astronomy questions?

Question

What is the difference between a star cluster and a galaxy?
Is there a relationship between size and temperature? If so, what?
Compare and contrast elliptical and spiral galaxies.

Answer 1

Galaxies contain billions of stars, including star clusters. Star clusters are groups of stars that are gravitationally attracted. There are two types of star clusters; open star clusters, and globular star clusters. Globular star clusters are well organized, and composed mostly of older stars. Stars in globular clusters have a very strong gravitational attraction, giving these clusters a round, globular appearance, hence the name. These clusters reside towards the center of our own galaxy and other spirals, and are the main type of cluster found in elliptical galaxies. More on that in a minute.
Open star clusters are less organized, and composed of younger stars and sometimes surrounding nebulosity where stars are forming, such as the Pliades star cluster in Taurus. These stars are often hot, massive, and blue-white in color. The gravitational attraction is weaker in these clusters, and it is not uncommon for a star to "escape" the cluster. These clusters form in the arms of spiral galaxies.
Spiral galaxies resemle our own Milky Way and have spiral arms that resemble pinwheels. Spirals have a surrounding disk usually composed of younger and main sequence stars, and open star clusters. Because of these clusters, spiral arms often appear to be blue in color. Spirals also have more dust and gas and interstellar matter, allowing for the posibility of continued stellar formation. Our own solar system resides in a spiral arm of the Milky Way. When you look at the Milky Way, you are looking at a spiral arm. If you want to look towards the center, look towards Saggitarius in the summer months, but you will not be able to see the center. Dark clouds of dust and gas obscure our view.
Ellipticals, on the other hand, have no surrounding disk, and are composed of older, globular star clusters. There is very little interstellar dust and gas, so there is no or very little stellar formation in these galaxies.
Other types of galaxies include barred spirals, lenticular, and irregulars.

Answer 2

Homework question?

You should probably break these questions up.

A star cluster is going to be smaller and have a different structure from a galaxy (galaxies have the nucleus, buldge, disk and halo). I would think that being less massive the dynamics of a star cluster are also different... I don't think they'd spin like galaxies. I do not know about tempurature, you'll have to read for that... I'd think that since galaxies are larger, more mobile and have that active center with a possible black hole that they would have a higher tempurature. The only difference I know about with elliptical and spiral galaxies is their shape, a spiral has arms and is, I believe, typically more flattened out in the disk.


EDIT: A star cluster can include planets.

Answer 3

Star clusters are clusters of just stars while galxy includes lots of materials= planets, asteroids, comets...blah. blah..

I only know something about spiral galzy.

spiral galaxy is designed like a hurricane. It goes round and round. Really cool. the stars form like a path to the center.

Hope that helped!

Answer 4

star clusters are just that. Galaxies however include planets.