Cancer (constellation)

The constellation Cancer, the crab, is known in astronomy and astrology as one of the twelve constellations of the zodiac. Cancer is small and dim, and does not resemble a crab. It lies between Gemini to the west and Leo to the east, Lynx to the north and Canis Minor and Hydra to the south.

Notable features

The brightest star in Cancer is β Cancri, called Al Tarf ("the end" of the crab's leg). Other stars include Acubens (α), and the Aselli (the Asses), Asellus Borealis (γ) and Australis (δ), supposed to represent the asses that Dionysus and Silenus rode into battle.

55 Cancri[?] has a planetary system with two confirmed planets, one 0.84 times the mass of Jupiter and one possibly 5 times that mass.

Notable deep sky objects

Cancer is best noted among stargazers as the home of Praesepe[?] (M44), an open cluster also called the Beehive Cluster or the Gate of Men, which contains the star η Cancri.

M67, near Acubens (α Cnc), is one of the oldest clusters in the sky, more than 10 billion years old. It is a large, faint open cluster of about 100 stars.

Mythology

In Greek mythology, Cancer was a brave little crab who tried to stop Heracles from defeating the Hydra and was squashed for his efforts.

Astrology

The astrological sign Cancer (June 21 - July 22) is associated with the constellation. In some cosmologies, Cancer is associated with the classical element Water, and thus called a Water Sign (with Scorpio and Pisces). Its polar opposite is Capricorn.

In the 1970s there was a proposal to rename the zodiac sign, as some astrologers felt that an imagined association with the disease Cancer was off-putting.