Nebulas, Galaxies, and Dark Matter

Elliptical Galaxies

Elliptically-shaped galaxies with less gas and dust than spirals, and no disk or 'arms'.

Nebulas

Clouds of gas and dust inside galaxies, closely associated with stellar birth and death.

Harlow Shapley

Discovered that we are not in the center of the galaxy, but about 26,000 light years from the center on one of the spiral arms.

Barred Spiral Galaxies

Similar to spirals but with a bright bar of stars and gas through the center.

Peculiar Galaxies

Distorted forms of other galaxy types, often due to collision with another galaxy or similar catastrophic event.

Dark Matter

Unseen matter that does not interact with light, providing the structure for the visible universe.

Gravitational Lensing

Method to detect Dark Matter's presence through the bending of light.

Dark Energy

Mysterious force believed to be accelerating the expansion of the universe.

Hydrogen

Element whose depletion is believed to lead to the universe going dark and freezing.

Reflection Nebula

Nebula that reflects the light of nearby stars.

Absorption Nebula

Nebula that obscures our view and appears as a silhouette against a bright background.

Dark Nebula

A dense nebula that blocks the light from background stars.

Edwin Hubble

Discovered that some nebulae were composed of stars and that the universe was composed of more than just the Milky Way.

Hubble's Law

Implication that the universe is expanding, with the rate of expansion accelerating.

Hubble Deep Field

An image taken in the constellation Ursa Major, revealing numerous galaxies.

Milky Way Galaxy (MWG)

Our home galaxy, a spiral galaxy about 100,000 light years across.

Density Wave

Mechanism that may have created the spiral arms by 'piling up' material in the Milky Way Galaxy.

Interstellar medium

The gas and dust between the stars.

Andromeda Galaxy

Our closest galactic neighbor, with which the Milky Way will eventually collide.

Supermassive Black Hole

A black hole at the center of our galaxy, and many others, with immense mass.

Spiral Galaxies

Galaxies with a disk-like appearance and arms of stars and dust forming a spiral pattern.

Irregular Galaxies

Galaxies neither elliptical nor spiral in shape, with gas and dust as in spirals but no defined 'arms'.