Satellite galaxies of the Milky Way
The Milky Way has several smaller galaxies gravitationally bound to it, as part of the Milky Way subgroup. This subgroup is part of the local galaxy cluster, the Local Group.[1]
There are about 30 small galaxies confirmed to be within 420 kiloparsecs (1.4 million light-years) of the Milky Way, though not all of them are necessarily in orbit. Of those, the only ones visible to the naked eye are the Large and Small Magellanic Clouds, which have been observed since prehistory. Measurements with the Hubble Space Telescope in 2006 suggest the Magellanic Clouds may be moving too fast to be orbiting the Milky Way.[2] Of those galaxies confirmed to be in orbit, the largest is the Sagittarius Dwarf Elliptical Galaxy, which has a diameter of 20,000 light-years (6,100 pc) or roughly a fifth that of the Milky Way.
Contents
Characteristics
Satellite galaxies that orbit, from 1,000 ly (310 pc) of the edge of the disc of the Milky Way Galaxy, to the edge of the dark matter halo of the Milky Way at 980×103 ly (300 kpc) from the center of the Galaxy,[note 1] are generally depleted in hydrogen gas compared to those that orbit more distantly. This region is the dense hot gas halo of the Milky Way, which strips cold gas from the satellites. Satellites beyond this region still retain copious quantities of gas.[3][4]
List
The Milky Way's satellite galaxies include the following:[5]
| Name | Diameter (kpc) | Distance (kpc) |
Type | Discovered |
|---|---|---|---|---|
| Canis Major Dwarf | 1.5 | 8 | Irr | 2003 |
| Sagittarius Dwarf | 2 | 20 | E | 1994 |
| Large Magellanic Cloud | 4 | 48.5 | SBm | prehistoric |
| Small Magellanic Cloud | 2 | 61 | Irr | prehistoric |
| Ursa Major II Dwarf | 0.2 | 30 | dG D | 2006 |
| Ursa Minor Dwarf | 0.4 | 60 | dE4 | 1954 |
| Draco Dwarf | 0.7 | 80 | dE0 | 1954 |
| Sculptor Dwarf | 0.8 | 90 | dE3 | 1937 |
| Sextans Dwarf Spheroidal | 0.5 | 90 | dE3 | 1990 |
| Carina Dwarf Spheroidal | 0.5 | 100 | dE3 | 1977 |
| Ursa Major I Dwarf | - | 100 | dG D | 2005 |
| Fornax Dwarf | 0.6 | 140 | dE2 | 1938 |
| Leo II | 0.7 | 210 | dE0 | 1950 |
| Leo I | 0.5 | 250 | dE3 | 1950 |
| Leo IV | 0.3 | 160 | dSph | 2006 |
| Leo V | 0.08 | 180 | dSph | 2007 |
| Leo T | 0.34 | 420 | dSph/dIrr | 2006 |
| Boötes I | 0.3 | 60 | dSph | 2006 |
| Boötes II | 0.1 | 42 | dSph | 2007 |
| Boötes III | 1 | 46 | dSph? | 2009 |
| Coma Berenices | 0.14 | 42 | dSph | 2006 |
| Segue 2 | 0.07 | 35 | dSph | 2007 |
| Canes Venatici I | 2 | 220 | dSph | 2006 |
| Canes Venatici II | 0.3 | 155 | dSph | 2006 |
| Hercules | 0.7 | 135 | dSph | 2006 |
| Pisces II | 0.12 | 180 | dSph | 2010 |
| Reticulum II | - | 30 | dSph | 2015 [6][7] |
| Eridanus II | - | 380 | dSph | 2015 [6] [7] |
| Horologium | - | 100 | dSph? | 2015 [6] [7] [lower-alpha 1] |
| Pictoris | - | 115 | dSph? | 2015 [6] [7] [lower-alpha 1] |
| Phoenix II | - | 100 | dSph? | 2015 [6] [7] [lower-alpha 1] |
| Kim 2/Indus I | - | 100 | dSph? | 2015 [6] [7] [lower-alpha 1] |
| Grus | - | 120 | dSph | 2015 [6] |
| Eridanus III | - | 90 | dSph? | 2015 [6] [7] [lower-alpha 1] |
| Tucana II | - | 70 | dSph | 2015 [6] [7] |
Clickable map
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Streams
The Sagittarius Dwarf is in the process of being consumed by the Milky Way, and is expected to pass through it within the next 100 million years. The Sagittarius Stream is a stream of stars in polar orbit around the Milky Way leeched from the Sagittarius Dwarf. The Virgo Stellar Stream is a stream of stars that is believed to have once been an orbiting dwarf galaxy that has been completely distended by the Milky Way's gravity.
See also
Footnotes
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| Location |
Milky Way → Milky Way subgroup → Local Group → Virgo Supercluster → Laniakea Supercluster → Observable universe → Universe
Each arrow (→) may be read as "within" or "part of". |
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| Galactic core | |||||||||
| Spiral arms | |||||||||
| Satellite galaxies |
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| Related | |||||||||
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Earth → Solar System → Local Interstellar Cloud → Local Bubble → Gould Belt → Orion Arm → Milky Way → Milky Way subgroup → Local Group → Virgo Supercluster → Laniakea Supercluster → Observable universe → Universe
Each arrow (→) may be read as "within" or "part of". |
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This galaxy-related article is a stub. You can help Wikipedia by expanding it. |
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