Our solar system's location in the Milky Way Galaxy

Irregular Galaxy

A Galaxy that does not have the clearly defined shape and structure of typical elliptical, lenticular, or spiral galaxies. Irregular galaxies typically contain large amounts of gas and dust, and their stars are often young.

Spiral Galaxy

A galaxy in which the stars and gas clouds are concentrated mainly in one or more spiral arms.

Galaxy

A system of millions or billions of stars, together with gas and dust, held together by gravitational attraction.

Dark Energy

A theoretical repulsive force that counteracts gravity and causes the universe to expand at an accelerating rate.

Universe

All existing matter and space considered as a whole and that the universe is believed to be at least 10 billion light years in diameter and contains a vast number of galaxies. It has been expanding since its creation in the Big Bang about 13 billion years ago.

Elliptical Galaxy

An approximately ellipsoidal shape and a smooth, nearly featureless brightness profile. Unlike flat spiral galaxies with organization and structure, they are more three-dimensional, without much structure, and their stars are in somewhat random orbits around the center.

Spiral Arm

Are sites of ongoing star formation and are brighter than the surrounding disc because of the young, hot OB stars that inhabit them.

Dark Matter

Nonluminous material that is postulated to exist in space and that could take any of several forms including weakly interacting particles, or high-energy randomly moving particles created soon after the Big Bang.

Big Bang Theory

That the universe may have been created in a huge explosion at least 12 billion years ago.

Milky Way Galaxy

The Milky Way is the Galaxy that contains our solar system. The name Milky is derived from its appearance as a dim glowing band arching across the night sky whose individual stars cannot be distinguished by the naked eye.