Astronomy Ch 8 HW

Astronomers estimate that the age of the Solar System is about ____ years.

4.6 billion

How many planets are there in our Solar System?

8

How did the natural satellites in the Solar System form?

All of these choices are correct. (The moons formed by the accretion of debris from massive collisions, the moons probably formed from planetesimals orbiting the growing planets, the moons likely were "captured" as they wandered too close to the planets)

Which of the following features of the Solar System does the solar nebula hypothesis explain?

All of these choices are correct. (The planets nearest the Sun contain only small amounts of substances that condense at low temperatures, all the planets' orbits lie in nearly the same plane, all the planets orbit the Sun in the same direction)

In our Solar System, an object is called a planet if

All of these choices are correct. (it has cleared its orbital neighborhood, it orbits the sun, it has a spherical shape)

Why was the recent discovery that planets more massive than Jupiter orbit nearby stars in small orbits surprising?

Because according to the nebular hypothesis, massive planets should only form away from their star.

What conclusion can be drawn from the fact that some planets and satellites with solid surfaces have impact craters?

Collisions between Solar System bodies and planetesimals were common at one time.

What are the third, fifth, and seventh planets in order of increasing distance from the Sun?

Earth, Jupiter, Uranus

All of the Solar System's dwarf planets are located in the Kuiper belt.

False

Asteroids are located in the Kuiper belt.

False

Why is Pluto not considered a Jovian planet?

Its mass and radius are very small, and it lacks the thick atmosphere of hydrogen seen on the other Jovian planets.

Imagine that alien astronomers are using the transit method to look for planets around our Sun. Which planet are they most likely to detect first?

Jupiter

Which of the following planets is an outer planet?

Jupiter

Which planets have densities similar to that of the Earth's?

Mars and Mercury

The planet farthest from the Sun is ________.

Neptune

How many stars are there in our Solar System?

One

Which of the following explains the rocky nature of the inner planets?

Only the rocky material could condense at the higher temperatures of the inner part of the Solar nebula.

A spherical region that surrounds the Solar System and extends up to about 100,000 AU from the Sun is called the

Oort cloud

Counting out from the Sun, which planet occupies the position after Jupiter?

Saturn

What is the name of the nebula from which our Solar System was formed?

Solar nebula

Which property of the Solar nebula was the most influential in giving the planets their characteristics?

Temperature

When we see them in the sky, which of the following objects are emitting their own light?

The Sun

A huge interstellar cloud collapsed into a rotating disk with a central bulge. What did this object become?

The disk was the solar nebula and the bulge became the Sun.

Which of the following observations does NOT give astronomers clues about how the Solar System must have formed.

The more distant planets take longer to complete an orbit about the Sun

Based on our understanding of our own solar system, which of the following would be most surprising to observe in an extra solar system of planets?

The planets nearest to the star have a lower density than the planets farther out.

Why are Uranus and Neptune known as ice giants, rather than gas giants?

Their interiors may contain liquid water and other materials that would be ices if not for the hot cores of those planets.

Which of the following is NOT a property of the outer planets?

They all have solid surfaces for spacecraft to land on.

How do scientists estimate the age of the Solar System?

They measure the ratios of radioactive elements in rocks.

As seen from the north celestial pole, the planets orbit the Sun in a counter clockwise direction.

True

The process in which a gas cools and its molecules stick together to form liquid particles is called

condensation.

Comets are _____ while asteroids are _____.

icy; rocky

Which of the following is the strongest evidence in support of the hypothesis that the Solar System was formed by the collapse of a gas and dust nebula?

images of other stars with gas and dust disks surrounding them

According to the nebular hypothesis, which of the following sequences of events are chronologically correct?

interstellar cloud, Solar nebula, accretion, collisions between planetesimals, planets

Pluto is classified as a dwarf planet because

it has not cleared its orbital neighborhood.

What are planetesimals?

large chunks of material (1 mm to several km in size) from which the planets were formed

A planet's average density is equal to its _______ divided by its _______.

mass; volume

Exoplanets are

planets around stars other than the Sun.

Which of the following is NOT a method used by astronomers to detect and study exoplanets?

rotational mapping

Compared to the _____ planets the ______ planets have _____.

terrestrial; Jovian; many satellites

Which of the following Solar System objects has a composition that most resembles the original Solar nebula?

the Jovian planets

What do we call the swarm of comet nuclei in a huge sphere surrounding the Sun and planets?

the Oort cloud

What is gravitational lensing?

the focusing and brightening of starlight by the gravitational field of a foreground star

Measuring the changing light output of a star to search for exoplanets is called ____.

the transit method

The numerous craters we see on the solid surfaces of many Solar System bodies are evidence that ______________________.

they were bombarded in their youth by many solid objects