M31, The Andromeda Galaxy
| M31, Andromeda Galaxy, Borg 77ED with modified Canon XSi (28 x 4 min), click on image for full size |
The Andromeda Galaxy (Messier 31) is a spiral galaxy approximately 2,500,000 light-years away. It
is the nearest spiral galaxy to our own, the Milky Way. Andromeda is the largest galaxy of the Local
Group, which consists of the Andromeda Galaxy, the Milky Way Galaxy, the Triangulum Galaxy
(M33), and about 30 other smaller galaxies. The local group occupies a roughly dumbbell shaped
space about 10 million light years in diameter. Observations (2006) by the Spitzer Space Telescope
revealed that M31 contains one trillion stars, greatly exceeding the number of stars in our own
galaxy. However, a 2009 study concluded that Andromeda and the Milky Way are about equal in
mass. Recent estimates put the size of the stellar disk as being more than 220,000 light-years in
diameter.
Like the Milky Way, Andromeda Galaxy has satellite galaxies, consisting of 14 known dwarf galaxies.
The best known and most readily observed satellite galaxies are M32 (elliptical, lower right) and
M110 (spiral, upper left) which are both shown in this image. Based on current evidence, it appears
that M32 underwent a close encounter with M31 in the past. M32 may once have been a larger
galaxy that had its stellar disk removed by M31.
The Andromeda Galaxy is approaching our Sun at about 300 kilometres per second (190 mi/s), so it
is one of the few blue shifted galaxies. Most galaxies have their spectrum red shifted which shows
they are moving away from the Earth. The collision between M31 and the Milky Way is predicted to
occur in about 2.5 billion years. The two galaxies will likely merge to form a giant elliptical galaxy.
Such events are frequent among the galaxies in galaxy groups. The fate of the Earth and the Solar
System in the event of a collision are presently unknown, but there is a small chance that the Solar
System could be ejected from the Milky Way or even join Andromeda.
is the nearest spiral galaxy to our own, the Milky Way. Andromeda is the largest galaxy of the Local
Group, which consists of the Andromeda Galaxy, the Milky Way Galaxy, the Triangulum Galaxy
(M33), and about 30 other smaller galaxies. The local group occupies a roughly dumbbell shaped
space about 10 million light years in diameter. Observations (2006) by the Spitzer Space Telescope
revealed that M31 contains one trillion stars, greatly exceeding the number of stars in our own
galaxy. However, a 2009 study concluded that Andromeda and the Milky Way are about equal in
mass. Recent estimates put the size of the stellar disk as being more than 220,000 light-years in
diameter.
Like the Milky Way, Andromeda Galaxy has satellite galaxies, consisting of 14 known dwarf galaxies.
The best known and most readily observed satellite galaxies are M32 (elliptical, lower right) and
M110 (spiral, upper left) which are both shown in this image. Based on current evidence, it appears
that M32 underwent a close encounter with M31 in the past. M32 may once have been a larger
galaxy that had its stellar disk removed by M31.
The Andromeda Galaxy is approaching our Sun at about 300 kilometres per second (190 mi/s), so it
is one of the few blue shifted galaxies. Most galaxies have their spectrum red shifted which shows
they are moving away from the Earth. The collision between M31 and the Milky Way is predicted to
occur in about 2.5 billion years. The two galaxies will likely merge to form a giant elliptical galaxy.
Such events are frequent among the galaxies in galaxy groups. The fate of the Earth and the Solar
System in the event of a collision are presently unknown, but there is a small chance that the Solar
System could be ejected from the Milky Way or even join Andromeda.
