Universe, Galaxies, and Stars

Big Bang Theory

the theory that the universe originated due to an explosion of small mass of matter at extremely high density and temperature

Cosmic Background Radiation

The electromagnetic radiation left over from the big bang

Temperature (Big Bang)

Evidence that states there is still heat in the universe left over from the Big Bang

Expanding Universe

the idea that the space between galaxies or clusters of galaxies is growing with time.

Open Universe

It is believed that the universe will continue to expand forever.

Closed Universe

The theory that the universe will continue to expand so much that it runs out of momentum and collapses on itself

Flat Universe

The theory that the universe will reach a size and stay that size

Dark Matter

matter that does not give off electromagnetic radiation but is quite abundant in the universe

Dark Energy

a mysterious force that appears to be causing the expansion of the universe to accelerate

Galaxy

A large collection of planets and stars held together by gravity

Elliptical Galaxy

A galaxy shaped like a round or flattened ball, generally containing only old stars

An oval-shaped galaxy that contains mainly older stars, a few new stars, and very little gas and dust.

Lenticular Galaxy

Central buldge, no spiral arms

Spiral Galaxy

a galaxy with a bulge in the middle and arms that spiral outward in a pinwheel pattern

Local Group

A small group of two dozen galaxies

Galaxy Supercluster

Huge swarm of galaxies

Active Galaxy

a galaxy with an unusually luminous nucleus

Quasar

distant yet high energy astronomical object

Milky Way

our galaxy, has trillions of stars

Spiral Arms

The curved swirling regions of a spiral galaxy where stars, gas, and dust are more concentrated.

Binary Stars

Star systems that have two stars

Constellations

Imaginary patterns of stars in the sky.

Parallax

The shift of an object when viewed from different positions

Light Year

Distance light travels in one year.

Parsec

3.26 light years

Doppler Shift

the shift to a different wavelength on the electromagnetic spectrum (when light source is moving away it is red shifted and when light source is moving closer it is blue shifted)

Star Magnitude

The brightness of a star on a scale of -8 to +17.

Apparent Magnitude

The brightness of a star when viewed from Earth

Absolute Magnitude

how bright a star actually is

Hydrostatic Equilibrium

the balance of the inward gravitational force and the outward force of fusion within a star. This balance of forces is what keeps a main sequence star stable.

Nebula

A large cloud of dust and gas in space

Protostar

A cloud of gas and dust in the shape of the star, but without nuclear fusion

Average Mass Star

What is a main sequence star

Red Giant

A star that expands and cools once it runs out of hydrogen fuel

Planetary Nebula

A huge cloud of gas that is created when the outer layers of a red giant star drift out into space

White Dwarf

A small, hot, dim star that is the leftover center of an old star

Black Dwarf

A white dwarf but dark and cool

Nuclear Fusion

The process of hydrogen turning into helium and releasing energy

Red Supergiant

Red giant increases in size and brightness

Supernova

a star that suddenly increases greatly in brightness that ejects most of its mass.

Neutron Star

a star that is made of electrons and protons smashed together, they form neutrons

Black Hole

An object in space whose gravity is so strong light cant escape