55 Cancri f

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55 Cancri f
Extrasolar planet List of extrasolar planets
Artist's concept shows four of the five planets that orbit 55 Cancri, a star much like our own.jpg
An artist's impression of 55 Cancri f.
The star-like-looking dots around its sun are the three innermost planets.
Parent star
Star 55 Cancri A
Constellation Cancer
Right ascension (α) 08h 52m 35.8s
Declination (δ) +28° 19′ 51″
Apparent magnitude (mV) 5.95
Distance 40.3 ± 0.4 ly
(12.3 ± 0.1 pc)
Spectral type G8V
Mass (m) 0.95 ± 0.10 M
Radius (r) 1.152 ± 0.035 R
Temperature (T) 5373 ± 9.7 K
Metallicity [Fe/H] 0.29
Age 7.4–8.7 Gyr
Orbital elements
Semimajor axis (a) 0.781 ± 0.007[1] AU
(116.9 Gm)
    62.5 mas
Periastron (q) 0.730 AU
(109.1 Gm)
Apastron (Q) 0.833 AU
(124.6 Gm)
Eccentricity (e) 0.2 ± 0.2[1]
Orbital period (P) 260.00 ± 1.1[1] d
(0.7118 y)
Argument of
periastron
(ω) 181.1 ± 60[1]°
Time of periastron (T0) 2,450,080.9108 ± 1.1[1] JD
Semi-amplitude (K) 4.879 ± 0.6[1] m/s
Physical characteristics
Minimum mass (m sin i) 0.144 ± 0.04[1] MJ
(45.7 ± 12.7[1] M)
Stellar flux (F) ~1
Discovery information
Discovery date 11 April 2005 (announced)
6 November 2007 (published)
Discoverer(s) announced by J. Wisdom
published by D. Fischer
Discovery method Doppler spectroscopy
Discovery site  United States
Discovery status Published
Other designations
55 Cancri Af, Rho1 Cancri f, HD 75732 f
Database references
Extrasolar Planets
Encyclopaedia
data
SIMBAD data

55 Cancri f (abbreviated 55 Cnc f and also referred to as Rho1 Cancri f) is an extrasolar planet approximately 41 light-years away from Earth in the constellation of Cancer (the Crab). 55 Cancri f is the fourth known planet (in order of distance) from the star 55 Cancri and the first planet to have been given the designation of "f".[2]

Discovery[edit]

Radial velocity changes over time of 55 Cancri caused by the orbit of 55 Cancri f.

The initial presentation of this planet occurred at a meeting of the American Astronomical Society in April 2005,[3] however it was another two and a half years before the planet was to be published in a peer-reviewed journal.[1] It is the first known planet outside our solar system to spend its entire orbit within what astronomers call the "habitable zone".[4] Furthermore, its discovery made 55 Cancri the first star other than the Sun known to have at least five planets.

Orbit and mass[edit]

55 Cnc f's orbit compared to the orbit of Venus (0.72AU).

55 Cancri f is located about 0.781 AU away from the star and takes 260 days to complete a full orbit.[5] A limitation of the radial velocity method used to detect 55 Cancri f is that only a minimum mass can be obtained, in this case around 0.144 times that of Jupiter, or half the mass of Saturn.[5] A Keplerian fit to the radial velocity data of 55 Cancri A indicates that the orbit is consistent with being circular, however changing the value in a range between 0 and 0.4 does not significantly alter the chi-squared statistic of the fit, thus a representative eccentricity of 0.2±0.2 was assumed.[1] In a Newtonian model which takes interactions between the planets into account, the eccentricity comes out as 0.0002, almost perfectly circular.[1]

Astrometric observations made with the Hubble Space Telescope suggest that the outer planet 55 Cancri d is inclined at 53° with respect to the plane of the sky.[6] The inner planets b and e are inclined at 85°. The inclination of f is unknown.

Characteristics[edit]

Since the planet was detected indirectly through observations of its star, properties such as its radius, composition and temperature are unknown. With a mass half that of Saturn,[5] 55 Cancri f is likely to be a gas giant with no solid surface. It orbits in the so-called "habitable zone," which means that liquid water could exist on the surface of a possible moon.[4]

It is not known if the composition and appearance is more like Saturn or Neptune.[2] Based on its temperature, it should be a Sudarsky Class II planet, covered in water clouds.[citation needed]

References[edit]

  1. ^ a b c d e f g h i j k Debra A. Fischer, Geoffrey W. Marcy, R. Paul Butler, Steven S. Vogt, Greg Laughlin, Gregory W. Henry, David Abouav, Kathryn M. G. Peek, Jason T. Wright, John A. Johnson, Chris McCarthy, Howard Isaacson (23 December 2007). "Five Planets Orbiting 55 Cancri". Astrophysics 675: 790–801. arXiv:0712.3917. Bibcode:2008ApJ...675..790F. doi:10.1086/525512. 
  2. ^ a b Shige Abe (12 November 2007). "Researchers Identify First Five-Planet Extrasolar System". NASA Astrobiology. Archived from the original on 16 September 2008. Retrieved 17 September 2008. 
  3. ^ J. Wisdom (11 April 2005). "A Neptune-sized Planet in the rho1 Cancri System". DDA 36th Meeting, 10–14 April 2005—Session 5 Posters (The American Astronomical Society). Archived from the original on 16 December 2006. Retrieved 17 September 2008. 
  4. ^ a b Ian Sample, science correspondent (7 November 2007). "Could this be Earth's near twin? Introducing planet 55 Cancri f". London: The Guardian. Archived from the original on 2 October 2008. Retrieved 17 October 2008. 
  5. ^ a b c Jean Schneider (2011). "Notes for Planet 55 Cnc f". Extrasolar Planets Encyclopaedia. Retrieved 8 October 2011. 
  6. ^ Han et al. (2001). "Preliminary Astrometric Masses for Proposed Extrasolar Planetary Companions". The Astrophysical Journal Letters 548 (1): L57–L60. Bibcode:2001ApJ...548L..57H. doi:10.1086/318927. 

External links[edit]

Coordinates: Sky map 08h 52m 35.8s, +28° 19′ 51″