Leo A
| Leo A | |
|---|---|
 Leo A by Hubble Space Telescope
|
|
| Observation data (J2000 epoch) | |
| Constellation | Leo |
| Right ascension | 09h 59m 26.4s[1] |
| Declination | +30° 44′ 47″[1] |
| Redshift | 0.000067[1] |
| Distance | 2.6 ± 0.1 Mly (790 ± 40 kpc)[2][3] |
| Type | IBm[1] |
| Apparent dimensions (V) | 5′.1 × 3′.1[1] |
| Apparent magnitude (V) | 12.9[1] |
| Other designations | |
| Leo III, UGC 5364, DDO 69, PGC 28868[1] | |
Leo A ( also known as Leo III ) is an irregular galaxy that is part of the Local Group. It lies 2.6 million light-years from Earth. This galaxy was discovered by Fritz Zwicky in 1942.[4] The estimated mass of this galaxy is (8.0 ± 2.7) × 107 solar masses, with at least 80% consisting of an unknown dark matter.[5] It is one of the most isolated galaxies in the local group and shows no indications of an interaction or merger for several billion years. However, Leo A is nearly unique among irregular galaxies in that more than 90% of its stars formed more recently than 8 billion years ago, suggesting a rather unusual evolutionary history.[6] The presence of RR Lyrae variables shows that the galaxy has an old stellar population that is up to 10 billion years in age.[7]
The neutral hydrogen in this galaxy occupies in a volume similar to its optical extent, and is distributed in a squashed, uneven ring. The galaxy is not rotating and the hydrogen is moving about in random clumps. The proportion of elements with higher atomic numbers than helium is only about 1-2% of the ratio in the Sun. This indicates a much less complete conversion of gas into stars than in the Milky Way galaxy. The Leo A galaxy shows sign of increased star formation some time within the last 1-4 billion years, although the current level is low. There are four H II regions powered by short-lived, O-class stars.[8]
References
- ↑ 1.0 1.1 1.2 1.3 1.4 1.5 1.6 Lua error in package.lua at line 80: module 'strict' not found.
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External links
- Leo A on WikiSky: DSS2, SDSS, GALEX, IRAS, Hydrogen α, X-Ray, Astrophoto, Sky Map, Articles and images
