What is a Galaxy and, how many different kinds are there

Joson Anjo C. CasillanVII- Amorsolo

What is a galaxy

• Massive• Gravitationally bound• Stars• Stellar remnants• Dust and dark matter

Stellar Remnants

• White dwarfs• Neutron stars• Other exotic dense stars• Black holes

Stellar evolution

• The cycle of stars• Stellar evolution is the process by which a star

undergoes a sequence of radical changes during its lifetime.

How many different kinds of galaxy are there

• Elliptical• Spiral• Barred spiral• Irregular• Peculiar

Elliptical

• An elliptical galaxy is a type of galaxy having an approximately ellipsoidal shape and a smooth, nearly featureless brightness profile.

Spiral• Spiral galaxies consist of a flat,

rotating disc containing stars, gas and dust, and a central concentration of stars known as the bulge. These are surrounded by a much fainter halo of stars, many of which reside in globular clusters.

Barred spiral

• A barred spiral galaxy is a spiral galaxy with a central bar-shaped structure composed of stars. Bars are found in approximately two-thirds of all spiral galaxies.

Irregular

• An irregular galaxy is a galaxy that does not have a distinct regular shape, unlike a spiral or an elliptical galaxy.

Peculiar

• A peculiar galaxy is a galaxy which is unusual in its size, shape, or composition.

References

• http://www.apodnasa.gov• http://www.newscientist.com• http://ibp.fieldofscience.com• http://en.wikipedia.com