Our pick of some of the best deep-sky objects to see in the constellation Cancer. In 2014 the International Astronomical Union (IAU) asked the public to help name certain exoplanets and their parent stars.Īs a result, 55 Cancri A is also known as Copernicus and the five known planets, in order of distance from Copernicus, are Janssen (e), Galileo (b), Brahe (c), Harriot (f) and Lipperhey (d).Ī message beamed to the system on 6 July 2003 is set to arrive in May 2044. Most excitingly, the star has a planetary system consisting of five or possibly more planets, several within its habitable zone.Īny moons existing around them, if sizeable enough, could play host to simple microbial life. 55 Cancri e has a mass 7.8 times and a radius just over twice that of our own planet, making it a 'super Earth'. An artist's concept showing how exoplanet 55 Cancri e compares with Earth. Its luminosity is around 59%, with a temperature of 5,165K compared to 5,778K for the Sun.ĥ5 Cancri A’s age is difficult to determine, with estimates ranging between 7.4–12.7 billion years – far older than the Sun’s 4.6 billion years. Physically, there are further similarities as 55 Cancri A has a diameter and mass equal to 96% of the Sun. The spectral type of 55 Cancri A is G8V, slightly cooler and redder than the G2V classification of our own Sun. Exoplanet 55 Cancri e is so close to its host star that its year lasts only 18 Earth days. 6.3 53 Cancri.ĥ5 Cancri is a true binary, consisting of a G-type star, 55 Cancri A, with a 13th magnitude red dwarf companion, 55 Cancri B. This pairing is false as ρ 1, at 40.3 lightyears, is just a fraction of the 894 lightyear distance of its ‘pair’, the mag. Using binoculars, our target star is the northernmost of a close pair of stars located two-thirds of the way from Iota towards ρ 2. 5.2 ρ 2 Cancri, more likely to be seen with the naked eye than ρ 1. The location of star 55 cancri in Cancer. 4.0 Iota (ι) Cancri, marking the northern end of the inverted Y-shape of Cancer. The best way to locate it is to first look for mag. 5.9 star on the threshold of naked-eye visibility from a typical dark sky site. 55 Cancriĥ5 Cancri (ρ 1 Cancri) is a mag. Discovered in 2014, this body is estimated to be nearly eight times the mass of Jupiter, orbiting the star once every 605 days at an average distance of 1.7 AU. The orbital period is estimated to be 76,000 years, but no evidence for any mutual orbital motion has been confirmed yet.Īltarf is also believed to have a planet. To lie around 2,600 AU from Altarf that’s around 65 times the Sun-Pluto distance. Shining at 14th magnitude, it is estimated 3.5.ĭespite its diminutive status, it should be borne in mind that Altarf is still 61 times larger and 870 times more luminous than the Sun.Ī faint red-dwarf companion accompanies the main star. Located at a distance of 290 lightyears, Altarf shines at mag. Its effective temperature is 3,717˚C, which is much cooler than our Sun at 5,505˚C. Credit: Pete LawrenceĪltarf has a spectral type of K4III Ba1, a cool orange K4 class giant with abundances of barium (chemical symbol Ba). The name is from the Arabic ‘ Al Tarf’ meaning ‘the End’, and it represents one of the Crab’s legs. The brightest star in Cancer isn’t Acubens as you might think, but Altarf (Beta (β) Cancri) which marks the southwest point of the constellation’s inverted Y-shaped pattern. What to observe in the constellation Cancer Altarf Equipment: SW 150P Newtonian, EQ5 GoTo Mount, QHY8L cooled ccd. M44 - The Beehive Cluster by Bill McSorley, Leeds, UK. Read on for our guide to some of the best things to see in Cancer through your telescope. The constellation is known as the Crab in English, and is a great region of the sky to seek out deep-sky objects that can be seen through a telescope. Nevertheless, there are still exciting targets to observe in Cancer, including one star that hosts its own planetary system.Ĭancer is a northern hemisphere constellation that can be found between Leo and Gemini.Ĭancer is also bordered by the constellations Lynx, Leo Minor, Canis Minor and Hydra. Yes, it contains the open cluster M44, also known as the Beehive Cluster (pinpointed by the asterisk in our chart above) and there’s another fainter open cluster near Acubens (Alpha (α) Cancri) called M67, but the stars that form the Zodiacal Crab of Cancer are pretty faint. As a constellation, it has to be said that Cancer isn’t one of the most impressive.
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