All About Cancer Constellation
Cancer constellation is a medium-sized constellation in the Northern celestial hemisphere. About two thousands years ago, Cancer was the backdrop during the Northern Hemisphere’s summer solstice. This isn’t the case anymore as Taurus now takes this position when the summer solstice sun reaches its northernmost point for the year (precession of equinoxes), around June 21.
This position is also known as the Tropic of Cancer, where the Northern Hemisphere is tilted towards the Sun so it’s directly overhead at 23.437°N.
However, over the millenia, the constellation has stayed steadfast, so much so that on every June solstice, we still say that the sun is shining over the Tropic of Cancer, rather than the “tropic of Taurus.”
The coordinates of the Cancer constellation are 09h 00m 00s, +20° 00′ 00. It is bordered by Lynx to the north, Hydra to the south, Leo to the east and Gemini to the west. The constellation covers an area of 506 square degrees or 0.921% of the sky.
In Greek mythology, Cancer constellation represents the giant crab that Hera sent to kill Hercules. While he fought against the water serpent Hydra, Hercules killed the crab, sending it into the sky to rest among the stars.
Plato described Cancer as the “Gate of Men,” where people’s souls passed from heaven and took the human form as newborns. Ptolemy was the first to catalog the constellation among the 47 other constellations in Almagest.
In the 3rd century bc, the Greek poet Aratus, in his book Phenomena, mentioned Cancer, calling it “crab” which was later followed by Hipparchus and Ptolemy.
By Till Credner - Own work: AlltheSky.com
Major Stars in Cancer Constellation
Cancer constellation has clusters of stars. One of these clusters is called Praesepe (Messier 44) commonly known as the Beehive Cluster. It is an open cluster that contains 50 stars -- Epsilon Cancri being one of the brightest. In 1609, Galileo observed Beehive clusters with his telescope, locating 40 stars. On a dark night, the Beehive will appear as a faint cloud to naked eye.
Cancer constellation has another cluster that’s denser and smaller compared to Beehive Cluster and is almost the size of a full moon. It is called Messier 67 with 200 stars. It has an area of approximately 0.5 square degrees and is 2600 light-years from Earth.
The Cancer constellation has 121 stars, Beta Cancri (Tarf) being the brightest. Here are some of the major stars in the constellation.
Delta Cancri (Asellus Australis)
Delta Cancri is a moderately bright, double star in the Cancer constellation. It is located 180 light years from the Sun and can be visible from naked eye on a dark clear night. Its apparent magnitude (luminosity + distance from the Earth) is +3.94 and the absolute magnitude is +0.843.
Ptolemy’s Almagest records the occultation of Delta Cancri by Jupiter. This happened on September 3, B.C. 240.
Alpha Cancri (Acubens)
Alpha Cancri is one of the main stars in the Cancer constellation which also makes the constellation’s outline. The name Acubens was derived from Arabic word Al Zubanah, meaning “the claw.”
Alpha Cancri is the fourth largest star in the constellations and is 23 times brighter than the sun. It is also near the ecliptic and can be occulted by the Moon. Its apparent magnitude is 4.20 to 4.27 and its absolute magnitude is 0.46.
Lambda Cancri (Piautos)
Lambda Cancri is a main sequence class star and is located in the borders of the constellation. It is 78 times more luminous than the Sun. During a dark night, Piautos may be faintly visible to the eyes, showing blue-white hues.
Lambda Cancri is 2.1 times the mass of the Sun and is about 550 light-years distant from the Sun. In Chinese, Guàn (Beacon Fire) refers to the asterism consisting of Lambda Cancri and Psi-Phi 1 and 15 of kankri.
55 Cancri (Copernicus)
55 Cancri is part of the Cancer constellation and is located 40 light years away. It is a yellow dwarf star and has a mass similar to that of the Sun.
The 55 Cancri system is known to have four planets, the fifth one was added later. The system may also have more planets that are not known yet.
The coordinates are 08h 52m 35.8s, 28° 19′ 51. The apparent magnitude of 55 Cancri is 13.15 and absolute magnitude is +5.50.
Epsilon Cancri (Meleph)
Epsilon Cancri is a binary star in the Cancer constellation. Its solar mass is 2.75 times that of the Sun. It is also one of the brightest stars in the Beehive Cluster. The apparent visual magnitude of Epsilon Cancri is +6.29 which means that it can be hard to see it with a non aided eye.
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Cancer is represented by the crab and is the fourth astrological sign in the Zodiac. People born between June 21 - July 22 are associated with Cancer zodiac.
Cancer’s ruling planet is the Moon, which represents self-care and maternal comfort. Cancerians prefer to create cozy and safe spaces for themselves and may adopt caregiver roles.
Some of the famous Cancerians include: Meryl Streep, Princess Diana, Ariana Grande, Tom Hanks, and Robin Williams.