The word galaxy derives from the Greek term for our own galaxy, galaxias (γαλαξίας), or kyklos galaktikos, meaning "milky circle" for its appearance in the sky.
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A galaxy is a vast self-gravitating structure of interstellar matter, energy, and forces.
A galaxy is a gravitationally-bound region of space consisting of luminous and dark matter as a single physical system.
An Irregular Galaxy is a galaxy that has no shape or form as defined by the classes of the "Hubble sequence" An Amorphous galaxy is a galaxy that has neither spiral nor elliptical in shape as defined by "The Atlas of Peculiar Galaxies". See related links for pictorial representation
A galaxy. We live in one corner of a galaxy that we have named the "Milky Way" galaxy. It is thought to contain anywhere from 200 to perhaps 400 billion stars. The grouping of billions of stars, gas, and dust into a physically metastable rotating state by gravity is, by definition, a galaxy.
Somewhere between 200 and 400 billion, depending upon how you define "sun." If you define it as a star, then see above. If you omit neutron stars and various dwarf stars or proto suns (stars which have not yet begun nuclear fusion), there would be less. If you define as sun as any star with one or more planets in orbit, we only know of 623+ so far, though again the number would likely be in the billions.
It's difficult to define a galaxies size, as there is no real cut off point. From estimations, the Andromeda is about twice as large as the Milky Way.
I think it is very difficult to define size to a galaxy, as there is not real cut off point. Recent observations showed a "halo" of Stars around the Galaxy - a bit like suburbs to a city. Putting the size to 500,000 light years across. Current thoughts are that it is twice the size of our own Galaxy, so around 200,000 light years across. Maybe someone else can contribute a more recent guesstimate.
Our galaxy is a barred spiral galaxy.
The Andromeda Galaxy is a spiral galaxy.
Our galaxy is a spiral galaxy because it is spiral in shape.
Not counting the Magellanic Clouds (which are minielliptical galaxies orbiting our galaxy), the Andromeda galaxy is the galaxy nearest to our galaxy.
No, a tadpole galaxy is not a type of peculiar galaxy. It is a barred spiral galaxy.