Cancer is a zodiacal constellation in fact it is the faintest of the constellations that can be found in the zodiac. It can be found in the sky between Gemini the Twins and Leo the Lion both more spectacular examples of constellations in the zodiac.
The zodiac is an area of sky where all the planets in the
solar system can be found. The name zodiac dates to around 300 BCE and was
given by Greek and Roman astronomers, it means the little ring of animals.
Libra is not an animal and was added later around 50 BCE when part of the
constellation was hived off to form the constellation of Libra the Scales. The
zodiac was known by the Babylonian astronomers of around 4,000 years ago which
referred to this area of the sky at the Mirzata which means The Watch.
The constellation can best be described as looking like a
ghostly version of Orion the Hunter. In mythology Cancer represents a crab that
Juno queen of the gods sent to battle Hercules who was fighting the mufti headed
monster. The crab did not affect the outcome because Hercules killed the
monster and simply trod on the crab. However, as a reward for the efforts of
the crab it was placed in the sky for ever by the gods.
The Akkadians who had an empire which existed from about 2240 BCE to 2284 BCE described Cancer as the Sun of the South, perhaps due to the position of the constellation during the winter solstice many thousands of years ago.
The Persians called the constellation Kalakang, the
Chaldeans called it Sartono and the Arabs called it Al Saratan, all these names
refer to Cancer. In Babylon it was a turtle and around the 1000 CE the Saxons
called Cancer Crabba.
As I mentioned it is a very faint constellation the
brightest star is beta with a magnitude of only 3.5 it lies 390 light years
away and is a class K class giant star
cooler than our Sun. Bea is called Al Tarf which means the end of the southern
foot.
Alpha is called Acubens which means the claw it’s a magnitude 4.3 A class star and it is hotter
than our Sun. It lies at a distance of 178 light years.
Iota is a binary star the fainter star cannot be seen
without the use of a telescope. The main star has a magnitude of 4.0 and is a G
class giant star and is 320 light years away.
The last two stars I want to mention are not very bright,
but they play a part in a very interesting story. The stars are gamma with a
magnitude of 4.7 and delta with a magnitude of 3.9. Gamma is known as Asellus
Borealis of the Northern Donkey and delta is called Asellus Australis the
Southern Donkey they are either side of the open cluster M44 or Praesepe the
Beehive Cluster.
The letter M signifies that it is on the list of messier
objects catalogue by the French astronomer Charles Messier during the 18th
century on his quest to discover comets.
The term the Beehive appears to have been first used by
Admiral William Smythe during the 1840s when he described it as looking like a
swarm of bees. The cluster is a naked eye object it observed by Hipparchus
around 2,200 years ago who described it as a Little Cloud. It was one of the
first objects that Galileo looked at through his new telescope he counted
around 40 stars. Today we know there are over 1,000 stars there. The cluster
lies at a distance of 590 light years.
However, there is another older name for the beehive and
that is the Manger, which is a vessel that animals would have eaten out of.
According to some classical Greek myths and legend Greek heroes charged into
battle riding donkeys because the Titans were scared of the braying noise that
the donkeys made. For this good service two donkeys Asellus Australis and
Asellus Borealis were placed into the sky next to the manger to enjoy some
food.
The story becomes even more interesting because it appears
that around about 2,000 years ago the term the Crib starts to get used to
describe the star cluster. Is this some kind of biblical reference celebrating
the birth of Jesus?
There is a second messier object M67 which is a smaller open
cluster lying 2,600 light years and containing around 200 stars. At magnitude 6.1 a pair of binoculars will be
needed to see it. It is often the case when there is a particularly famous
messier object in a constellation another one can become overlooked, and this
is what happens to M67.
One lats piece of information regarding Cancer and I can never resist mentioning it is that Asellus Australis also has a Babylonian name which I believe holds a record for the longest name of a star, Arkushanangarushashutu, (22 letters) Try saying that quickly. The name translates to ‘the south-east star in the Crab’.
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