61 Virginis b

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61 Virginis b
Exoplanet List of exoplanets
Artist concept 61vir b.png
Artist's impression of 61 Virginis b as a hot super-Earth, with some sporadic volcanic activity.
Parent star
Star 61 Virginis
Constellation Virgo
Right ascension (α) 13h 18m 24.3s
Declination (δ) −18° 18′ 40.3″
Apparent magnitude (mV) 4.74
Distance 27.8±0.2 ly
(8.52±0.05 pc)
Spectral type G5V
Mass (m) 0.942+0.034
Radius (r) 0.98 (± 0.03) R
Temperature (T) 5531 K
Metallicity [Fe/H] −0.02
Age 8.96+2.76
Physical characteristics
Minimum mass (m sin i) 5.1 (± 0.5)[1] M
Radius (r) ~1.6 R
Stellar flux (F) 296.5[2]
Temperature (T) 1,054 K (781 °C; 1,438 °F)
Orbital elements
Semi-major axis (a) 0.050201±0.000005 AU
(7.5100 Gm)
Periastron (q) 0.044239 AU
(6.6181 Gm)
Apastron (Q) 0.056163 AU
(8.4019 Gm)
Eccentricity (e) 0.12±0.11
Orbital period (P) 4.2150±0.0006 d
    (101.16 h)
Orbital speed (υ) 130.01 km/s
Argument of
(ω) 105±54°
Time of periastron (T0) 2453369.166 JD
Discovery information
Discovery date 14 December 2009
Discoverer(s) Vogt et al.
Discovery method Radial velocity
Discovery site Keck Observatory
Anglo-Australian Observatory
Discovery status Confirmed[3]
Database references
Extrasolar Planets
Exoplanet Archive data
Open Exoplanet Catalogue data

61 Virginis b (abbreviated 61 Vir b) is an extrasolar planet, orbiting the 5th magnitude G-type star 61 Virginis, in Virgo. This planet has a minimum mass of 5.1 times that of Earth and is an example of a super-Earth planet. It orbits very close to the star, at a distance of 0.050201 AU with an eccentricity of 0.12. This planet was discovered on 14 December 2009 using the radial velocity method taken at Keck and Anglo-Australian Observatories.[1][4]


Mass, radius and temperature[edit]

61 Virginis b is a super-Earth, an exoplanet with a radius and mass bigger than Earth, but smaller than that of the ice giants Neptune and Uranus. It has an equilibrium temperature of 1,054 K (781 °C; 1,438 °F).[2] It has an estimated minimum mass of around 5.1 M, and a potential radius of 1.6 R, based on its mass.

Host star[edit]

The planet orbits a (G-type) star named 61 Virginis, orbited by a total of three planets.[1] The star has a mass of 0.94 M and a radius of 0.98 R. It has a temperature of 5531 K and is about 8.96 billion years old.[1] In comparison, the Sun is 4.6 billion years old[5] and has a temperature of 5778 K.[6] The star has slightly less metals then the Sun, with a metallicity ([Fe/H]) of −0.03, or 94% of the solar amount.[1] Its luminosity (L) is 80% that of the Sun.[1]

The star's apparent magnitude, or how bright it appears from Earth's perspective, is 4.74. Therefore, it can be seen with the naked eye.


61 Virginis b orbits its host star with an orbital period of 4.21 days at a distance of about 0.05 AU (compared to Mercury's from the Sun, which is 0.38 AU). It receives 296.5 times more sunlight that Earth does from the Sun.[2]


The search for 61 Virginis b started when its host star was chosen an ideal target for a planet search using the radial velocity method (in which the gravitational pull of a planet on its star is measured by observing the resulting Doppler shift), as stellar activity would not overly mask or mimic Doppler spectroscopy measurements. It was also confirmed that 61 Virginis is neither a binary star nor a quickly rotating star, common false positives when searching for transiting planets.

Analysis of the resulting data found that the radial velocity variations most likely indicated the existence of a planet.[1] The net result was an estimate of a 5.1 M planetary companion orbiting the star at a distance of 0.05 AU with an eccentricity of 0.12.

See also[edit]


  1. ^ a b c d e f g Vogt, Steven (2009). "A Super-Earth and two Neptunes Orbiting the Nearby Sun-like star 61 Virginis". arXiv:0912.2599v1Freely accessible [astro-ph.EP]. 
  2. ^ a b c http://www.hpcf.upr.edu/~abel/phl/hec_plots/hec_orbit/hec_orbit_61_Vir_b.png
  3. ^ M. C. Wyatt; et al. (2012). "Herschel imaging of 61 Vir: implications for the prevalence of debris in low-mass planetary systems". MNRAS. arXiv:1206.2370Freely accessible. Bibcode:2012MNRAS.424.1206W. doi:10.1111/j.1365-2966.2012.21298.x. 
  4. ^ Tim Stephens (2009-12-14). "New planet discoveries suggest low-mass planets are common around nearby stars". UCSC News. UC Santa Cruz. Archived from the original on 23 December 2009. Retrieved 2009-12-14. 
  5. ^ Fraser Cain (16 September 2008). "How Old is the Sun?". Universe Today. Retrieved 19 February 2011. 
  6. ^ Fraser Cain (15 September 2008). "Temperature of the Sun". Universe Today. Retrieved 19 February 2011. 

External links[edit]

Coordinates: Sky map 13h 18m 24.3s, −18° 18′ 40.3″