unit 4

In 2012, NASA's Spaceguard Survey concluded that astronomers had now identified 90% of the asteroids with diameters greater than 1 km. How could astronomers know that they had reached this goal?

The people doing the survey began to find the same objects over again, indicating they were reaching the limits of their survey

Which of the following statements about Saturn's rings is TRUE?

The rings are made of billions and billions of individual "moonlets" (small chunks)

What do astronomers think is the origin of the many irregular moons around the outer planets (irregular meaning they are orbiting backwards and/or have eccentric orbits)?

These moons were likely formed elsewhere and captured by the giant planets

How have astronomers learned what different asteroids are made of?

They examine the spectrum of the sunlight that reflects from the asteroid

The satellite which has the thickest atmosphere (so thick that it's quite a surprise for a satellite) is:

Titan

If there are at least a million asteroids, how did spacecraft like Galileo survive their trip through the asteroid belt?

although there are many asteroids, they are widely spaced (there is lots of space between them)

One of the key reasons that professional astronomers (as opposed to the public) are interested in comets is that they

are icy pieces left over from the time that our solar system formed that can give us clues about that early time

A baseball pitcher wants to impress his girl-friend with how strong his throwing arm is. On which of the following bodies would the pitcher be MOST likely to be able to throw a baseball (a fast ball) so fast it would actually go into orbit?

asteroid Ida

Why were asteroids not discovered until the 19th century?

asteroids are generally small compared to planets and require a good telescope and patient searching to spot them

The rings of the outer planets consist of

billions of chunks (of various sizes) that all orbit the equator of each planet

How were the rings of Uranus discovered?

by using the Kuiper Airborne Observatory (the telescope aboard an airplane) to observe Uranus moving in front of a distant star

More than 75% of the known asteroids:

can be found in a belt between Mars and Jupiter

Jupiter has enough mass to make 318 Earths. In contrast, Uranus and Neptune have only enough mass to make

15 Earths

In 2013, a small stony asteroid collided with the Earth above the Russian city of Chelyabinsk. What was the result?

A fireball briefly brighter than the Sun could be seen in the sky

The atmosphere of Venus is mostly carbon dioxide, and the atmosphere of the Earth has water vapor. Why are these two gases absent in the atmosphere of the satellite around Saturn called Titan?

Titan is so cold that carbon dioxide and water vapor freeze out

Two small moons in the solar system, known since the 19th century, turn out to be captured asteroids. These two moons are:

Phobos and Deimos around Mars

Which of the following worlds does NOT have a ring?

Pluto

Which world has the biggest moon relative to its own size? Not the biggest moon in terms of kilometers, but the biggest as a percentage of the size of the world it orbits.

Pluto

The comet that broke into more than 20 pieces and then collided with Jupiter in 1994 was

Shoemaker-Levy 9

A type of planet that our surveys of exoplanets are revealing around other stars, but we don't have any examples of around the Sun are:

Super-Earth's

The fact that some asteroids cluster in what are called asteroid families is probably the result of:

collisions which broke up larger bodies into a number of smaller ones

Short-period comets like Comet Halley

come back again and again at predictable intervals

Different asteroids reflect different percentages of the light falling on them. This is due to the fact that they have different:

compositions

When astronomers say that Ganymede is a differentiated body, they mean that it:

has a heavier core, surrounded by a lighter, icy mantle and crust

When a periodic comet leaves its dusty debris behind in its orbit, the Earth can intercept this debris and

have a meteor shower as the dust burns up

The synchrotron radiation (radio waves) that astronomers first observed from Jupiter in the 1950's comes from:

high speed electrons spiraling around the planet's strong magnetic field

Which of the following pieces of observational evidence does our modern "solar nebula" theory of the formation of the solar system NOT explain directly?

the plane of the orbit of Pluto

The same process that explains why astronomers see less helium in the upper atmosphere of Saturn when they take spectra also explains

the reason Saturn is warmer than we expect

Halley's Comet was given that name because Edmond Halley was

the scientist who pointed out that the orbit of the comet was such that it should return every 76 years or so

Which of the following planets does NOT have an atmosphere?

you can't fool me: all of these have an atmosphere

Which of the following is NOT a way that Jupiter differs from terrestrial planets?

its surface has many more craters from early collisions

The bluish color that makes the atmosphere of Neptune so beautiful to the human eye is caused by the interaction of sunlight with what gas?

methane

The upper clouds in the atmosphere of Neptune are composed of:

methane

Which element plays the same role on Titan as water does on Earth (existing as gas, liquid, and solid)?

methane

Three kinds of worlds are round in our solar system. Which of the following is NOT a type of world that is typically round?

minor planet (asteroid)

The world in the solar system that is most active volcanically is:

Io

Which of the jovian planets has the shortest period of rotation (the shortest day)?

Jupiter

Which of the following statements about the seasons on Jupiter is correct?

Jupiter's axis is hardly tilted so it has no real seasonal variations

Why do astronomers today think that we have an asteroid belt and not a planet between Mars and Jupiter?

Jupiter's gravity prevented material in that zone from getting together

The telescope in space that allowed astronomers to find thousands of exoplanets and exoplanet candidates by making very careful measurements during a planet transit was called:

Kepler

Between 1992 and today, astronomers using large telescopes have discovered many icy pieces that orbit in the same region as the orbit of Pluto. These are believed to be members of the

Kuiper belt

The jovian planet that has the longest year (period of revolution) is:

Neptune

The typical meteor is

a small solid particle, no bigger than a pea

At their centers, all the jovian planets have cores made of:

a solid mixture of rocky and icy materials under great pressure

If everything in the solar system is moving around, why do the Perseid meteors repeat regularly around August 11th or so?

Because the Earth in its orbit intersects the same swarm of meteor particles at the same time each year

When the Dawn spacecraft explored the largest asteroid Ceres, it discovered white spots that appear to be salt and volcanic mountains made of water ice. This led astronomers to which of the following ideas:

Ceres may have (or may have had) a liquid ocean under its crust

The Galileo spacecraft measured that the moon Ganymede had a magnetic field, indicating that its interior was at least partly melted and warm. What do scientists think is the most likely reason for this?

Ganymede is heated by tidal forces from Jupiter

The first asteroid confirmed to have a satellite (moon) was

Ida

According to our textbook, what is the best way to defend ourselves against an asteroid which is on course to collide with the Earth in 7 years?

If we do it early enough, we could explode something on or near the asteroid to deflect it slightly, so that years later it would then miss the Earth

In the far future, an entrepreneur with a large fleet of space ships decides to capture and bring to Earth some valuable asteroids. If at that time, there is a shortage of usable metals on Earth, what type of asteroids should his employees search for?

M-type

Which of the following statements about NEO's (Near Earth Objects) is TRUE?

NEO's can include both asteroids and comets that cross the Earth's orbit

In the far future, a daring interplanetary tourist wants to go "hang-gliding" on the jovian planet with the highest equatorial wind speeds. Which planet would have the fastest wind at its equator?

Neptune

Which planet in the solar system rotates the most slowly (has the longest "day")?

Venus

Which of the following statements about the tails of comets is FALSE?

a comet always has a nice long tail, even when it is far from the Sun

When two objects in orbit have periods of revolution that are simple ratios of each other (such as 1 to 2 or 1 to 3) we say that we have:

a resonance

The Red Spot of Jupiter is:

all of these

Which of the following is NOT a correct statement about the ways the jovian planets differ from the terrestrial planets?

all the jovians have satellites around them and none of the terrestrials do

What do the magnetic fields of Jupiter, Uranus, and Neptune have in common?

all three have their magnetic axes offset from the center of the planet

One of the best proofs that our theory of how the solar system formed is correct is that astronomers now observe

disks around other stars which show evidence of gaps where planets may be forming

When a chunk of cosmic material the size of a golf ball or a baseball hits the Earth's atmosphere it makes a

fireball

Astronomers have realized that the surface of Ida is older than the surface of Gaspra. How do they measure this?

from counting craters on each asteroid's surface

One of the most perplexing issues raised by the discovery of thousands of exoplanets is the existence of "hot Jupiters" -- planets with the masses and compositions of Jupiter, but orbiting closer to their stars than Mercury does in our solar system. What is our best idea currently about how such "hot Jupiters" came to be?

hot Jupiters formed further out in their star system, and then migrated inward somehow

By far the most abundant element in the giant (jovian) planets is:

hydrogen

The element that can act like a metal when it is under tremendous pressure and is probably responsible for Jupiter and Saturn's magnetism is:

hydrogen

Which of the following statements about Jupiter's magnetosphere is TRUE?

it completely covers the inner satellites of Jupiter and is one of the largest structures in the solar system

Which of the following statements about the unusual object Chiron is FALSE?

it is one of the largest asteroids, just a little smaller than Vesta

Which of the following characteristics distinguishes Uranus from every other planet in our solar system?

it rotates on an axis that is roughly parallel to the circle of its orbit

Astronomers in Hawaii discovered the asteroid now named Oumuamua. What distinguished this asteroid from all the others that had been found up to that time?

its orbit indicated it came from outside the solar system

In addition to hundreds of smaller objects they have been discovering in the Kuiper Belt recently, astronomers were surprised to find

larger bodies, with sizes as big as Pluto (now called dwarf planets)

One way to measure how long Jupiter takes to rotate is to watch the giant storms in its atmosphere go around. A more fundamental way to measure the rotation is to:

measure the changes in the planet's radio waves, which are controlled by its magnetic field

The first technique that allowed astronomers to find exoplanets involved:

measuring changes in the radial velocity (Doppler shift) of the star caused by the pull of orbiting planets

Comets appear significantly brighter in our skies as they approach the Sun because

more than one of these

The spacecraft that visited Pluto and send back our first images:

more than one of these

Astronomers estimate that there may be a trillion (a thousand billion) comet nuclei orbiting beyond Pluto. Why then do we not see more comets in our skies?

most comets remain in stable orbits beyond Pluto, only a few have their orbits disturbed and come into the inner solar system

The mountains on Pluto are made of frozen water, which at Pluto temperatures, is as hard as rock. Pluto also has a smooth, round basin which could be thought of as a frozen sea. What material is in the basin (named Sputnik) likely to be made of?

nitrogen

On which world besides the Earth could a human being step out of his spacecraft without a space suit and air tanks and be confident of surviving?

none of these

One reason we know more about the surface composition of the asteroid Vesta than about most other members of the asteroid belt is that

pieces of Vesta have landed on Earth as meteorites

When the solar system was forming, the building blocks from which the protoplanets gathered together were the:

planetesimals (a few km to tens of km wide)

How do astronomers know that the age of the solar system is about 4.5 billion years old?

radioactive dating of the primitive meteorites indicates they have that age (since they are left-over building blocks of the solar system)

What method was used to discover Pluto in 1929-1930?

take pairs of photographs several days apart and "blink" them

Which of the following is NOT a characteristic that worlds in our solar system have in common:

that all the planets have solid surfaces on which we can see impact craters

One region on Earth that has become a rich source of new meteorites in recent decades (including the meteorite from Mars that got famous because some scientists claimed they had found evidence for the building blocks of life on Mars) is:

the Antarctic

Our modern understanding of Pluto is that it is a member of

the Kuiper Belt (of trans-Neptunian objects)

The reason that worlds like the Earth are differentiated is that

the continuing impacts on a growing protoplanet eventually melted the entire body

Some years some meteor showers, such as the Leonids, feature many more meteors than in other years. What is the cause of these "meteor storms"?

the dust freed from some comets is clumpy and not evenly distributed along its orbit

What allowed the Voyager 2 spacecraft to make a "tour" of all four of the jovian planets in the late 1970's and the 1980's?

the four planets were approximately aligned on one side of the Sun and we used the gravity of each planet to speed up the spacecraft to get to the next one in its path

What is the cause of its many volcanic/geyser-like eruptions on the moon Io?

the gravitational stress of being so close to Jupiter and its other large moons heats Io's inside

Comets change as they approach the Sun in their orbits. Which of the following statements about a comet approaching the Sun is FALSE?

the gravity of the comet nucleus holds on to the evaporated material, and it all eventually freezes back into the nucleus

Which part of a comet is the DENSEST?

the nucleus

At the moment when the Voyager spacecraft got closest to Uranus, the Sun was shining directly on the planet's south pole. Uranus takes about 17 hours to rotate once on its axis. If Voyager took a photo of the south pole 8.5 hours later, what would it observe?

the south pole was brightly lit, with the Sun shining down on it

How does Saturn's F ring stay so thin (narrow), when the other rings are so wide?

there are 2 shepherding satellites on either side of it

What makes the rings of Neptune different from those of other planets we know?

they are clumpy (or bulging) in places

A key difference between the protoplanets that formed in the outer solar system and those that formed in the inner solar system was that

those in the outer solar system were in a place where ice, not just rock, condensed and thus could grow larger

Among solid worlds, which type of world is most likely to have significant geological activity?

those that are the largest (and retain heat the best)

A student in your class whom you kind-of like asks you come to watch a meteor shower. What exactly are you being invited to?

watching the left-over dirt from a comet burn up by friction as the pieces hit the Earth's atmosphere

What evidence can you give that shows the surface of Jupiter's moon Europa must be relatively young?

we see very few craters compared to the surfaces of Callisto and Ganymede

Which of the jovian planets does NOT have any satellites?

you can't fool me, all the jovian planets are accompanied by satellites