NGC 404
A dwarf lenticular galaxy nicknamed Mirach's Ghost.
NGC 404, nicknamed "Mirach's Ghost," is a field galaxy in the constellation Andromeda, roughly 10 million light-years away. It sits just outside the Local Group and is not gravitationally tied to it. William Herschel spotted it in 1784, and it can be seen with small telescopes. Its proximity—within 7 arc-minutes—to the bright star Mirach makes it tricky to observe or photograph.
This galaxy is a very isolated dwarf lenticular type, slightly more luminous but smaller than the Small Magellanic Cloud. Unlike many early-type galaxies, it is rich in neutral hydrogen, most of which lies in two large rings around it. Low-level star formation occurs both at its center and in its outer regions. The outer gas disk and this star formation were likely triggered by one or more mergers with smaller galaxies about a billion years ago, possibly transforming NGC 404 from a spiral into a lenticular galaxy.
NGC 404 contains a low-ionization nuclear emission-line region (LINER), where spectral lines come from weakly ionized atoms. It also hosts a nuclear star cluster and likely a supermassive black hole with a mass of tens of thousands of solar masses.
Two methods have measured its distance. In 2003, infrared surface brightness fluctuations gave 9.9 ± 0.5 million light-years. The tip of the red giant branch method, using individual red supergiant stars, yielded 10.0 ± 1.2 million light-years. Averaged, these give a distance of 10.0 ± 0.7 million light-years.
A possible satellite, Donatiello I, was identified in 2018. This dwarf spheroidal galaxy shows little recent star formation, but its exact distance remains uncertain, so its status as a satellite is unconfirmed.
Quick Facts
- Epoch
- J2000
- Ra
- 01 · 09 · 27.0
- Dec
- +35 · 43 · 04
- Dist Ly
- 10.0 ± 0.7 Mly (3.07 ± 0.21 Mpc)A · a · none
- Z
- −48 ± 9 km/s
- Appmag V
- 11.2
- Constellation Name
- Andromeda
- Names
- UGC 718, PGC 4126
Facts from the source article.
Lore & Background
NGC 404 is a very isolated dwarf lenticular galaxy, a bit more luminous and smaller than the Small Magellanic Cloud. Unlike many other early-type galaxies, it is very rich in neutral hydrogen, most of it concentrated in a pair of large rings around it. It also has star formation both in its center and in 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 that 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 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.
Distance measurements have been made using two techniques. The infrared surface brightness fluctuations method gave a distance of 9.9 ± 0.5 million light years in 2003. The tip of the red giant branch method gave 10.0 ± 1.2 million light years. Averaged together, these give a distance estimate of 10.0 ± 0.7 million light years. In 2018, a possible satellite designated Donatiello I was identified, a dwarf spheroidal galaxy with little recent star formation, though difficulty in establishing its exact distance leaves its status as a satellite unconfirmed.
Reader's Guide
NGC 404 is significant as a nearby field galaxy that lies just beyond the Local Group, offering a laboratory for studying isolated galaxy evolution. Its nickname 'Mirach's Ghost' reflects the observational challenge posed by its proximity to the bright star Mirach, which makes it a difficult target for both visual observers and astrophotographers. The galaxy's richness in neutral hydrogen, arranged in large rings, and its low-level star formation in both the center and outer regions suggest a recent merger history that transformed it from a spiral into a lenticular galaxy about 1 billion years ago. The presence of a LINER nucleus, a nuclear star cluster, and a likely supermassive black hole of several tens of thousands solar masses adds to its astrophysical interest. The possible satellite Donatiello I, if confirmed, would further contextualize NGC 404's environment. Its distance, measured by two independent methods, places it at about 10 million light years, making it one of the closer galaxies beyond the Local Group.
Did You Know?
- NGC 404 is nicknamed 'Mirach's Ghost' because it lies within 7 arc-minutes of the bright star Mirach.
- It is a dwarf lenticular galaxy that is slightly more luminous but smaller than the Small Magellanic Cloud.
- A possible satellite galaxy, Donatiello I, was identified in 2018 but its status remains unconfirmed.
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