Question 1

Explain the nebular hypothesis, and describe two observations that support it.

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Question 2

Hot Jupiters were the first exoplanets to be discovered, and have since been found to be

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Question 3

What is the habitable zone?

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The habitable zone is defined as the region around a star where conditions are right for liquid water to exist on a planet's surface, which is crucial for life as we know it.

Question 4

Why does an accretion disk heat up?

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Question 5

If an astronomer on a planet orbiting a nearby star observed the Sun when Neptune was transiting in front of the Sun, how would the Sun's brightness change? Note that the radius of Neptune is 2.5 * 10⁷ m.

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When Neptune transits in front of the Sun, it blocks a small fraction of the Sun's light, causing a slight decrease in brightness. Given Neptune's size relative to the Sun, the decrease would be around 0.1 percent.

Question 6

What evidence do we have that the accretion disk that formed the Solar System was initially much denser near its center?

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Question 7

Compare the orbital angular momentum of Earth and Jupiter.Which is larger and by how much? (Note that Jupiter's mass is 318 times that of Earth, the semimajor axis of Jupiter's orbit is 5.2 AU, and Jupiter's orbital period is 12 years.)

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Question 8

If you detect an exoplanet that is orbiting a star that is 8 times as massive as the Sun with an orbital period of 1 (Earth) year, you would expect the semimajor axis of its orbit to be

Accepted Answer

According to Kepler's third law, the square of the orbital period (T) is proportional to the cube of the semimajor axis (a) divided by the mass of the star (M). For a star 8 times the mass of the Sun, the semimajor axis a = (T^2 * M)^(1/3) = (1^2 * 8)^(1/3) = 2 AU.

Question 9

Explain why an accretion disk forms around a protostar when an interstellar cloud collapses.

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Question 10

Explain the primary reasons why the inner solar nebula was hotter than the outer solar nebula.

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Question 11

What happens to the rotation speed of a slowly rotating cloud as it collapses to form a stellar system? Why does this occur?

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Question 12

The borderline between the most massive planet and the least massive brown dwarf is thought to occur at around

Accepted Answer

The borderline between the most massive planet and the least massive brown dwarf is generally considered to be around 13 Jupiter masses, as this is the mass at which deuterium fusion can occur, a characteristic of brown dwarfs.

Question 13

Explain why astronomers believe that the formation of planets is a natural by-product of star formation.

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Question 14

Astronomers believe that the "hot Jupiters" found orbiting other stars must have migrated inward over time

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Hot Jupiters are thought to migrate inward by losing orbital angular momentum, often due to interactions with the protoplanetary disk or other planets, causing them to spiral closer to their host star.

Question 15

The figure shown below illustrates the changing brightness of a star due to a planet transiting in front of it.Which of the following can be directly measured from the information provided?

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Question 16

What does conservation of angular momentum mean?

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Question 17

How do meteorites tell us about how the solar system formed?

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Question 18

When astronomers began searching for extrasolar planets, they were surprised to discover Jupiter-sized planets much closer than 1 AU from their parent stars.Why is this surprising?

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Astronomers were surprised because gas giants like Jupiter are expected to form in the cooler, outer regions of a solar system and then migrate inward, which was initially thought to be a rare occurrence.

Question 19

As the radius, r, of extrasolar planets increases, we expect the amount of light they block from their parent star to change by a factor of ________.

Accepted Answer

The amount of light blocked by a planet during a transit is proportional to the area of the planet's disk, which is πr². Therefore, as the radius increases, the amount of light blocked increases by a factor of r².

Question 20

Astronomers have discovered other stars with planets that are more massive than Earth, but less massive than Neptune, that are called

Accepted Answer

These planets are called super-Earths or mini-Neptunes because they are larger than Earth but smaller than Neptune.

Quiz 7: The Formation of Planetary Systems