55 Cancri


Template: Infobox double star / Maintenance / single coordinate

55 Cancri (Bayer designation Rho1 Cancri ), in short: 55 Cnc, is a double star, which is about 41 light years away. It is located in the constellation Cancer at a right ascension of 08h 52m 35.8 s and a declination of 28 ° 19 ' 50.9 " ( equinox 2000.0 ). The system consists of the Yellow dwarf 55 Cancri A and the red dwarf star 55 Cancri B. With five known planet 55 Cancri is currently one of the largest planetary systems outside our solar system.

Physical Properties

55 Cancri A

55 Cancri A with a radius of 0.96 sun both slightly smaller radii, and fainter than the sun. Both stars belong to spectral class G, 55 Cancri A has but with a slightly later G8 subtype than the sun with G2. This small difference is due to the to the sun slightly cooler surface temperature of about 5300 ° C into existence ( 5570 ± 50K ). The star shows little or no variability and little charisma of its chromosphere. He is like the sun to the main sequence stars of luminosity class V. Consequently, they are situated in the stable phase of hydrogen burning. The deviations of the physical parameters between 55 Cancri A and the Sun are essentially due to the different stellar masses. This is also reflected in the position of the stars to each other reflected on the main sequence. The mass of 55 Cancri A is about 0.95 solar masses. Therefore, the star about 12 billion years, and thus almost a billion years is longer than the sun, stay in the main sequence.

At the end of his life, 55 Cancri A will consume its supply of hydrogen and reach the state of a red giant that will engulf the inner planets, and eventually end up as a white dwarf.

55 Cancri B

The 1065 AE of 55 Cancri A distant 55 Cancri B is a red dwarf star of spectral type M3. Its mass corresponds to 0.13 solar masses, and the diameter is 0.3 solar diameter. The resulting weak luminosity makes in about 1% of the luminosity of 55 Cancri A. Although it is not safe, there are signs that it itself is a binary star system 55 Cancri B.


55 Cancri A is orbited by at least five planets. They can be here in four inner and divide an outer planet. Your wording was - as usual - in the order of their discovery: 55 Cancri b,- c,- d ,-e and -f.

With increasing distance from their central star, there are:

55 Cancri e

55 Cancri e is an extrasolar planet whose mass (0.034 Jupiter masses) is located exactly on the boundary between gas giants and terrestrial planets. So it could be that this planet is a kind of " super-Earth " is. He moves in just 18 hours to its star, with an eccentricity of 0.07. The surface is probably dominated by volcanoes and lava flows, if the planet has a solid surface.

Even if the planet is an Earth-like, he is far too close to its star than that life could exist on it with a distance of only 0.016 astronomical units. The surface temperature should be at this distance 1200.degree. 55 Cancri e was discovered in 2004.

55 Cancri b

The planet 55 Cancri b was discovered in 1996 as the first planet of the system. Its mass is approximately 0.82 Jupiter masses. Its orbit has a semimajor axis of 0.115 AU and an eccentricity of 0.014. The orbital period is 14.65 days.

55 Cancri c

Main article: 55 Cancri c

The planet 55 Cancri c was discovered in 2002. Its mass corresponds to 0.16 Jupiter masses, it is slightly smaller than Saturn. His near-circular orbit (eccentricity of about 0.086 ) has a semi-major axis of 0.24 AU. This corresponds to an orbital period of 44.34 days.

55 Cancri f

On 6 November 2007 an American team of astronomers has discovered 55 Cancri f the fifth planet around 55 Cancri A. On it, there could be liquid water, since it lies in the habitable zone. However, he is probably a gas giant, but it could have orbiting moons that could have a solid surface.

The newly discovered planet is about half the mass of our Saturn and orbits its sun 55 Cancri A in 260 days.

55 Cancri d

The planet 55 Cancri d was discovered in 2002. Its mass is about 3.8 Jupiter masses. 55 Cancri d is more massive than the other four planets together and could play a similar stabilizing role for the planetary system play like Jupiter in our solar system. With a semi-major axis of 5.77 AU with an eccentricity of about 0.025 is 55 Cancri d also almost the same distance as Jupiter. The orbital period is about 5218 days.