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55 Cancri (Rho1 Cancri)


Comparison of the 55 Cancri system and our own solar system
Comparison of the solar system with the 55 Cancri system
Credit: NASA
A visual binary star system in the constellation Cancer consisting of a middle-aged, Sun-like primary of high metallicity, 55 Cancri A, and a red dwarf companion, 55 Cancri B. (55 Cancri is the star's Flamsteed designation. Its Bayer designation is Rho1 Cancri.) The component stars are separated by a mean distance of about 1,150 astronomical units (172 billion km, or 108 billion miles). In orbit around the primary have been discovered four planets, Ab, Ac, Ad, and Ae. This is the largest number of planets currently known to exist around a star other than the Sun. The most recently discovered of the quartet, Ae, is also one of the new "Neptune-class" extrasolar planets announced in 2004.

Ae, the innermost planet, is only about 14 times as massive as the Earth but moves in a tiny orbit that must result in an extremely high surface temperature. Ab, the second planet, is an epistellar jovian, or "hot Jupiter," only the fourth extrasolar planet of all to be discovered; it circles the host star at less than one third the distance of Mercury from the Sun. The third planet, Ac, is a Saturn-sized world in a highly elliptical orbit that takes it well within intra-Mercurian distance of the star. The fourth planet, Ae, is a high-mass classical jovian.

Also surrounding 55 Cancri A is a dust disk, which is presumably a regenerated disk, extending out to about 40 astronomical units from the star with an inclination of about 25°.3, 4, 5

55 Cnc was one of the five targets of the Feb. 14, 2003 "Cosmic Call" initiative (see interstellar radio messages).


Host star (55 Cancri A)
distance 40.9 light-years (12.5 pc)
spectral type G8 V
temperature 4,980°C (5,250 K)
luminosity (Sun = 1) 0.61
mass (Sun = 1) 0.95
apparent magnitude 5.95


Planets
  Ae Ab Ac Ad
mass (Jupiter = 1) 0.045 0.78 0.22 3.92
semimajor axis 0.038 AU 0.115 AU 0.240 AU 5.26 AU
orbital period 2.81 days 14.7 days 43.9 days 12.4 years
eccentricity 0.17 0.02 0.44 0.33
year of discovery 2004 1997 2002 2002
discoverer G. Marcy et al7 G. Marcy et al2 G. Marcy et al6 G. Marcy et al6
method of discovery radial velocity radial velocity radial velocity radial velocity


References

  1. Gonzalez, G., and Vanture, A. "Parent Stars of Extrasolar Plnets III: Rho1 Cancri Revisited," Astronomy & Astrophysics, 339, L29 (1998).
  2. Butler, P., Marcy, G., Williams, E., Hauser, H., and Shirts, P. "Three New 51 Peg-type Planets," Astrophysical Journal Letters, 474, L115 (1997).
  3. Baliunas, S., Henry, G. W., Donahue, R. A., Fekel, F. C., and Soon, W. H. "Properties of Sunlike Stars with Planets," Astrophysical Journal Letters, 474, L119 (1997).
  4. Dominik, C., Laureijs, R. J., Jourdain de Mouizon, M., and Habing, H. J. "A Vega-like Disk Associated with the Planetary System of Rho1 Cancri," Astronomy & Astrophysics, 329, L53 (1998).
  5. Trilling, D., and Brown, R. "A Circumstellar Dust Disk Around a Star with a Known Planetary Companion," Nature, 395, 775 (1998).
  6. Marcy G., Butler, P., Fischer D., Laughlin G., Vogt S., Henry G., and Pourbaix D. "A Planet at 5 AU Around 55 Cancri," ApJ., 581, 1375 (2002).
  7. McArthur B., Endl M., Cochran W., Benedict F., Fischer D., Marcy G., Butler P., Naef D., Mayor M;, Queloz D., Udry S., and Harrison T. "Detection of a Neptune-Mass Planet in the 55 Cancri System by the HET," ApJ. Letters, accepted (2004).

Related categories

   • EXTRASOLAR PLANETS AND SUBSTELLAR OBJECTS
   • NOTABLE STARS




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