| 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 | 24 ± 0 km/s[1] |
| Distance | 2.25 ± 0.20 Mly (690 ± 60 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] | |
| See also: Galaxy, List of galaxies | |
Leo A ( also known as Leo III ) is an irregular galaxy that is part of the Local Group. It lies 2.25 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. The presence of RR Lyrae variables shows that the galaxy has an old stellar population that is up to 10 billion years in age.[6]
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 lower rate of stellar evolution than in the Milky Way galaxy. The Leo A galaxy shows sign of increased star formation some time within the last billion years, although the current level is low. There are four H II regions powered by short-lived, O-class stars.[7]