55 Cancri f
 An artist's impression of 55 Cancri f. The three bright dots near its star are the three innermost planets. | |
| Discovery | |
|---|---|
| Discovered by | announced by J. Wisdom published by D. Fischer |
| Discovery site |  United States |
| Discovery date | 11 April 2005 (announced) 6 November 2007 (published) |
| Doppler spectroscopy | |
| Orbital characteristics | |
| Apastron | 0.833 AU (124,600,000 km) |
| Periastron | 0.730 AU (109,200,000 km) |
| 0.781 ± 0.007 AU (116,800,000 ± 1,000,000 km)[1] | |
| Eccentricity | 0.2 ± 0.2[1] |
| 260.00 ± 1.1[1] d 0.7118 y | |
| 2,450,080.9108 ± 1.1[1] | |
| 181.1 ± 60[1] | |
| Semi-amplitude | 4.879 ± 0.6[1] |
| Star | 55 Cancri A |
| Physical characteristics | |
| Temperature | 200–300 K (−73–27 °C; −100–80 °F) |
55 Cancri f (abbreviated 55 Cnc f), also designated Rho1 Cancri f and formally named Harriot /ˈhæriət/,[2] 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".[3]
Name
In July 2014 the International Astronomical Union launched a process for giving proper names to certain exoplanets and their host stars.[4] The process involved public nomination and voting for the new names.[5] In December 2015, the IAU announced the winning name was Harriot for this planet.[6] The winning name was submitted by the Royal Netherlands Association for Meteorology and Astronomy of the Netherlands. It honors the astronomer Thomas Harriot.[7]
Discovery
The initial presentation of this planet occurred at a meeting of the American Astronomical Society in April 2005,[8] 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".[9] Furthermore, its discovery made 55 Cancri the first star other than the Sun known to have at least five planets.
Orbit and mass
55 Cancri f is located about 0.781 AU away from the star and takes 262 days to complete a full orbit.[10] 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.[10] 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.[11] The inner planets b and e are inclined at 85°. The inclination of f is unknown.
Characteristics
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,[10] 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.[9]
It is not known if the composition and appearance is more like that of Saturn or Neptune.[3] Based on its temperature, it could be a Sudarsky Class II planet, covered in water clouds, or a Sudarsky Class III with no clouds and a dark azure color.[citation needed]
References
- ^ a b c d e f g h i Debra A. Fischer; Geoffrey W. Marcy; R. Paul Butler; Steven S. Vogt; Greg Laughlin; Gregory W. Henry; et al. (23 December 2007). "Five Planets Orbiting 55 Cancri". Astrophysical Journal. 675: 790–801. arXiv:0712.3917. Bibcode:2008ApJ...675..790F. doi:10.1086/525512.
- ^ Mathematics Pronunciation Guide
- ^ 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.
- ^ NameExoWorlds: An IAU Worldwide Contest to Name Exoplanets and their Host Stars. IAU.org. 9 July 2014
- ^ NameExoWorlds The Process
- ^ Final Results of NameExoWorlds Public Vote Released, International Astronomical Union, 15 December 2015.
- ^ NameExoWorlds The Approved Names
- ^ 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.
- ^ a b Ian Sample, science correspondent (7 November 2007). "Could this be Earth's near twin? Introducing planet 55 Cancri f". The Guardian. London. Archived from the original on 2 October 2008. Retrieved 17 October 2008.
{{cite news}}:|author=has generic name (help) - ^ a b c Jean Schneider (2011). "Notes for Planet 55 Cnc f". Extrasolar Planets Encyclopaedia. Retrieved 8 October 2011.
- ^ 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
- Ward Glen (8 November 2007). "Astronomers Find Fifth Planet Around 55 Cancri". The Starry Mirror. Archived from the original on 10 November 2007. Retrieved 17 September 2008.
