Astronomy Stars and Stellar Evolution 2

Question 1

What is the primary source of energy in a main-sequence star like the Sun?

Accepted Answer

Nuclear fusion of hydrogen into helium

Answer

Main-sequence stars fuse hydrogen into helium in their cores, releasing enormous energy.

Question 2

Which property of a star determines its position on the main sequence?

Accepted Answer

Its mass

Answer

A star's mass sets its temperature and luminosity, fixing its position on the main sequence.

Question 3

What color are the hottest stars?

Accepted Answer

Blue

Answer

Blue stars have the highest surface temperatures, often exceeding 25,000 K.

Question 4

The Hertzsprung-Russell diagram plots luminosity against which stellar property?

Accepted Answer

Surface temperature

Answer

The H-R diagram plots luminosity versus surface temperature (or spectral class).

Question 5

What happens to a Sun-like star when it exhausts hydrogen in its core?

Accepted Answer

It expands into a red giant

Answer

Core hydrogen exhaustion causes the outer layers to expand and cool into a red giant.

Astronomy Practice Test