What is a galaxy ?

Answer 1

Any of numerous large-scale aggregates of stars, gas, and dust that constitute the universe, containing an average of 100 billion (1011) solar masses and ranging in diameter from 1,500 to 300,000 light-years. Also called nebula
often Galaxy. The Milky Way.
An assembly of brilliant, glamorous, or distinguished persons or things: a galaxy of theatrical performers.

Answer 2

A Galaxy is a large band of stars ,gas and dust particles held together by gravitaional forces. Galaxies are really complex organisations consisting of millions and millions of stars.There are also galaxies observed with no gas and dust.The milky way is our galaxy.Stellar systems like our Milky way form the major building block of the universe.

Answer 3

A galaxy (from the Greek root γαλαξίας, meaning "milky", a reference to our own Milky Way) is a massive, gravitationally bound system consisting of stars, an interstellar medium of gas and dust, and dark matter. Typical galaxies range from dwarfs with as few as ten million (107) stars up to giants with one trillion (1012) stars, all orbiting a common center of mass. Galaxies can also contain many multiple star systems, star clusters, and various interstellar clouds.

Historically, galaxies have been categorized according to their apparent shape (usually referred to as their visual morphology). A common form is the elliptical galaxy, which has an ellipse-shaped light profile. Spiral galaxies are disk-shaped assemblages with curving, dusty arms. Galaxies with irregular or unusual shapes are known as peculiar galaxies, and typically result from disruption by the gravitational pull of neighboring galaxies. Such interactions between nearby galaxies, which may ultimately result in galaxies merging, may induce episodes of significantly increased star formation, producing what is called a starburst galaxy. Small galaxies that lack a coherent structure could also be referred to as irregular galaxies.

There are probably more than one hundred billion (1011) galaxies in the observable universe. Most galaxies are 1,000 to 100,000[4] parsecs in diameter and are usually separated by distances on the order of millions of parsecs (or megaparsecs). Intergalactic space (the space between galaxies) is filled with a tenuous gas of an average density less than one atom per cubic metre. The majority of galaxies are organized into a hierarchy of associations called clusters, which, in turn, can form larger groups called superclusters. These larger structures are generally arranged into sheets and filaments, which surround immense voids in the universe.

Although it is not yet well understood, dark matter appears to account for around 90% of the mass of most galaxies. Observational data suggests that supermassive black holes may exist at the center of many, if not all, galaxies. They are proposed to be the primary cause of active galactic nuclei found at the core of some galaxies. The Milky Way galaxy, home of Earth and the solar system, appears to harbor at least one such object within its nucleus.

Answer 4

galaxies are large systems of stars and interstellar matter, typically containing several million to some trillion stars, of masses between several million and several trillion times that of our sun, of an extension of a few thousands to several 100,000s light years, typically separated by millions of light years distance. they come in a variety of flavors: spiral,lenticular, elliptical, irregular...........milky way galaxy is the giant spiral galaxy

Answer 5

A galaxy is a big house for stars, nebulas and clusters Which goes on changing its shape...
This is a galaxy:
http://www.le.ac.uk/physics/faulkes/web/images/galaxies.jpg


Many galaxies together make a galaxy cluster.
In the center of a galaxy,There is a huge bludge of gas, stars. etc.

first of all, a galaxy is like this: elliptical galaxy:
http://www.galex.caltech.edu/IMAGES/elliptical-m87.gif

Then it showly becomes: spiral galaxy
http://geology.com/news/images/spiral-galaxy.jpg

Or it becomes: seyfert galaxy
http://amazing-space.stsci.edu/resources/explorations/hdf/images/NGC1566-l.jpg

This is also one type of galaxy: irregular galaxy
http://www.ast.cam.ac.uk/~jmi/images/wlm.jpg

Overall galaxy evolution:
http://bdaugherty.tripod.com/gcseAstronomy/images/HubbleClassification.jpg

All about galaxies:
http://en.wikipedia.org/wiki/Galaxy



But this is taught in high schools...

Answer 6

A galaxy is, by definition, any large collection of stars that can be recognized as a distinct physical entity

Answer 7

A large system of stars held together by mutual gravitation and isolated from similar systems by vast regions of space.

Answer 8

A galaxy (from the Greek root γαλαξίας, meaning "milky", a reference to our own Milky Way) is a massive, gravitationally bound system consisting of stars, an interstellar medium of gas and dust, and dark matter.

Answer 9

A very large system consiting of stars bound togather by gravitational force.

Answer 10

Cluster of stars held together by the same solar system,.