In wintertime Capella which is the brightest star in the constellation of Auriga the Charioteer is directly overhead. A striking constellation in the northern skies, Auriga lies above the horns of Taurus the Bull and forms the shape of a kite.
Auriga is named after
the son of Vulcan who invented the four-horse chariot. Another Greek legend
associates Auriga with Myrtilus who was Hermes’s son and the charioteer of
Oenomaus . The association of Auriga and Myrtilus is supported by depictions of
the constellation, which rarely show a chariot. Myrtilus's chariot was
destroyed in a race intended for suitors to win the heart of Oenomaus's
daughter Hippodamia. Myrtilus earned his position in the sky when Hippodamia's
successful suitor, Pelops, killed him, despite his complicity in helping Pelops
win her hand. After his death, Myrtilus's father Hermes placed him in the sky.
In Greco Babylonian times the constellation was called
Rukubi the Chariot. Arabic astronomers called the constellation Dhu al Inan the
Rein Holder. If we look even further into the story we see even different ideas
from ancient civilisations. Some Egyptians suggest that it represents Horus. In
Chinese mythology, Auriga's stars were incorporated into several
constellations, including the celestial emperors' chariots, made up of the
modern constellation's brightest stars.
The brightest star in Auriga is Capella which is the 6th brightest star in the sky. Capella whose name means the Goat Star, which is the same name given to the star by the Sumerian astronomers. However Arabic astronomers called it Al Rakib the driver because it lies so far north it was prominent in the evening sky before other stars became visible and so apparently is watching over them. It has a magnitude of 0.1 and it’s a G class giant star slightly cooler than our Sun and is 43 light years distant.
In 1899 astronomers discovered that Capella was not a single
star but a double star. But there's more going on with Capella as there is
another component to this system, a pair of small red stars, meaning that where
we see just one star there are actually 4!
In brightness it is virtually equal to Vega in the
constellation of Lyra the Lyre but it is of a very different colour, its
yellowish tinge contrast sharply with the steely blue of Vega. Both are
circumpolar from Britain, they can be seen all year round, although they both
will get very close to the horizon as seen from Britain. They lie on opposite
sides of the north pole star and at roughly the same distance from it. This
mean that when Capella is high up Vega is low down and vice versa. From Britain
Capella is overhead during winter evenings while in summer it is Vega that
occupies that position.
Slightly to the right and just below Capella is a little but
quite distinct triangle of stars called the Haedi or the kids. They are
referred to as the Kids because where the she goat goes the baby goats or kids will always follow!! The top star in the
triangle is epsilon, bottom left star is eta and the bottom right is zeta.
Epsilon was known to the Arab astronomers as Al Maaz the He
Goat. To Ulug Beg as Al Anz the meaning
of the name appears to be unknown. Epsilon is a F class supergiant white star its distance in not
known with any great certainty, but it could be about 2,000 light years away.
It normally it shines at around magnitude 3.0 but every 27 years it fades to
magnitude 3.8 where it remains for between 640–730 days – about two years.
Epsilon is eclipsed by an unseen and unknown very large companion star or cloud
of dust. The star’s last dimming was
from 2009 to 2011. The next should begin
around 2038!
Zeta was known to the Arabic astronomers as Al Said al Thani
or The Second Arm. Zeta is another eclipsing binary where the companion star
cannot be seen with the naked eye and varies between magnitude 3.7-4.1 over a
period of 972 days. Zeta is a K class
giant star lying 790 light years away.
The third component eta has no name. It lies 243 light years
away. It is a B3 class star making it much hotter than the Sun, eta has a
brightness of magnitude 3.2.
Beta or Menkalinan which means ‘Shoulder of the Charioteer’,
is the second brightest star in Auriga and is found to the left of Capella with
a magnitude of 2.0 the same brightness as the North Star. It is an A class star
with a surface temperature of around 8,8,00 degrees much hotter than our Sun.
It lies at a distance of 82 light years.
A line drawn down from beta will reach the star theta or
Mahasin with means the ‘Wrist of the Charioteer’. Theta has a magnitude of 2.6
and is an A class star 166 light years away.
From eta which is the top star of the Haedi or kids a line
drawn down and past zeta will come across iota or Al Kab which means the
‘Shoulder of the Rein holder’ this is the same name as beta, a charioteer can
be seen as the same as a reign holder. It is quite common for different names
of stars to have the same meaning. Iota lies at a distance of 490 light years
and has a magnitude of 2.7. It is a K class giant star making it cooler than our Sun.
In 1930 for some reason the star that was originally
classified as gamma Auriga whose name was also known as Al Kab which means the
wrist of the reign holder was transferred to the constellation of Taurus the
Bull and re labelled at beta Tauri. It makes no sense at all as it is the
bottom of the kite shape which used to form Auriga. Again, this is a situation
that in some star maps pre 1930 sometimes the star was sometimes placed in
Auriga and other times put into Taurus.
There are some interesting variable stars in Auriga one is
AE Auriga which normally shines at magnitude 6.0 which is the limit of naked
eye visibility under the very best of sky conditions. However, it does vary
irregularly. It is passing through the Flaming Star Nebula, this is a nebula
that reflects light from nearby stars. This nebula is about 9 light years wide
and it’s believed that AE Auriga has only recently entered the nebula.
There was a nova in Auriga in 1891 and is listed as T
Auriga. When it was discovered, It had a magnitude of 5.0 on January 23, 1892,
by Thomas David Anderson 1853-1932 who was a Scottish amateur astronomer It
became visible to the naked eye by December 10, 1891, as shown on photographic
plates examined after the nova's discovery. It then brightened from December 11
to December 20, when it reached a maximum magnitude of 4.4. T Auriga faded
slowly in January and February 1892, then faded quickly during March and April,
reaching a magnitude of 15 in late April, at which point it could only be seen
with a fairly large telescope.
There are 3 messier objects in Auriga, they are all open
clusters which are young groups of stars only a few million years old and
contain only a few dozen or few hundred stars
each.
M36 the Pinwheel
Cluster which is an open cluster around 4,100 light years away. You cannot see
it with the naked eye with a magnitude of 6.3 you would need a pair of
binoculars to see it.
M37 is another open cluster at magnitude 6.2 although it is
the brightest of the three open clusters in Auriga you would still need a pair
of binoculars to find it. It is 4,500
light years away.
M38 The Starfish Cluster is the faintest of the open
clusters here at magnitude 7.4. It is around 4,200 light years away.
www.theramblingastronomer.co.uk
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