Question 1

The presence of dusty disks surrounding stars similar to the Sun was surprising because

Accepted Answer

The presence of dusty disks around stars similar to the Sun was surprising because it was expected that the radiation from a hot star would rapidly eject gas and dust into space, leaving behind little material to form such disks.

Question 2

Comets have been discovered around the star Beta Pictoris through

Accepted Answer

The discovery of comets around Beta Pictoris was made through the detection of emission from gas that evaporates when the comets pass close to the star, indicating their presence.

Question 3

What is the Jeans instability?

Accepted Answer

The Jeans instability refers to a condition in which a cloud of gas and dust becomes sufficiently dense that it begins to collapse under its own gravitational force, potentially leading to the formation of stars and planetary systems.

Question 4

The observation of hot dust around nearby stars implies that those stars have

Accepted Answer

The presence of hot dust around nearby stars suggests that there are collisions between asteroids or other small bodies, which generate dust.

Question 5

The Kepler Space Telescope discovered thousands of exoplanets by measuring

Accepted Answer

The Kepler Space Telescope discovered thousands of exoplanets by measuring the periodic variability in the brightness of stars, which occurs when a planet transits in front of its host star from the perspective of the telescope, causing a temporary dip in the star's brightness.

Question 6

A gas and dust cloud will not necessarily collapse because it normally experiences a balance between its internal gas pressure and

Accepted Answer

A gas and dust cloud's collapse is typically counteracted by its internal gas pressure, which balances against the force of gravity pulling the particles together.

Question 7

Which characteristic MOST directly determines whether a piece of material inside a dense core will eventually become part of the protostar or the protoplanetary disk that surrounds it?

Accepted Answer

The rotational speed of the material in the dense core determines whether it will collapse directly into the protostar or form part of the protoplanetary disk due to angular momentum conservation.

Question 8

Which of these have been detected around nearby stars?

Accepted Answer

All of these objects have been detected around nearby stars. Comets and asteroids are found in other star systems, often inferred through their effects on starlight or from direct imaging. Terrestrial planets have been discovered through various methods such as the transit method, where the planet passes in front of its star from our viewpoint, dimming the star's light slightly, and the radial velocity method, where the gravitational pull of a planet causes its star to wobble slightly.

Question 9

Suppose a dense core forms out of an interstellar cloud that is unusual because it does NOT rotate. How might the resulting protostar differ from the majority of other protostars?

Accepted Answer

Protostars typically form with rotation, which contributes to the formation of a protoplanetary disk around them due to the conservation of angular momentum. A dense core that does not rotate would likely lead to a protostar without a protoplanetary disk, as there is no angular momentum to spread material into a disk shape.

Question 10

What was the first direct evidence that some other solar-type stars might have planets?

Accepted Answer

The answer of What was the first direct evidence that...

Question 11

A gas and dust cloud that is unstable and will collapse is characterized by all of these EXCEPT

Accepted Answer

A gas and dust cloud that is unstable and will collapse is typically characterized by low temperature, low pressure, and high density. These conditions favor the gravitational forces over thermal pressure, leading to collapse. Rapid internal motion, on the other hand, would counteract collapse by providing support against gravity through increased pressure and kinetic energy.

Question 12

MOST protostars are surrounded by

Accepted Answer

Most protostars are surrounded by disks of gas and dust. These disks are a natural part of the star formation process, as the material in the surrounding molecular cloud collapses under gravity to form the protostar and its disk.

Question 13

In astronomy, a dense core is a region in the process of forming a

Accepted Answer

Dense cores are regions within molecular clouds where stars are in the process of forming. These areas have higher densities and are the initial stages of star formation.

Question 14

Young stars are sometimes observed to have multiple debris disks inclined relative to each other. This phenomenon is a result of

Accepted Answer

The gravitational influence of massive planets in the system can cause the formation of multiple debris disks inclined relative to each other around young stars. These planets can perturb the orbits of smaller bodies and dust, leading to the creation of debris disks at different inclinations.

Question 15

Strong evidence for the existence of planetary systems in the process of formation around other stars comes from

Accepted Answer

Images and infrared observations of disks of dust around young stars are considered strong evidence for the existence of planetary systems in the process of formation. These disks, often called protoplanetary disks or circumstellar disks, are regions where planets can form from the accretion of dust and gas.

Question 16

An asteroid belt has been discovered around the star Zeta Leporis. How was this belt discovered?

Accepted Answer

The discovery of a ring of hot dust around the star Zeta Leporis through spectroscopy, and the inference that collisions among asteroids are the cause, indicates the presence of an asteroid belt. This method does not rely on direct imaging or observing gravitational effects on the star itself, but rather on the detection of dust produced by collisions within the belt.

Question 17

An astronomer discovers a protoplanetary disk with spiral waves. This may be evidence for

Accepted Answer

Spiral waves in a protoplanetary disk are often considered evidence for planets forming within the disk. These waves can be caused by the gravitational influence of a planet on the disk material, leading to the formation of spiral structures.

Question 18

Asteroids have been detected around nearby stars through

Accepted Answer

Asteroids around nearby stars are often detected by observing the infrared emission from hot dust, which is generated by collisions among the asteroids. This dust emits heat that can be detected as excess infrared radiation.

Question 19

An astronomer is trying to detect an exoplanet via the transit method. Which of these changes to a particular planet will make it EASIER to detect, if everything else about the planet is unchanged?

Accepted Answer

Increasing the radius of an exoplanet makes it easier to detect via the transit method because a larger planet blocks more of its star's light when it passes in front of the star, creating a more noticeable dip in the star's brightness.

Question 20

Astronomers have searched for extrasolar planets for decades. Which one of these statements about the current status of the search is NOT true?

Accepted Answer

Astronomers have discovered thousands of extrasolar planets, or exoplanets, indicating that planets beyond our solar system do indeed exist. This makes statement A incorrect.

Quiz 5: Exoplanets and the Formation of Planetary Systems