to the mass of a terrestrial world?

Ceres, the largest asteroid, is just under 1000 kilometers in diameter, which is a little over a quarter of the Moon's diameter. There are probably more than a million asteroids with diameters greater than 1 kilometer, and many more even smaller in size. Most asteroids are not spherical. An asteroid's shape depends largely on the strength of its gravity. Only large asteroids have gravity strong enough to have molded them into somewhat spherical shapes. The gravity of smaller asteroids is too weak to have reshaped their rocky material, leaving them looking much like potatoes. The most direct way to measure a distant object's mass is to observe its gravitational effect on another object, and to date this is possible only for the relatively few asteroids visited by spacecraft and for those that have smaller asteroids as tiny orbiting "moons." Density can offer valuable insights into an asteroid's origin and makeup. For example, the asteroids Eros and Mathilde look similar, but their densities reveal significant differences. Eros has a density of 2.4 g/cm*, which is close to the value expected for solid rock of Eros's size. In contrast, Mathilde's density of 1.5 g/cm° is so low that Mathilde must be a loosely bound "rubble pile," held together by its weak gravity, rather than a solid chunk of rock. Densities give insight into composition, but we can also learn about composition from spectra; recall that spectra of distant objects contain spectral lines that are essentially "fingerprints" left by the objects' chemical constituents. The total mass of all the asteroids together is less than any terrestrial planet.

Distinguish between primitive meteorites and processed meteories in terms of both composition and origin.

Primitive meteorites: Stony primitive meteorites are rocky mineral with small but noticeable fraction or pure metallic flakes, remnants from birth of solar system. Carbon rich primitive meteorites are rocky and contain substantial amounts of carbon compounds and, sometimes, a small amount of water bound to the rock.
Processed: Part of a larger object that "processed" original material of the solar nebula - younger than primitive meteorites. Metal rich processed are made of high-density iron and nickel mixed with small amounts of other metals. Rocky processed meteorites have lower densities and are made of rock with compositions resembling that of terrestrial mantles and crusts.

What do meteorites and spacecraft observations tell us about the geology of asteroids?

Spacecraft observations tell us meteorites represent samples of asteroids which helps us distinguish between primitive and processed meteorites.

Where is the asteroid belt located, and why? Explain how orbital resonances with Jupiter affect the asteroid belt.

The asteroid belt is located between the orbits of Mars and Jupiter. The second "belt" of asteroids would be the two sets of Trojan asteroids, which share Jupiter's 12-year orbit around the Sun.

Under what circumstances do we see a comet with a nucleus, coma, and tails? In what direction do the tails point?

For a comet plunging inward, we call this frozen center the nucleus of the comet. As the comet accelerates toward the Sun, its surface temperature increases, and ices begin to vaporize into gas that easily escapes the comet's weak gravity. Some of the escaping gas drags dust particles away from the nucleus, and the gas and dust create a huge, dusty atmosphere called a coma. The coma grows as the comet continues into the inner solar system, and some of the gas and dust is pushed away from the Sun, forming the comet's tails. Comet tails generally point away from the Sun, regardless of the direction in which the comet is traveling.

How are meteor showers linked to comets, and why do they recur at about the same time each

Meteor showers are linked to comets, and they recur at about the same time each year because the orbiting earth passes through a particular comet's orbit at the same time each year.

How do we know the Kuiper belt and Oort cloud exist? Describe each in terms of location, the orbits and number of comets within it, and its likely origin.

The Kepler belt consists of the icy planetesimals that accreted beyond the orbit of Neptune. Pluto and Triton were both observed to be from the Kuiper belt. Many Kepler belt comets have stable orbital resonances with Neptune. Oort cloud is in the outer solar system and the comets within it also orbit the Sun. Oort cloud comets are from planetesimals that were flung outward after forming between the Jovian planets.

Briefly describe Pluto and Charon. Why won't Pluto collide with Neptune? How do we think Charon formed?

Pluto is smaller than terrestrial planets and has an ice-rich composition. It is not a Jovian or a terrestrial planet. Both Pluto and Charon are made of ice-rock. Charon is larger than Pluto. Neptune orbits the Sun precisely three times for every two times Pluto's orbits, meaning Pluto is a safe distance from Neptune. Charon formed by a giant impact like how our moon is thought to be formed.

Briefly describe the evidence suggesting that an impact caused the mass extinction that killed off the dinosaurs.
How might the impact have led to the mass extinction?

The scientist team of Luis and Walter Alvarez discovered a thin layer of dark sediment that was unusually rich in iridium. Iridium is common in meteorites. An asteroid or comet hit Mexico, which sent a shower of hot debris into North America. A huge tsunami sloshed inward 1000 kilometers. Other red-hot debris rained down around the rest of the world, starting fires. Dust and smoke remained in the atmosphere for weeks and caused sunlight blockage, causing temperatures to drop. Harsh winter caused photosynthesis to stop. It also caused chemical reactions that lingered in atmosphere and into the oceans to wipe out species.

A small asteroid that orbits within the asteroid belt has an active volcano. Surprising or not?

Surprising. Small asteroids would be too small, with weak gravity and cool interiors to have active volcanoes.

The astroid belt lies between the orbits of

Mars and Jupiter

Jupiter nudges the astroids through the influence of

Orbital resonances

How big an object causes a typical "shooting star"?

a grain of sand or small pebble

Which have the most elliptical and tilted orbits?

Oort cloud comets

Which are thought to have formed farthest from the Sun?

Oort cloud comets

Why are extrasolar planets hard to detect directly?

The planets are extremely tiny compared to the vast distances between stars. Stars are typically a billion times brighter than the light reflected by any orbiting planets, so starlight tends to overwhelm any planetary light in photographs.

How can gravitational tugs from orbiting planets affect the motion of a star? Explain how alien astronomers could deduce the existence of planets in our solar system by observing the Sun's motion.

Planets exert gravitational tugs on their star, causing the star to orbit around the system’s center of mass. Alien astronomers could detect this orbital movement of the Sun and thereby deduce their existence of Jupiter, even without having observed Jupiter itself.

Briefly describe the astrometric method. What is the GAIA mission?

The astrometric method uses very precise measurements of stellar positions in the sky to look for the slight motion caused by orbiting planets. If a star "wobbles" gradually around its average position, we must be observing the influence of unseen planets. GAIA mission, launched in 2013, is in the process of obtaining astrometric observations of a billion stars in our galaxy to an accuracy that is in some cases better than 10 micro arcseconds, equivalent to the angular width of a human hair viewed from 2000 kilometers. These observations should ultimately enable GAIA to detect thousands of extrasolar planets.

Brilly describe the Doppler method. Summarize the evidence that the planet orbiting 51 Pegasi is a hot Jupiter.

The Doppler method searches for a star's orbital movement around the center of mass by looking for changing Doppler shifts in its spectrum. The data showed that the planet has about half the mass of Jupiter. Scientists therefore refer to this planet as a hot Jupiter, because it has a Jupiter-like mass but much higher surface temperature.

summarize the planetary properties we can in principle measure with current detection methods.

Orbital Period and Distance: the major detection methods (atmospheric, Doppler, and transit method) all tell us orbital period, from which we can calculate orbital distance. Orbital Eccentricity: eccentricity can be measured with the Doppler and astrometric methods. Planetary Mass: A more massive planet will cause its star to move at higher velocity around the center of mass. Planetary Size: Transit observations can detect the size/radius. Planetary Density: Can be given with transit method size and dopplers method with mass. Atmospheric Composition and Temperature: Transits and eclipses provide data on atmospheric composition and temperature; direct spectroscopy is now also possible in some cases.

Why does the Doppler method generally allow us to determine only minimum planetary masses? In what cases can we be confident that we know precise masses?

The Doppler technique detects only movement toward and away from us, we do not know the planet's orbital inclination. A very massive planet with a large inclination will give the same tugs along our line of sight to its star as a smaller planet with no inclination.

How does the transit method tell us planetary size, and in what cases can we also learn mass and density?

In the transit method, the fraction of light absorbed is the ratio of the planet's area to the star's area, so we can find the physical size of the planet. If we also measure its mass via radial velocity, we can calculate its density.

Briefly describe how TESS, CHEOPS, and direct observations should improve our understanding of extrasolar planets in coming years.

TESS and CHEOPS observe transits of extrasolar planets. They are designed to make better transit measurements for planets identified by other telescopes. CHEOPS will target stars around which planets have been discovered with the Doppler method. direct detection helps us learn more about natures of the planets, gets images of surfaces, spectra of their atmospheres, etc.

Which method could detest a planet in an orbit that is face-on to Earth?

astrometric method. The astrometric method measures the planets movement from the wobble, so it would be the best method when the planets being measured is face on.

Which one of the following can the transit method tell us about a planet?

its size

To determine a planet's average density, we can use

the transit and Doppler methods together. The Doppler method determines the mass of planet, and the transit method measures the radius of the planet, so together you can find the density.

Based on the model types shown in Figure 13.16, a planet made almost entirely of hydrogen compounds would be considered

water world

The term "super-Earth" refers to a planet that is

similar in composition to Earth but larger in size.

What's the best explanation for the location of hot Jupiters?

They formed farther out, like Jupiter, but then migrated inward.

Based on computer models, when is planetary migration most likely to occur in a planetary system?

early in its history, when there is still a gaseous disk around the star

Describe Earth's basic atmospheric structure, from the ground up. How do interactions of sunlight and gases explain the existence of each of the atmospheric layers?

The troposphere is the lowest layer; temperatures drop with altitude. The stratosphere begins where the temperature stops dropping and instead begins to rise with altitude. The thermosphere begins where the temperature again starts to rise at high altitudes. The exosphere is the uppermost region, in which the atmosphere gradually fades away into space. X-rays are absorbed by virtually all atmospheric gas. Ultraviolet photons can split water molecules and are more likely to be absorbed by weakly bonded molecules, such as ozone, which split in the process. Visible light generally passes through atmospheric gases without being absorbed, but some are scattered so that their direction changes. Infrared photons can be absorbed by greenhouse gases and warm the troposphere.

What is ozone? How does the absence of ozone on Venus and Mars explain why these planets lack a stratosphere?

Ozone is a molecule that absorbs ultraviolet light. The reason for heating to occur in the stratosphere is because the ozone’s absorption of ultraviolet light heats the stratosphere in layers. Since Venus and Mars do not have molecules that are particularly good at absorbing ultraviolet photons, they cannot have a stratosphere.

Why does convection occur in the troposphere, leading to active weather, but not in the stratosphere?

The troposphere has a drop in temperate with altitude and relatively high density of air, which is why it is the only layer with storms. Convection occurs only in the troposphere because warm air rises and cool air falls. Convection only happens when there is strong heating from below and heating from the ground in the troposphere can drive convection.

Describe Earth's global wind patterns and the role of circulation cells. How does rotation affect these cells?

The global wind patterns direction varies with latitude, equatorial winds blow from east to west, mid-latitude winds blow from west to east, and high-latitude winds blow like equatorial winds from east to west. The two factories that explain this pattern are atmospheric heating and planetary rotation. The circulation cells transport heat both from lower to higher altitudes and from the equator to the poles. Rotation affects these cells by splitting each of the two huge circulation cells into three smaller cells. The three resulting cells circulate the air somewhat like three interlocking gears, which explains the global wind directions.