Cancer is a space constellation that is located in the northern sky. Its name means “the crab” in Latin due to its formation of the crab symbol in the sky. It is the 31st largest constellation in the sky and occupies an approximated area of 506 square degrees. The constellation is situated in the second quadrant of the northern hemisphere and is visible at latitudes between -60° and +90°. Its neighboring constellations are Gemini, Canis Minor, Leo, Hydra, Leo Minor, and Lynx. It is further noted that it belongs to the Zodiac family of constellations together with constellations such as Aries, Gemini, Leo, Virgo, Taurus, Libra, Sagittarius, Scorpius, Aquarius, Capricornus and Pisces. It is comprised of two Messier objects which are M67 (NGC 2682) and Beehive Cluster (M44, NGC 2632) and is home to two stars with established planets with the constellation’s brightest stars being Beta Cancri. However, it is the faintest of the thirteen constellations of the zodiac.
The constellation is visible in the sky in early spring and in late winter. It is then lost in the sun’s glare of July and august and resurfaces the morning sky of September. However, it is always safe to keep in mind that Cancer is faint and hence it’s neighboring constellations such as Leo star Regulus and Gemini stars Castor. It is also noted that the constellation is best viewed on a dark country sky since the chances of seeing it are high. The constellation makes up for its lackluster stars by comprising within it one of the sky’s brighter star clusters known as the Beehive cluster. In a dark sky and with unaided vision, the Beehive cluster appear as a tiny faint cloud. However, when seen through a binoculars, it turns into a sparkling city of stars (Zimmermann, 2017). This cluster is also known to have more stars than its neighbors and also appears to have similarities with the V-shaped Hyades star cluster hence the speculations that the two clusters could have been born from the same cloud of materials during the big bang.
Facts about the cancer constellation
This constellation is the faintest of the 12 zodiac constellations and is home to the beehive cluster and the praesepe cluster, the spiral galaxies which interact and the open cluster which are among some of the most famous deep space objects in astronomy. It can be found in the northern hemisphere second quadrant and can be viewed at +90 and -60 in the latitude map. Further, this constellation occupies 506 degrees squared making it the 31st largest constellation in the visible sky (Zimmermann, 2017).
It is bordered by Canis Minor, Gemini, Leo Minor and Lynx. The constellation is known to have two bright stars which have known planets; Al Tarf and Beta Cancrids and has a meteor shower known as the Delta cancrids. The constellation also has several statistics which include;
Alpha Cancri –The 4th brightest start in the constellation and is located 174 light years away from earth. Its luminosity is 23 times that of the sun and can be occulted by the moon by rarely by any planets.
Al-Tarf-Is the brightest star in the constellation with a magnitude of 3.5 and is approximately 290 light years ways from the earth. It is an orange K-type and is binary in nature.
Asellus Australis-is the second brightest star in the constellation and marks the location of the praesepe cluster. It is 180 light years away from the earth and lies very closely to the ecliptic.
Asellus Borealis – γ Cancri (Gamma Cancri)-Is approximately 158 light years away and is a type A white giant star.
55 Cancri-is located 83.4 light years away from the earth and is composed of multiple stars. The system is composed of 2 binary stars Zeta-1 and Zeta-2 separated by 5.06 Orbital arcs. The two binary stars have an orbital time period of 17 years.
ξ Cancri (Xi Cancri)- is a binary system located 381 light years away from the earth and its binary stars have an orbital time of 4.66 years
Significance of Cancer
Cancer’s holds the significant stature as a constellation of the zodiac with the significance remaining steadfast over the millennia. Over 2,000 years ago, the sun used to shine in front of the constellation but this is no longer the case in current times since it shines in front of constellation Taurus. Nonetheless, Cancer symbolizes the height of the summer sun (Zimmermann, 2017). As such, we usually say that the sun shines over the tropic of cancer on the June solstice and not the tropic of Taurus. The observance of this constellation has also been used by astronomers in better understanding the space. In this case, since the constellation has significant similarities with other constellations which are situated in other galaxies, its studying can help in correctly understanding the workings of other constellations and star clusters. In addition to its astronomical significance, the cancer constellation has been used in navigations since time immemorial hence it has been of significant importance to humanity.
Kim Ann Zimmermann (2017). Cancer Constellation: Facts About the Crab. Retrieved November 3, 2017 from https://www.space.com/16970-cancer-constellation.html