Claudius Ptolemaist was the 2nd century Greek astrologer and he was the one who compiled a list of the 48 constellations. His work might have been used by Islamic and European medieval scholars for thousands of years. Cancer is one of these constellations and is represented by a crab. It is a medium sized constellation, 12th constellation of Zodiac and is located on the elliptical plane, bordered by lynx to the north, Gemini to West, Leo to east and Leo minor to northeast, Canis minor to southwest and Hydra to south. The cancer constellation is visible easily.
Name & meaning
In the mythology it was a piece of the 12 labors of Hercules. When Hercules was in the fight with multi headed beast whose name was Hydra, the Hera who was a Goddess dislike Hercules sent a crab to create distraction. With its claws crab grabbed Hercules, but soon after was crushed by the mighty foot of Hercules. Hera gave tribute to this sacrifice and gave him a place in the sky. The crab failed and because of this the gods did not give any of the bright stars.
History
The first example which was recorded exists in the second millennium BCE about cancer constellation where its knowledge was with Acadian who was also an astronomer as sun of the south. It was the name given because during the ancient relic its position was at the summer solstice. Gate of men was the name given to cancer by classical relics which was due to the belief that it is the gateway from where souls come and go from heaven. The relatives of the cancer were given faintness so it is also described as dark sign the entire history.
Its stature has remained steadfast as a zodiac constellation over millennia. It was thought that its position might have changed.
Notable features
Cancer constellation is comparatively faint still there are many noticeable stars. The first is beta chancre also called the glance or the eye. It is the brightest one and is 660 times much brighter than sun. It belongs to K class and is orange huge star which is 290 light years far from earth. The second star is more far and is about 65 times the distance of Pluto from sun which means its orbital period is 76,000 light years.
- Delta Cancri is another star from cancer constellation and is an orange giant star which is 180 light years away from the earth. It is the 2nd brightest star and is also popular as Beehive Cluster.
- Gamma Cancri is bit further and is 158 light years from the earth. Asellus Boealis is its Latin name meaning northern ass.
- Alpha Cancri is the4th brightest star and is also called Acubens. It is located 174 light years from the earth and is a multiple star system including alpha A and B.
Cancer is also dwelling for many deep sky objects like Beehive Cluster. The clutter around it is relative of our solar system and is having hue population of stars as compared to the nearby cluster. The beehive cluster dark side appears like nebulous to unaided eye and is known since ancient times.
Ptolemy called this mass heart of cancer and is among few objects which Galileo studies with his telescope. There are white dwarfs and well as red giants which truly represents the stellar evolution stages.
11 white dwarfs have been identified till now. These dwarfs tell the final phase of evolution of colossal stars, which belonged to spectral type B. The rare ones are the brown dwarfs because they are vanished by tidal stripping from halo. Then comes M67 which is visible due to the alpha Cancri west. This is not the oldest one, but there are few other stars in the Milky Way which are more older than M67. M67 is an imperative lab for knowing and studying evolution of stars, since all its stars are of similar age and is situated at the same distance.
M67 is having more than hundred stellar like to sun and red giants though the actual number studied is above five hundred.
Then comes NGC 2775 which is sixty million light years away from the earth. It is a particular blend of the spiral galaxy having a light bulge in the middle. The formation of the stellar is confined within the ring like wound arms and in the past thirty years the galaxy is the location of five supernovae explosions.
DX Cancri is at the magnitude of 14 and is a cool dwarf red star that is 9% less than the sun mass. It is called the flare star that shows changes in the brightness. This star cannot be seen with naked eye though it is the 18th closest to sun.
Now comes 55 Cancri which is also called Rho1 Cancri and is a binary star system that is located at the 41 light years away. It is also having its own solar system. There is yellow dwarf, small red dwarf and is separated by a thousand times distance from earth to sun.
In the year 2007 there were 5 extra solar planets were also discovered and confirmed that orbits 55 Cancri A. the inner planet is super earth which is terrestrial and its mass is like Neptune, while the outer most planets are known as Jovian planets with mass that is similar to the Jupiter.
Finding cancer constellation
Along the ecliptic 12 constellation cancer is very easy to find even with binoculars and telescopes. It is located in the 2nd quadrant of NQ2 and can be observed at the latitudes + 90 degree and -60 degree. It is having the 506-degree area which makes it 31st largest constellation.
With the cancer constellation there is just 1-meter shower associated. The peak date is 16th January approx for delta Cancrids. The shower is minor and is having average fall rate that is 4 per hour and the meteors are also very swift.