MAJOR STARS IN CANCER Acubens – α Cancri (Alpha Cancri) Acubens, Alpha Cancri, is only the fourth brightest star in Cancer. Its apparent magnitude varies between 4.20 and 4.27. The star is sometimes also called Al Zubanah or Sertan. The name Al Zubanah comes from the Arabic az-zubānah, which means “claws,” while Sertan is derived from saraţān, which means “the crab.” Alpha Cancri is a multiple star system located approximately 174 light years from Earth. The brightest component, Alpha Cancri A, is a white A-type main sequence dwarf. The star has an eleventh magnitude companion, Alpha Cancri B. The brighter star in the system is suspected to be a very close binary itself, consisting of two stars separated by 0.1 arcseconds. Acubens belongs to the spectral class A5m and has a luminosity 23 times that of the Sun. The star lies close to the ecliptic and can be occulted by the Moon and, rarely, by planets. Al Tarf – β Cancri (Beta Cancri) Beta Cancri is the brightest star in the constellation, with an apparent visual magnitude of 3.5. It is a binary star that consists of an orange K-type giant and a fourteenth magnitude companion 29 arcseconds away. Beta Cancri is approximately 290 light years distant. The star’s traditional name, Al Tarf (or just Tarf), is believed to be derived either from the Arabic aṭ-ṭarf, which means “the eye,” or aṭ-ṭarfah, which means “the glance (of Leo).” Asellus Australis – δ Cancri (Delta Cancri) Delta Cancri is an orange giant with an apparent magnitude of 3.94. It is 180 light years distant. It is the second brightest star in Cancer. It marks the location of Praesepe (Messier 44), the famous open cluster, also known as the Beehive Cluster. The star is also notable for its less famous name, Arkushanangarushashutu, which is the longest of all the known star names. It means “the southeast star in the Crab” in ancient Babylonian. The star’s more commonly used name, Asellus Australis, means “southern donkey colt” in Latin. Delta Cancri also lies close to the ecliptic and can be occulted by the Moon and, however rarely, by planets. Asellus Borealis – γ Cancri (Gamma Cancri) Gamma Cancri is a white A-type subgiant approximately 158 light years distant. It has an apparent visual magnitude of 4.66. The star’s traditional name, Asellus Borealis, means “northern donkey colt.” Like Alpha and Delta Cancri, Gamma Cancri is also located near the ecliptic and can be occulted. Delta and Gamma Cancri, the northern and southern donkey, are usually associated with an old Greek myth. Erastosthenes wrote that, in the war between the gods and the Giants that came after the clash with the Titans, the gods Hephaestus, Dionysus and several others rode on donkeys into battle. The Giants, who had never heard a donkey bray, thought the donkeys were monsters and fled. Dionysus later placed the donkeys in the sky to commemorate the event. He put them next to a star cluster which the Greeks called the Manger (Phatne). The cluster is now known as Praesepe or, more popularly, the Beehive Cluster. (In Latin, praesepe can mean both “hive” and “manger.”) 55 Cancri 55 Cancri is a double star that consists of a yellow main sequence dwarf belonging to the spectral class G8V and a 13th magnitude red dwarf that can only be seen through a telescope. The system is approximately 41 light years distant. 55 Cancri is notable because, as of 2010, astronomers have confirmed five extrasolar planets orbiting the primary star in the system, 55 Cancri A. This is one of the four known planetary systems known to have at least five planets. (Others are our solar system, Gliese 581 in the constellation Libra and HD 10180 in Hydrus.) The planet nearest to the star is believed to be a terrestrial planet with a mass similar to Neptune, while the outermost planets are believed to be Jovian planets, with masses comparable to that of Jupiter. Tegmine – ζ Cancri (Zeta Cancri) Zeta Cancri is a multiple star system approximately 83.4 light years from Earth. It contains at least four stars. Its traditional name, Tegmine, means “the shell of the crab.” The system has an apparent magnitude of 4.67. Zeta Cancri is composed of two binary stars, Zeta-1 Cancri and Zeta-2 Cancri, separated by 5.06 arcseconds. The first pair, Zeta Cancri A and Zeta Cancri B, are both yellow-white F-type main sequence dwarfs. They are separated by 1 arcsecond in the sky. The second pair, Zeta Cancri C and Zeta Cancri D, are a yellow G-type star and a 10th magnitude red dwarf separated by only 0.3 arcseconds. They have an orbital period of 17 years. λ Cancri (Lambda Cancri) Lambda Cancri is a blue-white B-type main sequence dwarf, approximately 419 light years distant. It has an apparent magnitude of 5.92. ξ Cancri (Xi Cancri) Xi Cancri is a spectroscopic binary star approximately 381 light years distant. It is sometimes also known as Nahn. The Xi Cancri system consists of Xi Cancri A, a yellow G-type giant with a magnitude of 5.16, and Xi Cancri B, a companion star located only 0.1 arcseconds away. The stars have an orbital period of 4.66 years.
Posted on: Mon, 04 Aug 2014 17:22:20 +0000