Irregular galaxies are without a spiral or Elliptical shape. They tend to be smaller objects that are without definite shape and tend to have very hot newer stars mixed in with lots of gas and dust.

Spiral Galaxies-have a bulge at the center and a flattened disk containing spiral arms. Spiral galaxies have a verity of shapes and are classified according to the size of the bulge and especially the tightness of the arms. The spiral arms wrap around the bulge and contain mostly young blue stars. Spiral galaxies turn like a Frisbee or a hurricane.

What Is A Galaxy?

A galaxy is an enormous collection of billions of stars, gas, and dust held together by gravity. One galaxy can have hundreds of billions of stars and be as much as 200,000 light years across.

Parts Of A Galaxy

Bulge- the bulge is a round structure made of stars, gas, and dust. The bulge part of the Milky Way is 30,000 light years across.

Disk- the disk is a flattened region that surrounds the bulge in a spiral galaxy. The disk is shaped like a pancake. It is 100,000 light years across and 2,000 light years thick. It contains mostly young stars, air, and dust, which are concentrated in spiral arms. Some old stars are also present.

Spiral arms- The Spiral arms are curved extensions beginning at the bulge of a spiral galaxy, giving it a "pinwheel" appearance. Spiral arms contain as much gas and dust as young blue stars. Spiral arms are found only in spiral galaxies.

Halo- the Halo contains clusters of old stars {"globular clusters"}, individual old stars, gas, and dust. It may be 130,000 light years across The Halo also contains a dark side, which is material that we know exists, but cannot see.

Stars, Gas, And Dust- Stars come in a verity of types. Blue stars are very hot and young. Old stars are cooler and red. Spiral galaxies seem to have a lot of gas and dust. Other galaxies like elliptical galaxies have very little gas or dust.

Spiral galaxies- have a bulge at the center and a flattened disk with spiral arms. Spiral galaxies have a variety of shapes and are classified according to the size of the bulge and the tightness of the appearance of the arms. The spiral arms wrap around the bulge and contain mostly young blue stars and lots of gas and dust. Older red stars are usually stationed in the bulge. Yellow stars like our sun are mid-life stars and are also found in the spiral arms. These galaxies are somewhat like spinning Frisbees or hurricane’s.

Barred spiral galaxies- these spiral galaxies are spirals that have a bar running across the center of the galaxy.

Elliptical galaxies- elliptical galaxies do not have a disk or arms. Instead they are characterized by a smooth, ball- shaped appearance. Elliptical contains old stars and possesses little gas or dust. They are classified by the shape of the ball which can range from round to oval. In contrast to spirals, elliptical do not rotate. The stars move within the galaxy like a swarm of bees.

Irregular galaxies- are without a spiral or elliptical shape. They tend to have smaller objects that are without definite shape and tend to have very hot newer stars that mix in with lots of gas and dust.

[Acknowledgements] [About Us] [Contact Us] [Contents] [Solar System] [Constellations] [Galaxies] [Exploration] [Home]