55 Cancri b
| Extrasolar planet | List of extrasolar 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) | 0.115 ± 0.0000011[1] AU (17.2 Gm) |
| 9.18 mas | ||
| Periastron | (q) | 0.113 AU (16.9 Gm) |
| Apastron | (Q) | 0.116 AU (17.4 Gm) |
| Eccentricity | (e) | 0.014 ± 0.008[1] |
| Orbital period | (P) | 14.65162 ± 0.0007[1] d (0.04011325 y) |
| Inclination | (i) | ~85[2][3]° |
| Argument of periastron |
(ω) | 131.94 ± 30[1]° |
| Time of periastron | (T0) | 2,450,002.94749 ± 1.2[1] JD |
| Semi-amplitude | (K) | 71.32 ± 0.41[1] m/s |
| Physical characteristics | ||
| Mass | (m) | 0.824 ± 0.007[1][2] MJ |
| Stellar flux | (F⊙) | 48 ⊕ |
| Discovery information | ||
| Discovery date | April 12, 1996 | |
| Discoverer(s) | Butler, Marcy | |
| Discovery method | Radial velocity | |
| Other detection methods | Transit | |
| Discovery site | California, USA | |
| Discovery status | Published | |
| Other designations | ||
| 55 Cancri Ab, Rho1 Cancri b, HD 75732 b | ||
| Database references | ||
| Extrasolar Planets Encyclopaedia | data | |
| SIMBAD | data | |
| Exoplanet Archive | data | |
| Open Exoplanet Catalogue | data | |
55 Cancri b (abbreviated 55 Cnc b and occasionally referred to as 55 Cancri Ab in order to distinguish it from the star 55 Cancri B) is an extrasolar planet orbiting the Sun-like star 55 Cancri A every 14.65 days. It is the second planet in order of distance from its star, and is an example of a hot Jupiter, or possibly rather "warm Jupiter".[4] Discovered in 1996 by Geoffrey Marcy and R. Paul Butler, 55 Cancri b was the fourth known extrasolar planet, excluding pulsar planets.
Discovery
Like the majority of known extrasolar planets, 55 Cancri b was discovered by detecting variations in its star's radial velocity caused by the planet's gravity. By making sensitive measurements of the Doppler shift of the spectrum of 55 Cancri A, a 15-day periodicity was detected. The planet was announced in 1996, together with the planet of Tau Boötis and the innermost planet of Upsilon Andromedae.[5]
Even when this inner planet, with a mass at least 78% times that of Jupiter was accounted for, the star still showed a drift in its radial velocity. This eventually led to the discovery of the outer planet 55 Cancri d in 2002.
Orbit and mass
55 Cancri b is in a short-period orbit, though not so extreme as that of the previously detected hot Jupiter 51 Pegasi b. The orbital period indicates that the planet is located close to a 1:3 mean motion resonance with 55 Cancri c, however investigations of the planetary parameters in a Newtonian simulation indicate that while the orbital periods are close to this ratio, the planets are not actually in the resonance.[1]
In 2012, b's upper atmosphere was observed transiting the star; so its inclination is about 85 degrees, coplanar with e. This helped to constrain the mass of the planet but the inclination was too low to constrain its radius.[2]
The mass is about .85 that of Jupiter.[2]
Characteristics
55 Cancri b is a gas giant with no solid surface. The atmospheric transit has demonstrated hydrogen in the upper atmosphere.[2]
That transit is so tangential, that properties such as its radius, density, and temperature are unknown. Assuming a composition similar to that of Jupiter and that its environment is close to chemical equilibrium, 55 Cancri b's upper atmosphere is predicted to be cloudless with a spectrum dominated by alkali metal absorption.[6]
The atmosphere's transit indicates that it is slowly evaporating under the sun's heat. The evaporation is slower than that for previously studied (hotter) hot Jupiters.[4]
The planet is unlikely to have large moons, since tidal forces would either eject them from orbit or destroy them on short timescales relative to the age of the system.[7]
See also
- Appearance of extrasolar planets
References
- ↑ 1.0 1.1 1.2 1.3 1.4 1.5 1.6 1.7 DA Fischer et al. (March 2008). "Five Planets Orbiting 55 Cancri". Astrophysical Journal 675 (675): 790–801. arXiv:0712.3917. Bibcode:2008ApJ...675..790F. doi:10.1086/525512.
- ↑ 2.0 2.1 2.2 2.3 2.4 D. Ehrenreich et al. (October 2, 2012). "Hint of a transiting extended atmosphere on 55 Cancri b". Astronomy & Astrophysics. arXiv:1210.0531. Bibcode:2012A&A...547A..18E. doi:10.1051/0004-6361/201219981.
- ↑ D. Dragomir, 2012-08-27, referred to in Ehrenreich
- ↑ 4.0 4.1 "Astrophile: First puffy, 'warm Jupiter' spotted - space - 12 October 2012". New Scientist. Retrieved 2012-11-09.
- ↑ Butler; Marcy, Geoffrey W.; Williams, Eric; Hauser, Heather; Shirts, Phil et al. (1997). "Three New 51 Pegasi-Type Planets". The Astrophysical Journal 474 (2): L115–L118. Bibcode:1997ApJ...474L.115B. doi:10.1086/310444.
- ↑ Sudarsky, D. et al. (2003). "Theoretical Spectra and Atmospheres of Extrasolar Giant Planets". The Astrophysical Journal 588 (2): 1121–1148. arXiv:astro-ph/0210216. Bibcode:2003ApJ...588.1121S. doi:10.1086/374331.
- ↑ Barnes, J., O'Brien, D. (2002). "Stability of Satellites around Close-in Extrasolar Giant Planets". The Astrophysical Journal 575 (2): 1087–1093. arXiv:astro-ph/0205035. Bibcode:2002ApJ...575.1087B. doi:10.1086/341477.
External links
- Jean Schneider (2011). "Notes for Planet 55 Cnc b". Extrasolar Planets Encyclopaedia. Retrieved 8 October 2011.
Coordinates: 
08h 52m 35.8s, +28° 19′ 51″
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