A small → dwarf irregular galaxy belonging to the
→ Local Group, which is
located in the constellation → Cassiopeia.
IC 10 is about 2.3 million light-years distant and about 5,000 light-years across.
With an absolute B magnitude of -16.5, IC 10 has an integrated luminosity that
is comparable to that of the → Small Magellanic Cloud,
although it is considerably smaller. Its → metallicity
is roughly a factor of 2 higher than
that of the SMC and in the same proportion smaller than → LMC’s.
Compared to other Local Group galaxies, IC 10 has a large population of newly
formed stars that are massive and intrinsically very bright, especially
→ Wolf-Rayet stars. Its W-R star density is larger than
those of the LMC and SMC. Moreover, the relative number of known → WC
to → WN type Wolf-Rayet stars is unusually high, which is
unexpected for IC 10’s metallicity. IC 10 is also known to be unusual in having
→ H I gas that extends about 7 times the optical dimensions of
the galaxy. IC 10 is the nearest example of a → starburst galaxy.
IC 10 was discovered by the American astronomer Lewis A. Swift (1820-1913) in
1887.
See also: Number 10 in the → Index Catalogue.
