55 Cancri f
| Exoplanet | List of exoplanets | |
|---|---|---|
 The three bright dots near its star are the three innermost planets. |
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| 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) |
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| 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 | ||
| Semi-major axis | (a) | 0.781 ± 0.007AU (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 |
| Orbital period | (P) | 260.00 ± 1.1d (0.7118 y) |
| Argument of periastron |
(ω) | 181.1 ± 60° |
| Time of periastron | (T0) | 2,450,080.9108 ± 1.1JD |
| Semi-amplitude | (K) | 4.879 ± 0.6m/s |
| Physical characteristics | ||
| Minimum mass | (m sin i) | 0.144 ± 0.04MJ (45.7 ± 12.7M⊕) |
| Stellar flux | (F⊙) | ~1 ⊕ |
| Temperature | (T) | 200–300 K (−73–27 °C; −100–80 °F) |
| Discovery information | ||
| Discovery date | 11 April 2005 (announced) 6 November 2007 (published) |
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| Discoverer(s) | announced by J. Wisdom published by D. Fischer |
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| Discovery method | Doppler spectroscopy | |
| Discovery site |
 United States
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| Discovery status | Published | |
| Other designations | ||
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Harriot, 55 Cancri Af, Rho1 Cancri f, HD 75732 f
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| Database references | ||
| Extrasolar Planets Encyclopaedia |
data | |
| SIMBAD | data | |
| Exoplanet Archive | data | |
| Open Exoplanet Catalogue | data | |
55 Cancri f (abbreviated 55 Cnc f), also designated Rho1 Cancri f and named Harriot, 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".
In July 2014 the International Astronomical Union launched a process for giving proper names to certain exoplanets and their host stars. The process involved public nomination and voting for the new names. In December 2015, the IAU announced the winning name was Harriot for this planet. The winning name was submitted by the Royal Netherlands Association for Meteorology and Astronomy of the Netherlands. It honors the astronomer Thomas Harriot.
The initial presentation of this planet occurred at a meeting of the American Astronomical Society in April 2005, however it was another two and a half years before the planet was to be published in a peer-reviewed journal. It is the first known planet outside our solar system to spend its entire orbit within what astronomers call the "habitable zone". Furthermore, its discovery made 55 Cancri the first star other than the Sun known to have at least five planets.
55 Cancri f is located about 0.781 AU away from the star and takes 262 days to complete a full orbit. 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. 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. In a Newtonian model which takes interactions between the planets into account, the eccentricity comes out as 0.0002, almost perfectly circular.
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