- 55 Cancri f
name = 55 Cancri fPlanetbox image
caption = An artist's impression of 55 Cancri f.
The stars around its sun are the three innermost planets.Planetbox star
star = 55 Cancri A
constell = Cancer
RA = RA|08|52|35.8
DEC = DEC|+28|19|51
dist_ly = 40.9
dist_pc = 12.5
class = G8VPlanetbox orbit
semimajor = 0.781 ± 0.007cite journal|url=http://arxiv.org/abs/0712.3917 |journal= Astrophysics |title=Five Planets Orbiting 55 Cancri| author=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| date=2007-12-23 |accessdate=2008-09-17]
eccentricity = 0.2 ± 0.2
period = 260.00 ± 1.1
ang_dist = 58.3
long_peri = 181.1 ± 60
t_peri = 2,450,080.9108 ± 1.1
semi-amp = 4.879 ± 0.6Planetbox character
mass = >0.144 ± 0.04Planetbox discovery
11 April 2005(announced) 6 November 2007(published)
discoverers = J. Wisdom
discovery_site = flag|United States
discovery_status = PublishedPlanetbox catalog
names = Rho1 Cancri f, HD 75732 f
55 Cancri f, also referred to as Rho1 Cancri f, is an
extrasolar planetapproximately 41 light-years away in the constellationof Cancer (the Crab). 55 Cancri f is the fourth known planet (in order of distance) from the star 55 Cancriand the first planet to have been given the designation of "f". [cite web|url=http://astrobiology.nasa.gov/articles/researchers-identify-first-five-planet-extrasolar-system/ |title=Researchers Identify First Five-Planet Extrasolar System |publisher= NASA Astrobiology |date=2007-11-12|author=Shige Abe |accessdate=2008-09-17] As of September 2008, this makes 55 Cancri the only planetary systemoutside the Solar Systemthat is known to contain at least 5 planets. [cite web|url=http://exoplanet.eu/catalog-all.php |title=The Extrasolar Planets Encyclopaedia |publisher=Exoplanet.eu |date= |accessdate=2008-09-14]
The initial presentation of this planet occurred at a meeting of the
American Astronomical Societyin April 2005, [cite journal |author=J. Wisdom |url=http://www.aas.org/publications/baas/v37n2/dda05/29.htm |archiveurl=http://web.archive.org/web/20061216012023/http://www.aas.org/publications/baas/v37n2/dda05/29.htm |archivedate=2006-12-16 |title=A Neptune-sized Planet in the rho1 Cancri System |accessdate=2008-09-17 |publisher=The American Astronomical Society |date=2005-04-11| journal=DDA 36th Meeting, 10-14 April 2005—Session 5 Posters] however it was another two and a half years before the planet was to be published in a peer-reviewed journal. Unlike the majority of known extrasolar planets, 55 Cancri f was detected by a third party, by reviewing already-published data on the star and analyzing observed changes in its radial velocity(obtained by measuring of the Doppler shiftof the star's spectrum).
Orbit and mass
55 Cancri f is located about 0.781 AU away from the star which takes 260 days to complete.cite web|url=http://exoplanet.eu/planet.php?p1=55+Cnc&p2=f |title=Notes for Planet 55 Cnc f |publisher="The Extrasolar Planets Encyclopaedia"|date= |accessdate=2008-09-14] A limitation of the radial velocity method used to detect 55 Cancri f is that only a
minimum masscan be obtained, in this case around 0.144 times that of Jupiter, or 2.67 times the mass of Neptune. 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-square statisticof the fit, thus a representative eccentricity of 0.2±0.2 was assumed. In a Newtonian model which takes interactions between the planets into account, the eccentricity comes out as 0.0002, almost circular.
Astrometric observations made with the
Hubble Space Telescopesuggest that the outer planet 55 Cancri dis inclined at 53° with respect to the plane of the sky. [cite journal |url=http://www.obspm.fr/encycl/papers/mas_caps_final_formated.pdf |author=Han, I. et al.|title=Preliminary Astrometric Masses for Proposed Extrasolar Planetary Companions|journal= Astrophysical Journal|volume=548|pages=L57 – L60|year=2001|doi=10.1086/318927] If these measurements are confirmed and the system is assumed to be coplanar, the true massof the planet would therefore be about 25% greater than this lower limit, at around 0.18 Jupiter mass.
Since the planet was detected indirectly through observations of its star, properties such as its
radius, composition and temperatureare unknown. With a mass half that of Saturn, 55 Cancri f is likely to be a gas giantwith 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. [cite web|url=http://www.guardian.co.uk/science/2007/nov/07/spaceexploration |title=Could this be Earth's near twin? Introducing planet 55 Cancri f |publisher="The Guardian" |author=Sample, Ian |date=2007-11-07 |accessdate=2008-09-17]
55 Cancri b
55 Cancri c
55 Cancri d
55 Cancri e
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