| Quoted from SEDS:
Discovered by Johann Elert Bode in 1774.
Messier 82 (M82, NGC 3034) is a remarkable galaxy of peculiar type in
constellation Ursa Major. It is usually classified as irregular, though
probably a distorted disk galaxy, and famous for its heavy star-forming
activity, thus a prototype member of the class of star bursting
galaxies.
Forming
a most conspicuous physical pair with its neighbor,
M81 (THE showpiece
galaxies for many Northern hemispherers), this galaxy is the prototype
of an irregular of the second type, i.e. a "disk" irregular. Its core
seems to have suffered dramatically from a semi-recent close encounter
with M81, being in a heavy starburst and displaying conspicuous dark
lanes. This turbulent explosive gas flow is also a strong source of
radio noise, discovered by Henbury Brown in 1953. The radio source was
first called Ursa Major A (strongest radio source in UMa) and cataloged
as 3C 231 in the Third Cambridge Catalogue of Radio Sources.
In the infrared light, M82 is the brightest galaxy in the sky; it
exhibits a so-called infrared excess (it is much brighter at infrared
wavelengths than in the visible part of the spectrum). This behavior can
also be observed for the companion of
M51,
NGC 5195,
and the peculiar galaxy
NGC 5128
(Centaurus A). The visual appearance is that of a silvery sliver, as
John Mallas described it.
Recently, over 100 freshly-formed (young) globular clusters have been
discovered with the Hubble Space Telescope. Their formation is probably
another effect triggered by the encounter with M81. It was estimated
that the most recent tidal encounter occurred between about 50 and
several 100 million years ago: STScI's most recent number was 600
million years, when the 100-million-year-long period of heavier
interaction began.
As a member of the
M81 group,
M82 is 12 million light years distant.
M82 was discovered on December 31, 1774 by
Johann
Elert Bode together with M81; he described it as a "nebulous patch",
about 0.75 deg away from M81, which "is very pale and of elongated
shape," and cataloged it as No. 18 in his catalog.
Pierre
Méchain independently rediscovered both galaxies as nebulous patches
in August 1779 and reported them to
Charles
Messier, who added them to
his
catalog after his position measurement on February 9, 1781.
M82 belongs to those few Messier objects which have been assigned a
Herschel
number,
H IV.79,
based on an observation of September 30, 1802, while
William
Herschel usually carefully avoided to give his numbers to Messier
objects.
William
Parsons, the Third Earl of Rosse, was the first to remark on the
dark dust lanes and patches visible in the central part of M82.
Halton Arp has included M82 as No. 337 in his
Catalogue of
Peculiar Galaxies.
One false, one true, and two possible supernovae have been reported
in M82 so far (July 2009):
- Lebofsky, Rieke, and Kailey reported the discovery of a
supernova, 1986D, which should have occurred in M82, and is e.g.
listed in Kenneth Glyn Jones' book. However, this "SN" turned out to
be a false alarm. Instead, a slightly variable 2-micrometer source
had fooled the discoverers.
-
Supernova 2004am was discovered lately on images taken at Lick
Observatory on November 21, 2003, when it was at mag 17.0.
-
Possible Supernova 2008iz was detected on April 17, 2009 in
radio observations made on March 24, 2008 by Brunthaler et.al.
at the Very Large Array (VLA), and also found in later radio
observations (Brunthaler et.al.
2009). Not observed in the visible light, it is suspected to
have been a supernova of type II.
- A possible supernova reported in June 2009, also in the radio
light.
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