Andromeda Galaxy

==Overview==
The Andromeda Galaxy is a barred spiral galaxy and is the nearest major galaxy to the Milky Way, where the Solar System resides. It was originally named the Andromeda Nebula and is cataloged as Messier 31, M31, and NGC 224,(In version 0.990, the Andromeda galaxy has the code 1236). Andromeda has a diameter of about 46.56 kiloparsecs or 152,000 light-years (141,520 light-years in Space Engine) and is approximately 765 kpc (2.5 million light-years) from Earth. The galaxy's name stems from the area of Earth's sky in which it appears, the constellation of Andromeda
==Nearby and satellite galaxies==
Like the Milky Way, the Andromeda Galaxy has satellite galaxies, consisting of over 20 known dwarf galaxies. The Andromeda Galaxy's dwarf galaxy population is very similar to the Milky Way's, but the galaxies are much more numerous. The best known and most readily observed satellite galaxies are M32 and M110. Based on current evidence, it appears that M32 underwent a close encounter with the Andromeda Galaxy in the past. M32 may once have been a larger galaxy that had its stellar disk removed by M31 and underwent a sharp increase of star formation in the core region, which lasted until the relatively recent past.
M110 also appears to be interacting with the Andromeda Galaxy, and astronomers have found in the halo of the latter a stream of metal-rich stars that appear to have been stripped from these satellite galaxies. M110 does contain a dusty lane, which may indicate recent or ongoing star formation. M32 has a young stellar population as well.
The Triangulum Galaxy is a non-dwarf galaxy that lies 750,000 light years from Andromeda. It is currently unknown whether it is a satellite of Andromeda.
In 2006, it was discovered that nine of the satellite galaxies lie in a plane that intersects the core of the Andromeda Galaxy; they are not randomly arranged as would be expected from independent interactions. This may indicate a common tidal origin for the satellites.
==Collision with the Milky Way==
The Andromeda Galaxy is approaching the Milky Way at about 110 kilometres (68 miles) per second. It has been measured approaching relative to the Sun at around 300 km/s (190 mi/s) as the Sun orbits around the center of the galaxy at a speed of approximately 225 km/s (140 mi/s). This makes the Andromeda Galaxy one of about 100 observable blueshifted galaxies. Andromeda Galaxy's tangential or sideways velocity concerning the Milky Way is relatively much smaller than the approaching velocity and therefore it is expected to collide directly with the Milky Way in about 2.5-4 billion years. A likely outcome of the collision is that the galaxies will merge to form a giant elliptical galaxy or possibly large disc galaxy. Such events are frequent among the galaxies in galaxy groups. The fate of Earth and the Solar System in the event of a collision is currently unknown. Before the galaxies merge, there is a small chance that the Solar System could be ejected from the Milky Way or join the Andromeda Galaxy.
Category:Real objects
Category:Objects
Category:Galaxies