The composition of a star can e identified by

• the size of the star

• the lines in its spectrum

• its apparent brightness

• the intensity of its radiation

Supergiant stars

• form supernovas

• fuse hydrogen into carbon

• form from red giants

• form planetary nebulae

The universe is made up of mostly

• interstellar matter

• empty space

• dark matter

• stars

The brightness of a star depends on its

• distance from Earth

• temperature

• size

• all of the above

Astronomers estimate that the universe contains

• 100 galaxies

• 100 trillion galaxies

• 100 billion galaxies

• 100 million galaxies

Stars are held together by

• ionic forces

• magnetic forces

• gravitational forces

• electrical forces

A _____ is so massive and compressed that not even light can escape its gravity.

• supernova

• protostar

• black hole

• neutron star

Who first proposed that the universe is expanding?

• Hubble

• Kepler

• Darwin

• Copernicus

All stars radiate

• heat energy

• light energy

• electromagnetic waves

• all of the above

The core is the hottest part of the sun with a temperature of about

• 15,000,000 K

• 1,000,000 K

• 50,000 K

• 200,000,000 K