Corona Borealis The Northern Crown
Corona Borealis the
Northern Crown which was given as a wedding present by Bacchus to
Ariadne and was then cast by him into the sky when she died. It
consists of an arc of seven fairly faint stars with the exception of
alpha.
Alpha or alphecca
which means ‘the bright (star) of the broken (ring of stars)’ is
an AO class star at magnitude 2.2. it lies 75light years away.
Beta of Nusakan
which means ‘The two lines (of Stars)’ is 112 light years
distant. It is an A9 class star with a magnitude of 3.7
Gamma has a
magnitude of 3.8 and is a B9 class star, it is 146 light years away.
There are two
special variable stars in this small constellation.
R Coronae Borealis
is a yellow supergiant which usually is just at the limit of naked
eye visibility at magnitude 6.0 but at unpredictable times it will
fade to as faint as magnitude 14. It is thought that this is caused
by carbon rich particles building up in the atmosphere blocking the
light from the star reaching Earth. These particles then disappear
and the star then brightens once again.
There are only about
100 of these stars known. R itself was discovered by Edward Piggot in
1795.
T Coronae Borealis is also know as the Blaze Star, its a nova which
erupted in 1866 reaching magnitude 2.2 and going novae again in 1946
reaching magnitude 3.0. It is called the Blaze Star because until
around 20 years ago it was one of the few stars that had been
observed to go novae more than once. Astronomers know today that all
nova erupt more than once on times scales of decades or centuries.
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