Mirach's Ghost
| NGC 404 | |
|---|---|
NGC 404 by Hubble Space Telescope; 1.68′ view
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| Observation data (J2000 epoch) | |
| Constellation | Andromeda |
| Right ascension | 01h 09m 27.0s |
| Declination | +35° 43′ 04″ |
| Redshift | -48 ± 9 km/s |
| Distance | 10.0 ± 0.7 Mly (3.07 ± 0.21 Mpc) |
| Apparent magnitude (V) | 11.2 |
| Characteristics | |
| Type | SA(s)0− |
| Apparent size (V) | 3′.5 × 3′.5 |
| Other designations | |
| UGC 718, PGC 4126 | |
NGC 404 is a field galaxy located about 10 million light years away in the constellation Andromeda. It was discovered by William Herschel in 1784, and is visible through small telescopes. NGC 404 lies just beyond the Local Group and does not appear gravitationally bound to it. It is notable for being within 7 arc-minutes of second magnitude star Mirach, making it a difficult target to observe or photograph and granting it the nickname "Mirach's Ghost".
NGC 404 is a very isolated dwarf lenticular galaxy, a bit more luminous and smaller than the Small Magellanic Cloud and unlike many other early-type galaxies is very rich in neutral hydrogen, most of it concentrated on a pair of large rings around it. It also has star formation both on its center and on its outermost regions, albeit at a low level
Both the outer gas disk and its star formation are assumed to have been triggered by one or several mergers with smaller galaxies roughly 1 billion years ago and it has been proposed NGC 404 is a former spiral galaxy that was transformed into a lenticular one by that event
NGC 404 contains a low-ionization nuclear emission-line region (LINER), a type of region that is characterized by spectral line emission from weakly ionized atoms. A nuclear star cluster is also present as well as -likely- a supermassive black hole, with a mass of several tens of thousands solar masses
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