Stars are mostly made of

• hydrogen and helium

• pure hydrogen

• carbon, hydrogen, oxygen and nitrogen

• an equal mixture of all elements

Compared to young stars, very old stars have

• exactly the same chemical composition

• a lower proportion of elements heavier than helium

• a higher proportion of elements heavier than helium

• no elements heavier than helium at all

The presence of elements heavier than helium in stars is very important because

• they provide the raw materials for the formation of planets and life

• without them they could not form

• they help stabilize their interiors

• they are responsible for the fusion reactions at their centers

Stars spend most of their lives

• fusing hydrogen into helium in their cores

• slowly dimming as they die with no fusion occurring in their cores

• as slowly brightening protostars

• fusing helium into carbon in their cores

The most important property of a star which determines its evolution is its

• chemical composition

• surface temperature

• mass

• radius

What is the minimum possible mass for a star?

• 0.01 solar masses

• 0.008 solar masses

• 0.1 solar masses

• 0.08 solar masses

The color of a star is a measure of its

• surface temperature

• chemical composition

• mass

• size

The intrinsic brightness of a star is referred to as its

• radiance

• luminosity

• surface temperature

• apparent brightness

One of the fundamental principles of stellar evolution is that the more massive a star is

• the more heavy elements it contains

• the more planets it has around it

• the faster it evolves

• the slower it evolves

A star less massive than our Sun

• will have a longer lifetime

• will have a shorter lifetime

• will have the same lifetime as the Sun

• could have either a longer lifetime or a shorter lifetime depending on its chemical composition