Introduction to Astronomy Chapter 13 & 14

Why do researchers believe that asteroids in the asteroid belt are primal rocks that did not merge into a planet? The total mass of the asteroids in the asteroid belt is much smaller than that of any terrestrial planet in our solar system. Jupiter's gravity could have prevented these objects merging into a single body. The differences in chemical compositions of the asteroids are too large for them to have originated in a single body. All of the above.

All of the above

The three largest asteroids are:

Ceres, Pallas, and Vesta.

How were the rings of Uranus discovered?

photometric observations of the occultation of a star made from Earth

A comet's ________ stretches directly away from the Sun.

plasma tail

The orbits of most comets:

lie almost entirely beyond the orbit of Neptune.

The orbits of most asteroids:

lie entirely beyond the orbit of Mars.

What is erupting out of the geysers on Triton?

liquid nitrogen with carbon grit

After the discovery of Uranus, astronomers calculated its orbit and predicted its position in the sky using Kepler's laws of planetary motion, which had been known since the early 17th century. However, they soon discovered a small discrepancy between the predicted and actual positions of Uranus. As a scientist, what should you do when presented with such a conflict between prediction and observation? Select all that apply.

*think about what else might cause the observed discrepancy *consider whether Kepler's laws need to be modified to account for the new observations *verify that your observations are correct *consider that Uranus may not be a planet

About what percent of all asteroids are S-type asteroids?

15%

At the equator during the equinoxes on Uranus a day lasts:

8 hours.

In the atmospheres of the jovian planets, this component decreases, systematically, with distance from the Sun.

Ammonia

Which statement about the magnetic fields of Uranus and Neptune is FALSE?

Both pass directly through the cores of their planets, like all other fields.

The type of asteroid that would appear darkest and reflect the least light is type:

C.

Listed following are some distinguishing characteristics of comets, meteors, and asteroids. Match these to the appropriate category of objects.

Comets: *form a coma when near the Sun *most are located either in Kuiper belt or Oort cloud *visible in the sky as a fuzzy patch of light that rises and sets with the stars Meteors: *visible in the sky as a bright streak of light for only a few seconds *dust particles entering Earth's atmosphere at high speed Asteroids: *compositions similar to that of the terrestrial planets *typically orbit the Sun at approximately 3 AU

Rocky debris larger than 100 meters in diameter seen to be orbiting the Sun are called ________.

asteroids

In 1989, Neptune was found to have a huge storm named the:

Great Dark Spot.

The most abundant component of the atmospheres of Uranus and Neptune is:

Hydrogen.

What is so unusual about Pluto's orbit?

It is more inclined to the ecliptic than any of the eight planets.

The following images show four planets in our solar system. Rank these planets from left to right based on the number of moons that orbit them, from highest to lowest. (Not to scale.)

Jupiter has many moons as a consequence of its formation, in which moons formed in a disk of material surrounding it and its extended atmosphere at the time allowed it to capture numerous small bodies into orbit. Mars has two very small moons that it presumably captured at a time when it, too, had an extended atmosphere. Earth's single but surprisingly large moon is thought to have formed as a result of a giant impact. Mercury (and Venus) have no moons.

Starting with the hypothesis that a planet near Uranus was the cause of the orbital discrepancy, scientists had to develop a plan to find the unidentified planet. They started with what they knew about the discrepancies in the orbit of Uranus. Rank the steps in the order that scientists would take to discover the planet.

Knowing the discrepancy between Uranus's predicted and actual orbit, scientists and mathematicians were able to calculate the mass and orbit of a potential planet beyond Uranus that could cause such a discrepancy. Then astronomers predicted the planet's location in its orbit and began observing the sky for visual evidence of the planet. Once he had accurate star charts to work from and predictions of Neptune's location, it took Johann Galle about 30 minutes to find Neptune!

The _______ extends from about beyond the orbit of Neptune to about twice the distance of Neptune from the Sun.

Kuiper belt

The type of asteroid that would be the densest would be type:

M.

Although the atmospheres of Uranus and Neptune are very similar, the atmosphere of Neptune contains more:

Methane.

Which of the Uranian moons displays the widest range of surface terrains, suggesting some catastrophic disruption?

Miranda

Uranus and ________ are very similar in size, mass, and color.

Neptune

The following images show five planets in our solar system. Rank these planets from left to right based on their average surface (or cloud-top) temperature, from highest to lowest. (Not to scale.)

Notice that, for these five planets, temperature correlates with distance from the Sun: the closer to the Sun, the hotter the planet. Remember, however, that this is not always the case, because a planet's temperature also depends on its reflectivity and on the strength of its greenhouse effect (if any). For example, the greenhouse effect gives Venus a higher average temperature than Mercury, even though Venus is nearly twice as far from the Sun.

About a trillion comets are thought to be located far, far beyond Pluto in the ___________.

Oort cloud

When a formal definition of a planet in the solar system was adopted, Pluto was reclassified as a dwarf planet. What characteristic of planets does NOT describe Pluto? Planets orbit in ellipses with low eccentricity. Planets are approximately spherical. Planets orbit the Sun. Planets have cleared the neighborhood around their orbit. Planets orbit in or very near the ecliptic plane.

Planets have cleared the neighborhood around their orbit.

We now recognize that the largest Kuiper Belt Object could be ________, discovered almost a century ago.

Pluto

The following images show five planets in our solar system. Rank these planets from left to right based on the amount of time it takes them to orbit the Sun, from longest to shortest. (Not to scale.)

Recall that the time it takes a planet to orbit the Sun is called its orbital period, and that Kepler's third law tells us that orbital period increases with distance from the Sun. That is why the ranking order for orbital period is the same as the ranking order for distance from the Sun.

Which of the following is true about the seasons on Uranus?

The Uranian rotation axis produces some extreme seasonal effects.

Many scientific discoveries are made by chance. While studying one phenomenon, a scientist may discover a different one. Such was the case when William Herschel discovered the planet Uranus in 1781. Herschel was charting faint stars in the sky, when he discovered something that was not a star. How can astronomers tell the difference between a star and a planet? The following diagram depicts the sky as it would have appeared to Herschel when he first observed Uranus in 1781, as well as the same part of the sky over the next several nights. Label the indicated objects as stars or planets. Drag the labels onto the diagram to identify the star(s) and planet(s).

The diagrams illustrate how Herschel observed the same portion of night sky over several consecutive nights. He observed an object dim enough to be a star, but unlike the stars in the background, this object's position changed from night to night. It moved too slowly to be a nearby comet. Therefore, the object must, instead, be a large body orbiting the Sun quite distant from Earth. Quite accidentally, he had discovered a new planet, which was later named Uranus.

The following figures show four positions (1-4) of a comet during its orbit of the Sun. Also shown is the orbit of the Earth around the Sun. Rank the positions of the comet from left to right based on the size of its tail, from shortest to longest. (Not to scale; tails not shown.)

The length of the tail depends primarily on the distance of the comet from the Sun. It is longer when the comet is closer to the Sun and shorter (or nonexistent) when the comet is farther from the Sun.

What could explain the darker appearance of moons and rings in the outer solar system?

They are made of small, sooty particles and radiation darkening with loss of volatile bright ices.

What is the defining property of the Trojan asteroids?

They have orbits at the distance of Jupiter and 60 degrees ahead of or behind it.

Neptune's large moon ________ is the only large satellite known in a retrograde orbit.

Triton

In terms of axial tilt, which of the jovians shows us the largest inclination?

Uranus

Neptune was discovered as a result of perturbations observed in the orbit of _______.

Uranus

The K-T Boundary Event happened about 65 million years ago when an asteroid the size of Deimos struck the ________ Peninsula.

Yucatan

What is the typical size of most known asteroids?

a few kilometers

The nucleus, or main solid body, of a comet has a typical size of:

a few kilometers.

Large meteoroids are thought to collide with Earth:

a few times in every million-year period.

A day at the north pole of Uranus lasts:

about 42 years

The bright spherical part of a comet observed when it is close to the Sun is the _________.

coma

Small icy bodies in the solar system which travel about the Sun in highly eccentric orbits and come from all directions are ________.

comets

The Apollo and Aten asteroids have orbits that:

cross the orbit of Earth at perihelion.

Uranus was discovered:

less than 250 years ago

Uranus and Neptune both rotate ________ than the Earth does.

faster

The first hint of the role of asteroids in extinction of the dinosaurs came from:

finding a layer of worldwide iridium enriched dust.

A comet entering the inner solar system from afar will __________.

form a coma and some time later form a tail The coma consists of dust and gas released from the comet as it is heated by the Sun. Only later, as the solar wind affects the comet, does material from the coma extend out to form a tail.

Particles ejected from a comet can cause a(n) _______ on Earth.

meteor shower

Which of the following gives direct information about the age of the solar system?

meteorites from asteroidal debris

Pluto's density is most similar to:

moons of the jovian planets.

Uranus' large axial tilt is thought to be the result of:

multiple catastrophic events, such as glancing collisions.

A comet's _______ is the frozen portion of a comet.

nucleus

What part of a comet has only been seen by a space probe?

nucleus

The masses of Neptune and Uranus were first determined by:

observations of the motions of their satellites.

A comet's plasma tail always points directly away from the Sun because __________.

of pressure exerted by the fast-moving charged particles in the solar wind The plasma tail is always directed away from the Sun because it is pushed outward by the solar wind.

Our most detailed knowledge of Uranus and Neptune comes from:

spacecraft exploration.

During the time that a comet passes through the inner solar system, the comet can appear quite bright because __________.

sunlight reflects off the comet's tail and coma Comets are too cool to emit their own visible light, so they shine by reflecting sunlight. The coma and tail can become quite large, and therefore reflect a lot of sunlight.

Iron meteorites are believed to come from:

the core of a dense M-type asteroid, now broken up.

Carbonaceous meteorites are believed to come from:

the crust of a differentiated C type asteroid, now broken up.

Meteor shower debris is believed to come from:

the disintegration of a short period comet over many returns to the Sun.

Based on observations by the Dawn spacecraft, scientists have concluded that Vesta might be:

the only remaining protoplanet in our solar system.

The Oort Cloud is thought to be:

the spherical cloud of comets and some larger icy bodies surrounding the outer solar system.

Neptune and Uranus have a bluish tint because:

their atmospheres contain methane, which absorbs red light.

Meteorites are valuable to astronomers because:

they may provide evidence about the process in which the solar system was born.