Space and H-R Diagrams

Universe

All of space and the matter it contains.

Galaxy

An extremely large group of stars in space.

Irregular Galaxy

Blob-shaped young galaxy filled with young stars.

Spiral Galaxy

Flat disc-shaped middle-aged galaxy with spiral arms.

Elliptical Galaxy

Oval or egg-shaped old galaxy filled with old stars.

Nebula

Large cloud of gas and dust where stars form.

Protostar

Earliest stage of star formation before light emission begins.

Star

Superheated gas, producing light through nuclear reactions.

Luminosity (on the HR Diagram)

The measure of how bright a star is.

Apparent Luminosity

How bright a star appears when viewed from Earth.

Absolute Luminosity

The true brightness of a star.

H-R Diagram

Diagram categorizing stars by surface temperature and luminosity.

Main Sequence Star

Stable, middle-aged stars along the H-R diagram's diagonal belt.

Giant Star

Large, older star that is bright but cool.

Supergiant Star

Extremely large, extremely bright, but cooler older star.

White Dwarf Star

Small, very old star that is dim but hot.

Supernova

The explosive death of a massive star.

Black Hole

Intense gravity region formed by a collapsed massive star.

Surface temperature of Star

Affects the color of a star

Coolest Star Color

Red

Hottest Star Color

Blue

Neutron Star

Extremely dense collapsed core of a massive star after a supernova.