Cancer (Pronounciation:Can-sir, Abbrev:Cnc, Latin:Cancri) is a constellation, one of 88 constellations that the night sky is divided into. The sky is not divided up equally between the constellations. Cancer takes up 505.872 sq. degrees of the night sky which equates to 1.23% of the night sky. Cancer is the 31st largest in terms of size in the night sky.
The constellation name means The Crab . The constellation is one of the original constellations that was devised by the Ancient Greco-Egyptian astronomer Ptolemy who lived between 90 A.D. and 168 A.D.
There are 6 stars that make up the main constellation. The hipparcos satellite scanned and detailed 1186 stars. There are 48 stars that can be seen with the naked eye in the constellation on a very clear night sky.
Cancer is a member constellation of the Zodiac grouping, a group of 12 star signs that astrologers use to predict someones future based on their date of birth and which constellation appeared when the Sun set. The Zodiac year may be divided up equally between the twelve signs but when they appear in the night sky no longer conforms to the Zodiac calendar. Cancer is an equatorial constellation that can be seen by countries nearest the Equator.
There are 2 deep space objects that were identified by Charles Messier in this constellation. There are no non-Messier deep space objects in this constellation that are covered at present on this site.
The image at the top right of this page was generated using Night Vision, a free to use and download application by Brian Simspon.
You can't just go to one location and arrive at the constellation because the constellation is made up of stars at different locations and different distances. The nearest main star in the constellation is at a distance of 130.57 light years and the furthest main star is a distance of 331.13 light years. The average distance to the main stars is 235.61 light years.
The caveat of these stars are that they are catalogued on this site. If you know of a star that is nearer or further then do let me know in the comments and I'll add it to the site. The stars mentioned are from the Hipparcos catalogue or have been added because of their special status.
The furthest star that is located in the constellation is HIP 44539 and it is 163081.7 light years away from the Sun. The furthest figure is derived from either the 1997 or 2007 Hipparcos star catalogue parallax figure and it has been known to produce distances that are wrong.
The dimmest star that can be seen in Cancer with the naked eye is 5 Cancri. The dim star has an apparent magnitude of 5.99. The dimmest star that a person is able to see with their naked eye is 6.0 magnitude based on the table in the reference. Ref: University of Michigan.
Up until the mid-2010, the star was known as 55 Cancri but because of its significance, I.A.U. elected to rename it in a competition. It significance is that Copernicus has a large than usual number of exoplanets in orbit round it. It has five planets in orbit round the star so far known as at April 2018.
The constellation is best view from the beginning of the year when it is the eastern hemisphere before disappearing about July time in the north west.
The best time to see this is from February when it appears in the northern directly. At the same time that the constellation is appearing, the Delta Cancrids meteors shower is happening. It is not visible for long as it disappearings in May.
Cancer was a crab in Ancient Greek mythology that Hera sent to make things harder for Hercules . It had little effect on the warrior as Hercules fought Hydra for the second labour. Hercules was the Illegitimate son of Zeus and a mortal. Hera, wife of Zeus was determined to exact revenge for her husband being unfaithful.
The only connection between Cancer the constellation and Cancer the disease is that they share the same name. You're not at a higher risk of getting the disease if you are born under the constellation of Cancer. Getting Cancer is down to other factors including but not limited to genes, lifestyle including smoking, eating and drinking.
If you are worried, talk to a doctor as I'm no medical professional. The reason why the disease is so called is because in the Ancient Greece, it was noted by Hippocrates and Galen amongst others that the veins round a tumour look like crabs. StackExchange
There are 17 Meteor Showers that occur during the year within this constellation based on information gathered from Adam Mickiewicz University (Poland). The list below are major ones and which I have a date period for.
|Name||Activity||Peak Activity||Closest Star|
|Northern delta Cancrids||16th January|
|Southern delta Cancrids||16th January|
|Beta Cancrids||5th February|
|Tau Cancrids||Oct 9-25||Oct 17||Tau Cancri|
The following list contains the stars that make up the constellation. For a larger list of stars in the entire constellation area, please visit the For a list of named stars, that is stars that don't start HD or HIP, please visit Cancer Star List page.
|Name||Bayer||Distance (Lt.Yr.)||Right Ascension||Declination||Spectral Type||Colour|
|Acubens||Alpha Cancri||188.32||08h 58m 29.20||+11d 51` 28.0||A5m||White|
|Altarf||Beta Cancri||303.41||08h 16m 30.95||+09d 11` 08.4||K4III||Orange|
|Asellus Borealis||Gamma Cancri||181.20||08h 43m 17.21||+21d 28` 06.9||A1IV||White|
|Asellus Australis||Delta Cancri||130.57||08h 44m 41.11||+18d 09` 17.5||K0III||Orange|
|Decapoda||Iota Cancri A||331.13||08h 46m 41.83||+28d 45` 36.0||G8Iab:||Yellow|
|Iota Cancri B||Iota Cancri B||279.01||08h 46m 40.00||+28d 45` 54.6||G8II...||Yellow|
|Is a Zodiac Sign||Yes|
|Area||505.872 sq. deg.|
|Percentage of Night Sky||1.23%|
|Site Exoplanet Count||30|
|Meteor Shower Count||17|
|Nearest Star||CU Cancri|
|Nearest Star with Exoplanet(s)||Copernicus|
|Dimmest Star||5 Cancri|
|Furthest Star||HIP 44539|
|Bright Star Count||48|
|Hipparcos Star Count||1186|
|Main Star Count||6|
|Messier Deep Space Object Count||2|
|Bordering / Neighbouring / Surrounding Constellations||Lynx|
*Note: The number of Non-Messier Deep Space Object Count relates to how many are covered on this site not how many there are.
|Messier 67 - King Cobra Cluster||Open Star Cluster||2.61-2.93 kly||+11:49||08h 50m 4|
|NGC 2535||Unbarred Spiral Galaxy||25:12:25||8h 11h 13m 5|
|NGC 2536||Barred Spiral Galaxy||25:10:46||8h 11h 15m 9|
|NGC 2623||Galaxy||250 MLy||+25d 45' 16.70||08h 38m 24m 093|
|Praesepe, the Beehive Cluster (M44, NGC2632)||Open Star Cluster||5770||+19:59||08h 40m 1|
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