Andromeda's satellite galaxies
Encyclopedia
Andromeda Galaxy
The Andromeda Galaxy is a spiral galaxy approximately 2.5 million light-years from Earth in the constellation Andromeda. It is also known as Messier 31, M31, or NGC 224, and is often referred to as the Great Andromeda Nebula in older texts. Andromeda is the nearest spiral galaxy to the...
(M31) has satellite galaxies
Satellite galaxy
A satellite galaxy orbits a larger galaxy due to gravitational attraction. Although a galaxy is made of a large number of objects which are not connected to each other, it has a center of mass, which represents a weighted average of the positions of each component object...
just like the Milky Way Galaxy. Orbiting M31 are at least 14 dwarf galaxies
Dwarf galaxy
A dwarf galaxy is a small galaxy composed of up to several billion stars, a small number compared to our own Milky Way's 200-400 billion stars...
: the brightest and largest is M32, which can be seen with a backyard telescope. The second brightest and closest one to M32 is M110. The other galaxies are fainter, and were mostly discovered only starting from the 1970s.
On January 11, 2006, it was announced that Andromeda's faint companion galaxies lie on or close to a single plane running through Andromeda's center. This unexpected distribution is not obviously understood in the context of current models for galaxy formation. The plane of satellite galaxies points toward a nearby group of galaxies (M81 group), possibly tracing the large-scale distribution of dark matter
Dark matter
In astronomy and cosmology, dark matter is matter that neither emits nor scatters light or other electromagnetic radiation, and so cannot be directly detected via optical or radio astronomy...
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Table of known satellites
Andromeda's satellites are listed here by discovery (orbital distance is not known).| Name | Type | Distance from Sun Sun The Sun is the star at the center of the Solar System. It is almost perfectly spherical and consists of hot plasma interwoven with magnetic fields... (million ly Light-year A light-year, also light year or lightyear is a unit of length, equal to just under 10 trillion kilometres... ) |
Magnitude Apparent magnitude The apparent magnitude of a celestial body is a measure of its brightness as seen by an observer on Earth, adjusted to the value it would have in the absence of the atmosphere... |
Year discovered |
|---|---|---|---|---|
| M32 Messier 32 Messier 32 is a dwarf elliptical galaxy about 2.65 million light-years away in the constellation Andromeda. M32 is a satellite galaxy of the famous Andromeda Galaxy and was discovered by Le Gentil in 1749. M32 measures only 6.5 ± 0.2 kly in diameter at the widest point... |
dE2 | 2.48 | +9.2 | 1749 |
| M110 Messier 110 Messier 110 is a dwarf spheroidal galaxy that is a satellite of the Andromeda Galaxy. M110 contains some dust and hints of recent star formation, which is unusual for dwarf elliptical galaxies in general.-History:... |
dE6 | 2.69 | +9.4 | 1773 |
| NGC 185 NGC 185 NGC 185 is a dwarf spheroidal galaxy about 2.08 million light-years away in the constellation Cassiopeia. It is a member of the Local group, and is a satellite galaxy of the Andromeda Galaxy . NGC 185 was discovered by William Herschel on November 30, 1787, and he cataloged it "H II.707"... |
dE5 | 2.01 | +11 | 1787 |
| NGC 147 NGC 147 NGC 147 is a dwarf spheroidal galaxy about 2.58 Mly away in the constellation Cassiopeia. NGC 147 is a member of the Local group of galaxies and a satellite galaxy of the Andromeda Galaxy . It forms a physical pair with the nearby galaxy NGC 185,another remote satellite of M31. It was... |
dE5 | 2.2 | +12 | 1829 |
| Andromeda I Andromeda I Andromeda I is a dwarf spheroidal galaxy about 2.40 million light-years away in the constellation Andromeda. Andromeda I is part of the Local group of galaxies and a satellite galaxy of the Andromeda Galaxy . It is roughly 3.5 degrees south and slightly east of M31... |
dSph | 2.43 | +13.2 | 1970 |
| Andromeda II Andromeda II Andromeda II is a dwarf spheroidal galaxy about 2.22 Mly away in the constellation Andromeda. It is part of the Local group of galaxies and is a satellite galaxy of the Andromeda Galaxy but it's also situated closely to the Triangulum Galaxy , it is not quite clear if it is a satellite of the... |
dSph | 2.13 | +13 | 1970 |
| Andromeda III Andromeda III Andromeda III is a dwarf spheroidal galaxy about 2.44 million light-years away in the constellation Andromeda. And III is part of the Local group of galaxies and is a satellite galaxy of the Andromeda Galaxy . And III was discovered by Sidney van den Bergh on photographic plates taken in 1970 and... |
dSph | 2.44 | +10.3 | 1970 |
| Andromeda IV Andromeda IV Andromeda IV might be an irregular satellite of the Andromeda Galaxy; however it is more probably not a galaxy at all, but a loosely bound star cluster or some other background feature.... * |
dIm? | 1972 | ||
| Andromeda V Andromeda V Andromeda V is a dwarf spheroidal galaxy about 2.52 Mly away in the constellation Andromeda.-History:Andromeda V was discovered by Armandroff et al... |
dSph | 2.52 | +15.4 | 1998 |
| Pegasus Dwarf Pegasus Dwarf Spheroidal Galaxy The Pegasus Dwarf Spheroidal is a dwarf spheroidal galaxy about 2.7 million light-years away in the constellation Pegasus... (Andromeda VI) |
dSph Dwarf spheroidal galaxy Dwarf spheroidal galaxy is a term in astronomy applied to low luminosity galaxies that are companions to the Milky Way and to the similar systems that are companions to the Andromeda Galaxy M31... |
2.55 | +14.5 | 1998 |
| Cassiopeia Dwarf Cassiopeia Dwarf The Cassiopeia Dwarf is a dwarf spheroidal galaxy about 2.58 Mly away in the constellation Cassiopeia. The Cassiopeia Dwarf is part of the Local group of galaxies and a satellite galaxy of the Andromeda Galaxy .... (Andromeda VII) |
dSph | 2.49 | 1998 | |
| Andromeda VIII Andromeda VIII Andromeda VIII is a galaxy discovered in August 2003. It is a companion galaxy to the Andromeda Galaxy, M31, and evaded detection for so long due to its diffuse nature... |
dSph | 2.7 | +9.1 | 2003 |
| Andromeda IX Andromeda IX Andromeda IX is a dwarf spheroidal satellite of the Andromeda Galaxy, it was discovered in 2004 by resolved stellar photometry from the Sloan Digital Sky Survey , by Zucker et al.... |
dSph | 2.5 | +16.2 | 2004 |
| Andromeda X Andromeda X Andromeda X is a dwarf spheroidal galaxy about 2.9 million light-years away from the Sun in the constellation Andromeda. Discovered in 2005, And X is a satellite galaxy of the Andromeda Galaxy .- External links :* *... |
dSph | 2.9 | +16.2 | 2005 |
| Andromeda XI | 2006 | |||
| Andromeda XII | 2006 | |||
| Andromeda XIII | 2006 | |||
| Tidal Stream Northwest (Tidal Stream E and F) | 2009 | |||
| Tidal Stream Southwest | 2009 | |||
| Triangulum Galaxy Triangulum Galaxy The Triangulum Galaxy is a spiral galaxy approximately 3 million light years from Earth in the constellation Triangulum. It is catalogued as Messier 33 or NGC 598, and is sometimes informally referred to as the Pinwheel Galaxy, a nickname it shares with Messier 101... (M33) |
SA(s)cd | 2.59 | +6.27 | 1654? |
* It is uncertain whether is a companion galaxy of the Andromeda Galaxy
Andromeda Galaxy
The Andromeda Galaxy is a spiral galaxy approximately 2.5 million light-years from Earth in the constellation Andromeda. It is also known as Messier 31, M31, or NGC 224, and is often referred to as the Great Andromeda Nebula in older texts. Andromeda is the nearest spiral galaxy to the...
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Interacting with Andromeda
NASA
The National Aeronautics and Space Administration is the agency of the United States government that is responsible for the nation's civilian space program and for aeronautics and aerospace research...
's Spitzer Space Telescope
Spitzer Space Telescope
The Spitzer Space Telescope , formerly the Space Infrared Telescope Facility is an infrared space observatory launched in 2003...
shed light on the Andromeda Galaxy's violent past. The images show that one of Andromeda's satellite galaxies, M32, blasted through one of Andromeda's spiral arms a few million years ago. Infrared
Infrared
Infrared light is electromagnetic radiation with a wavelength longer than that of visible light, measured from the nominal edge of visible red light at 0.74 micrometres , and extending conventionally to 300 µm...
pictures of Andromeda's two spiral arms demonstrate that they and the prominent star
Star
A star is a massive, luminous sphere of plasma held together by gravity. At the end of its lifetime, a star can also contain a proportion of degenerate matter. The nearest star to Earth is the Sun, which is the source of most of the energy on Earth...
-forming ring are separate structures. The images also show a hole where the rings seem to split into arcs. This hole is where astronomers believe M32 punched through Andromeda's galactic disk.
External links
- Andromeda's thin sheet of satellites - Dark matter filiments or galaxtic cannibalism?
- Strange Setup: Andromeda's Satellite Galaxies All Lined Up