Holmberg IX is a
dwarf irregular galaxy and a
satellite galaxy
A satellite galaxy is a smaller companion galaxy that travels on bound orbits within the gravitational potential of a more massive and Luminosity, luminous host galaxy (also known as the primary galaxy). Satellite galaxies and their constituents ...
of
M81, located in the constellation of
Ursa Major
Ursa Major, also known as the Great Bear, is a constellation in the Northern Sky, whose associated mythology likely dates back into prehistory. Its Latin name means "greater (or larger) bear", referring to and contrasting it with nearby Ursa M ...
. It is a Magellanic type galaxy, similar to the
Small Magellanic Cloud
The Small Magellanic Cloud (SMC) is a dwarf galaxy near the Milky Way. Classified as a dwarf irregular galaxy, the SMC has a D25 isophotal diameter of about , and contains several hundred million stars. It has a total mass of approximately 7 bill ...
, neighbour galaxy to the Milky Way Galaxy.
The galaxy is
named after
Erik Holmberg who first described it, though it was originally discovered by
Sidney van den Bergh
Sidney Van den Bergh (born 20 May 1929) is a retired Dutch-Canadian astronomer.
Van den Bergh showed an interest in science from an early age, learning to read with books on astronomy. In addition to being interested in astronomy, he also like ...
in 1959.
Based on the observed age distribution of stars it contains, 20% of its stellar mass formed within the last 200
Myr
Million years ago, abbreviated as Mya, Myr (megayear) or Ma (megaannum), is a unit of time equal to (i.e. years), or approximately 31.6 teraseconds.
Usage
Myr is in common use in fields such as Earth science and cosmology. Myr is also used w ...
, making it the youngest nearby
galaxy
A galaxy is a Physical system, system of stars, stellar remnants, interstellar medium, interstellar gas, cosmic dust, dust, and dark matter bound together by gravity. The word is derived from the Ancient Greek, Greek ' (), literally 'milky', ...
.
It is also home to one of two
yellow supergiant
A yellow supergiant (YSG) is a star, generally of spectral type F or G, having a supergiant luminosity class (e.g. Ia or Ib). They are stars that have evolved away from the main sequence, expanding and becoming more luminous.
Yellow supergiants ...
eclipsing binary
A binary star or binary star system is a Star system, system of two stars that are gravity, gravitationally bound to and in orbit around each other. Binary stars in the night sky that are seen as a single object to the naked eye are often resolved ...
systems.
References
Further reading
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External links
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M81's satellite galaxy Holmberg IXGALEX Completes Four Star-Studded Years in SpaceDwarf Galaxy Holmberg IX*
{{Sky, 09, 57, 32.1, +, 69, 02, 46, 12000000
Interacting galaxies
Dwarf irregular galaxies
05336
28757
28757
Ursa Major
M81 Group