61 Virginis (abbreviated 61 Vir) is the

Flamsteed designation A Flamsteed designation is a combination of a number and constellation name that uniquely identifies most naked eye stars in the modern constellations visible from southern England. They are named for John Flamsteed who first used them while co ...

of a

G-type main-sequence 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 temp ...

(G7V) slightly less massive than 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 ...

(which has a hotter G2V spectral type), located about 27.9 light-years away in the

constellation A constellation is an area on the celestial sphere in which a group of visible stars forms Asterism (astronomy), a perceived pattern or outline, typically representing an animal, mythological subject, or inanimate object. The origins of the e ...

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 ...

. The composition of this star is nearly identical to the Sun. 61 Virginis (G7V) is the first well-established

main-sequence In astronomy, the main sequence is a continuous and distinctive band of stars that appears on plots of stellar color versus brightness. These color-magnitude plots are known as Hertzsprung–Russell diagrams after their co-developers, Ejnar Hert ...

star very similar to the Sun with a potential

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 ...

, though it was preceded by

COROT-7 CoRoT-7 (TYC 4799-1733-1) is a binary star system. The primary, CoRoT-7A is a G-type main sequence star, slightly smaller, cooler, and younger than the Sun. It has an apparent magnitude of 11.67, fainter than Proxima Centauri (mag. 11 ...

(a borderline

orange dwarf A K-type main-sequence star, also referred to as a K-type dwarf or an orange dwarf, is a main-sequence (hydrogen-burning) star of spectral type K and luminosity class V. These stars are intermediate in size between red M-type main-sequence stars ...

Description

61 Virginis is a fifth-

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 ...

with a

stellar classification In astronomy, stellar classification is the classification of stars based on their stellar spectrum, spectral characteristics. Electromagnetic radiation from the star is analyzed by splitting it with a Prism (optics), prism or diffraction grati ...

of G7 V. It is faint but visible to the naked eye south and east of the bright star

Spica Spica is the brightest object in the constellation of Virgo and one of the 20 brightest stars in the night sky. It has the Bayer designation α Virginis, which is Latinised to Alpha Virginis and abbreviated Alpha Vir or α Vir. Analys ...

in the

zodiac The zodiac is a belt-shaped region of the sky that extends approximately 8° north or south (as measured in celestial latitude) of the ecliptic, the Sun path, apparent path of the Sun across the celestial sphere over the course of the year. ...

. The designation 61 Virginis originated in the star catalogue of English astronomer

John Flamsteed John Flamsteed (19 August 1646 – 31 December 1719) was an English astronomer and the first Astronomer Royal. His main achievements were the preparation of a 3,000-star catalogue, ''Catalogus Britannicus'', and a star atlas called ''Atlas Coe ...

, as part of his ''Historia Coelestis Britannica''. An 1835 account of Flamsteed's work by English astronomer

Francis Baily Francis Baily (28 April 177430 August 1844) was an English astronomer. He is most famous for his observations of "Baily's beads" during a total eclipse of the Sun. Baily was also a major figure in the early history of the Royal Astronomical S ...

noted that the star showed a

proper motion Proper motion is the astrometric measure of the observed changes in the apparent places of stars or other celestial objects in the sky, as seen from the center of mass of the Solar System, compared to the abstract background of the more dista ...

. This made the star of interest for parallax studies, and by 1950 a mean annual value of 0.006″ was obtained. The present day result, obtained with data from the

Hipparcos ''Hipparcos'' was a scientific satellite of the European Space Agency (ESA), launched in 1989 and operated until 1993. It was the first space experiment devoted to precision astrometry, the accurate measurement of the positions of celestial obj ...

satellite, gives a parallax of 116.89

mas Mas, Más or MAS may refer to: Film and TV * Más y Menos, fictional superhero characters, from the Teen Titans animated television series * Más (Breaking Bad), "Más" (''Breaking Bad''), a season three episode of ''Breaking Bad'' Songs * Más ( ...

, which corresponds to a physical separation of 27.9

light year A light-year, alternatively spelled light year, is a large unit of length used to express astronomical distances and is equivalent to about 9.46 trillion kilometers (), or 5.88 trillion miles ().One trillion here is taken to be 1012 ...

s from the Sun. This star is similar in physical properties to the Sun, with around 95% of the

Sun's mass The solar mass () is a standard unit of mass in astronomy, equal to approximately . It is often used to indicate the masses of other stars, as well as stellar clusters, nebulae, galaxies and black holes. It is approximately equal to the mass of ...

, 98% of the

radius In classical geometry, a radius ( : radii) of a circle or sphere is any of the line segments from its center to its perimeter, and in more modern usage, it is also their length. The name comes from the latin ''radius'', meaning ray but also the ...

, and 85% of the

Luminosity Luminosity is an absolute measure of radiated electromagnetic power (light), the radiant power emitted by a light-emitting object over time. In astronomy, luminosity is the total amount of electromagnetic energy emitted per unit of time by a st ...

. The abundance of elements is also similar to the Sun, with the star having an estimated 95% of the Sun's proportion of elements other than hydrogen and helium. It is older than the Sun at around 6.1–6.6 billion years of age, and is spinning with a leisurely

projected rotational velocity Stellar rotation is the angular motion of a star about its axis. The rate of rotation can be measured from the spectrum of the star, or by timing the movements of active features on the surface. The rotation of a star produces an equatorial bulge ...

of 4 km/s at the equator. On average, there is only a low level of activity in the stellar

chromosphere A chromosphere ("sphere of color") is the second layer of a star's atmosphere, located above the photosphere and below the solar transition region and corona. The term usually refers to the Sun's chromosphere, but not exclusively. In the Su ...

and it is a candidate for being in a Maunder minimum state. But the star was suspected as variable in 1988, and a burst of activity was observed between

Julian day The Julian day is the continuous count of days since the beginning of the Julian period, and is used primarily by astronomers, and in software for easily calculating elapsed days between two events (e.g. food production date and sell by date). ...

s 44800 (29 November 2008) and 55220 (23 January 2010). The space velocity components of this star are U = –37.9, V = –35.3 and W = –24.7 km/s. 61 Vir is orbiting through the

Milky Way The Milky Way is the galaxy that includes our Solar System, with the name describing the galaxy's appearance from Earth: a hazy band of light seen in the night sky formed from stars that cannot be individually distinguished by the naked eye ...

galaxy at a distance of 6.9 kpc from the core, with an

eccentricity Eccentricity or eccentric may refer to: * Eccentricity (behavior), odd behavior on the part of a person, as opposed to being "normal" Mathematics, science and technology Mathematics * Off-center, in geometry * Eccentricity (graph theory) of a v ...

of 0.15. It is believed to be a member of the disk population.

Planetary system

The ecliptic of the 61 Virginis system, as inferred from its dust disc, is inclined to the Solar system at 77°. The star itself is probably inclined at 72°. In 1988, a study surmised that 61 Virginis was a "possible variable", but no companions were then found. A subsequent study, over eleven years, also failed to find any companion up to the mass of Jupiter and out to 3 AU. On 14 December 2009, scientists announced the discovery of three

planets A planet is a large, rounded astronomical body that is neither a star nor its remnant. The best available theory of planet formation is the nebular hypothesis, which posits that an interstellar cloud collapses out of a nebula to create a young ...

with masses between 5 and 25 times that of Earth orbiting 61 Virginis. The three planets all orbit very near the star; when compared to the orbits of the planets in the Solar System, all three would orbit inside that of

Venus Venus is the second planet from the Sun. It is sometimes called Earth's "sister" or "twin" planet as it is almost as large and has a similar composition. As an interior planet to Earth, Venus (like Mercury) appears in Earth's sky never fa ...

. The outermost of these three, d, has not yet been confirmed in the HARPS data. A survey with 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 ...

revealed an excess of infrared radiation at a wavelength of 160 μm. This indicated the presence of a

debris disk A debris disk (American English), or debris disc (Commonwealth English), is a circumstellar disk of dust and debris in orbit around a star. Sometimes these disks contain prominent rings, as seen in the image of Fomalhaut on the right. Debris dis ...

in orbit around the star. This disk was resolved at 70 μm. It was then thought to correspond to an inner radius of 96 AU from the star and outer radius at 195 AU; it is now constrained 30 to over 100 AU. The total mass of the disk is the mass of the Earth. On 27 November 2012, the European Space Agency declared that the debris disc (like that of the

Gliese 581 planetary system Gliese 581 () is a red dwarf star of spectral type M3V at the center of the Gliese 581 planetary system, about 20 light years away from Earth in the Libra constellation. Its estimated mass is about a third of that of the Sun, and it is t ...

) has "at least 10 times" as many comets as does the Solar system. As of 2012, "planets more massive than Saturn orbiting within 6 AU" were ruled out. The ESA has further ruled out Saturn-mass planets beyond that. Additional data is needed to confirm the possibility of more sub-Saturn planets between 0.5 (really, 0.3) and 30 AU from the star. An Earth-mass planet in the star's habitable zone (which would still be too small to detect with current technology) remains possible.

61 Virginis d

61 Virginis d (abbreviated 61 Vir d, also designated as HD 115617 is a proposed exoplanet orbiting the 5th apparent-magnitude G-type main-sequence star 61 Virginis in the constellation Virgo. 61 Virginis d would have a minimum mass of 22.9 times that of Earth and orbits nearly one-half the distance to the star as Earth orbits the Sun with an eccentricity of 0.35. This planet would most likely be a gas giant like Uranus and Neptune. This planet was induced on 14 December 2009 from using a precise radial velocity method taken at Keck and Anglo-Australian Observatories. 3] A 2021 study found 61 Virginis d to be a false positive. File:61VirginisSystem.svg, 61 Virginis System

View from 61 Virginis

The

is barely visible from the system as a small star close to the much brighter

Sirius Sirius is the list of brightest stars, brightest star in the night sky. Its name is derived from the Ancient Greek language, Greek word , or , meaning 'glowing' or 'scorching'. The star is designated α Canis Majoris, Latinisation ...

Arcturus , - bgcolor="#FFFAFA" , Note (category: variability): , , H and K emission vary. Arcturus is the brightest star in the northern constellation of Boötes. With an apparent visual magnitude of −0.05, it is the third-brightest of th ...

(magnitude −1.01) is the brightest star of the night sky.

References

External links