Chapter 14

Question 1

Habitable Zone

Answer 1

The distance from a host star where a planet can sustain liquid water on its surface.

Question 2

Main Sequence

Answer 2

The period during which a star burns hydrogen in its core (high mass star stay on the main sequence for ~1 million years, while low-mass stars stay on the main sequence for ~1 trilion years).

Question 3

Mass-Luminosity Relationship

Answer 3

A more massive star is more luminous (L~M^4)

Question 4

Calculation for the Lifetime of a Star

Answer 4

t = M/L = 1/M^3

t = Time
M = Stellar Mass
L = Luminosity

Question 5

Tidally Locked

Answer 5

Exhibiting synchronous rotation - can happen for a small body orbiting close to a large body (like the Earth and Moon system)

Question 6

Free-floating Planets

Answer 6

A planet that has been ejected from its solar system. Could potentially host life if the planet was able to hold on to a thick hydrogen atmosphere. Would be difficult to detect.

Question 7

Stable Planetary Orbit

Answer 7

Circular, unchanging. For example, a stable around a tight binary system would need to be far from the binary. A stable orbit around a wide binary system would need to be close to one of the stars.

Question 8

Galactic Habitable Zone

Answer 8

The distance from the center of the galaxy where life could arise. Too close, and you’re in danger from the supermassive black hole at the center of the galaxy (as well as erupting supernovae). Too far away, and you don’t have the heavy materials (metals) needed to form rocky planets. You also need to be near the co-rotation radius of the galaxy.

Question 9

Co-rotation Radius

Answer 9

A special distance from the center of the galaxy where stars orbit the center of the galaxy as one group (without moving relative to one another). This is an area with fewer supernovae, and a safe place for life to arise.