Galaxies are generally not isolated in space but are often members of small or moderate sized groups,which in turn forn large clusters of galaxies.We are in the so called Local Group along with about 20 others.The earth's galaxy and our neighbor Andromeda galaxy are the two largest members,having at least a million million stars.The largest known galaxy has about 13 times as many stars as the Milky Way .Email me if you its name. basic_astronomy@yahoo.com

Besides stars and planets,galaxies contain clusters of stars,atomic hydrogen gas,molecular hydrogen,molecules composed of hydrogen,nitrogen,carbon,silicon,cosmic rays,and others..

Here are some additional pictures of galaxies.

M31 is the famous Andromeda galaxy, our nearest large neighbor galaxy, forming the Local Group of galaxies together with its companions (including M32 and M110, two bright dwarf elliptical galaxies), our Milky Way and its companions, M33, and others.

Visible to the naked eye even under moderate conditions, this object was known as the "little cloud" to the Persian astronomer Al-Sufi, who observed it as early as 905 AD (described 964 AD in his Book of Fixed Stars). Charles Messier was obviously unaware of this early report and ascribed its discovery to Simon Marius, who was the first to give a telescopic description in 1612. Unaware of both Al Sufi's and Marius' discovery, Giovanni Batista Hodierna independently rediscovered this object before 1654.

It was longly believed that the "Great Andromeda Nebula" was one of the closest nebulae. William Herschel believed, wrongly of course, that its distance would "not exceed 2000 times the distance of Sirius" (17,000 light years); nevertheless, he viewed it at the nearest "island universe" like our Milky Way which he assumed to be a disk of 850 times the distance of Sirius in diameter, and of a thickness of 155 times that distance.

It was William Huggins, the pioneer of spectroscopy, who noted the difference between gaseous nebula with their line spectra and those "nebulae" with continuous spectra, which we now know as galaxies.

At modern times, the Andromeda galaxy is certainly the most studied "external" galaxy. It is of particular interest because it allows studies of all the features of a galaxy from outside which we also find in Milky Way, but cannot observe as the greatest part of our Galaxy is hidden by interstellar dust. Thus there are continuous studies of the spiral structure, globular and open clusters, interstellar matter, planetary nebulae, supernova remnants, galactic nucleus, companion galaxies, and more.

The brightest of the more than 300 globular clusters of the Andromeda Galaxy M31, G1, is also the most luminous globular in the Local Group of Galaxies; its apparent visual brightness from Earth is still about 13.72 magnitudes. It outshines even the brightest globular in our Milky Way, Omega Centauri, and can be glimpsed even by better equipped amateurs under very favorable conditions, with telescopes starting at 10-inch aperture The Hubble Space Telescope was used to investigate globular cluster G1 in mid-1994 (published April 1996).

The brightest star cloud in the Andromeda galaxy M31 has been assigned an own NGC number: NGC 206, because William Herschel had taken it into his catalog as H V.36. It is the bright star cloud at the upper left, just below a conspicuous dark nebula.

The galaxy M100 (100th object in the Messier Catalog of non-stellar objects) is one of the brightest members of the Virgo Cluster of galaxies. The galaxy is in the spring constellation Coma Berenices and can be seen through a moderate-sized amateur telescope. M100 is spiral shaped, like our Milky Way, and tilted nearly face-on as seen from earth. The galaxy has two prominent arms of bright stars and several fainter arms. Though the galaxy is estimated to be tens of millions of light-years away, Hubble reveals the sort of detail only seen previously (with ground based telescopes) in neighboring galaxies that are ten times closer. Before HST, astronomers could only see such a level of detail in roughly a dozen galaxies in our Local Group. Now, with Hubble's improved vision, the portion of the universe which can be studied with such clarity has grown a thousand fold. Only the future will tell what revelations await as Hubble's spectacular vision is applied to a host of fascinating and important questions about the universe and our place in it.

M61:

Virgo Spiral Galaxy

Explanation: M61 is a barred spiral galaxy located in the nearby Virgo Cluster of Galaxies. Visible in M61 are a host of features common to spiral galaxies: bright spiral arms, a central bar, dust lanes, and bright knots of stars. M61, also known as NGC 4303, in similar to our own Milky Way Galaxy. M61 was discovered by telescope in 1779 twice on the same day, but one observer initially mistook the galaxy for a comet. Light from M61 takes about 60 million years to reach us. Recent observations of M61 have detected unpredicted high velocity gas moving in its halo.

M33 is a prominent nearby spiral galaxy. Nicknamed the Triangulum, M33 is one of the larger members of the Local Group of Galaxies. Two massive spiral galaxies dominate the Local Group: M31 and our Milky Way Galaxy. M33 is the only other spiral galaxy known in the Local Group. At 3 million light-years, M33 is the second closest spiral galaxy. M33 is thought by some to be a satellite galaxy to massive M31. M33 is close enough to appear twice the angular size of the full moon, when viewed with binoculars. Globular clusters in M33's halo appear unusual and might be much younger than globular clusters in our Galaxy's halo.