61 Virginis b (abbreviated 61 Vir b) is an

extrasolar planet An exoplanet or extrasolar planet is a planet outside the Solar System. The first possible evidence of an exoplanet was noted in 1917 but was not recognized as such. The first confirmation of detection occurred in 1992. A different planet, init ...

, orbiting the 5th

magnitude Magnitude may refer to: Mathematics *Euclidean vector, a quantity defined by both its magnitude and its direction *Magnitude (mathematics), the relative size of an object *Norm (mathematics), a term for the size or length of a vector *Order of ...

G-type star A G-type main-sequence star (Spectral type: G-V), also often, and imprecisely called a yellow dwarf, or G star, is a main-sequence star (luminosity class V) of spectral type G. Such a star has about 0.9 to 1.1 solar masses and an effective tempe ...

61 Virginis 61 Virginis (abbreviated 61 Vir) is the Flamsteed designation of a G-type main-sequence star (G7V) slightly less massive than the Sun (which has a hotter G2V spectral type), located about 27.9 light-years away in the constellation of Virg ...

, in

Virgo Virgo may refer to: *Virgo (astrology), the sixth astrological sign of the zodiac *Virgo (constellation), a constellation *Virgo Cluster, a cluster of galaxies in the constellation Virgo *Virgo Stellar Stream, remains of a dwarf galaxy *Virgo Supe ...

. This planet has a

minimum mass In astronomy, minimum mass is the lower-bound calculated mass of observed objects such as planets, stars and binary systems, nebulae, and black holes. Minimum mass is a widely cited statistic for extrasolar planets detected by the radial veloc ...

of 5.1 times that of Earth and is an example of a

super-Earth A super-Earth is an extrasolar planet with a mass higher than Earth's, but substantially below those of the Solar System's ice giants, Uranus and Neptune, which are 14.5 and 17 times Earth's, respectively. The term "super-Earth" refers only to ...

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 Doppler spectroscopy (also known as the radial-velocity method, or colloquially, the wobble method) is an indirect method for finding extrasolar planets and brown dwarfs from radial-velocity measurements via observation of Doppler shifts in t ...

taken at Keck and Anglo-Australian Observatories.

Characteristics

Mass, radius and temperature

61 Virginis b is a

, an exoplanet with a radius and mass bigger than Earth, but smaller than that of the ice giants

Neptune Neptune is the eighth planet from the Sun and the farthest known planet in the Solar System. It is the fourth-largest planet in the Solar System by diameter, the third-most-massive planet, and the densest giant planet. It is 17 times ...

and

Uranus Uranus is the seventh planet from the Sun. Its name is a reference to the Greek god of the sky, Uranus (mythology), Uranus (Caelus), who, according to Greek mythology, was the great-grandfather of Ares (Mars (mythology), Mars), grandfather ...

. It has an

equilibrium temperature The planetary equilibrium temperature is a theoretical temperature that a planet would be if it were a black body being heated only by its parent star. In this model, the presence or absence of an atmosphere (and therefore any greenhouse effect) is ...

of . It has an estimated

of around 5.1 , and a potential radius of 1.6 , based on its mass.

Host star

The planet orbits a ( G-type)

star A star is an astronomical object comprising a luminous spheroid of plasma (physics), plasma held together by its gravity. The List of nearest stars and brown dwarfs, nearest star to Earth is the Sun. Many other stars are visible to the naked ...

named

, orbited by a total of three planets. The star has a mass of 0.94 and a radius of 0.98 . It has a temperature of 5531 K and is about 8.96 billion years old. In comparison, the

Sun The Sun is the star at the center of the Solar System. It is a nearly perfect ball of hot plasma, heated to incandescence by nuclear fusion reactions in its core. The Sun radiates this energy mainly as light, ultraviolet, and infrared radi ...

is 4.6 billion years old and has a temperature of 5778 K. The star has slightly less metals then the Sun, with a

metallicity In astronomy, metallicity is the abundance of elements present in an object that are heavier than hydrogen and helium. Most of the normal physical matter in the Universe is either hydrogen or helium, and astronomers use the word ''"metals"'' as a ...

( e/H of −0.03, or 94% of the solar amount. Its luminosity () is 80% that of the Sun. The star's

apparent magnitude Apparent magnitude () is a measure of the brightness of a star or other astronomical object observed from Earth. An object's apparent magnitude depends on its intrinsic luminosity, its distance from Earth, and any extinction of the object's li ...

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

Orbit

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 Mercury commonly refers to: * Mercury (planet), the nearest planet to the Sun * Mercury (element), a metallic chemical element with the symbol Hg * Mercury (mythology), a Roman god Mercury or The Mercury may also refer to: Companies * Merc ...

's from the Sun, which is 0.38 AU). It receives 296.5 times more

sunlight Sunlight is a portion of the electromagnetic radiation given off by the Sun, in particular infrared, visible, and ultraviolet light. On Earth, sunlight is scattered and filtered through Earth's atmosphere, and is obvious as daylight when t ...

that Earth does from the Sun. The planet may be tidally locked meaning that there is a permanent day side and a permanent night side.

Discovery

The search for 61 Virginis b started when its host star was chosen an ideal target for a planet search using the

(in which the gravitational pull of a planet on its star is measured by observing the resulting

Doppler shift The Doppler effect or Doppler shift (or simply Doppler, when in context) is the change in frequency of a wave in relation to an observer who is moving relative to the wave source. It is named after the Austrian physicist Christian Doppler, who d ...

), as stellar activity would not overly mask or mimic

Doppler spectroscopy Doppler spectroscopy (also known as the radial-velocity method, or colloquially, the wobble method) is an indirect method for finding extrasolar planets and brown dwarfs from radial-velocity measurements via observation of Doppler shifts in t ...

measurements. It was also confirmed that 61 Virginis is neither a binary star nor a quickly rotating star, common

false positive A false positive is an error in binary classification in which a test result incorrectly indicates the presence of a condition (such as a disease when the disease is not present), while a false negative is the opposite error, where the test result ...

s when searching for transiting planets. Analysis of the resulting data found that the radial velocity variations most likely indicated the existence of a planet. The net result was an estimate of a 5.1 planetary companion orbiting the star at a distance of 0.05 AU with an eccentricity of 0.12. An attempt to determine if the planet transits its host star using the

Spitzer Space Telescope The Spitzer Space Telescope, formerly the Space Infrared Telescope Facility (SIRTF), was an infrared space telescope launched in 2003. Operations ended on 30 January 2020. Spitzer was the third space telescope dedicated to infrared astronomy, f ...

unfortunately failed due to technical issues related to the brightness of the star.

Look also at

List of star systems within 25–30 light-years This is a list of star systems within 25–30 light-years of Earth. See also * List of nearest stars and brown dwarfs * List of star systems within 20–25 light-years * List of star systems within 30-35 light-years * Lists of stars * List of ...

References

External links

* {{Virgo (constellation) 61 Virginis Exoplanets discovered in 2009 Super-Earths Exoplanets detected by radial velocity Virgo (constellation) Terrestrial planets