61 Virginis (abbreviated 61 Vir) is 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, main-sequence star (luminosity class V) of stellar classification, spectral type G. Such a star has about 0.9 to ...

(G7V) slightly less massive than the

Sun The Sun is the star at the centre of the Solar System. It is a massive, nearly perfect sphere of hot plasma, heated to incandescence by nuclear fusion reactions in its core, radiating the energy from its surface mainly as visible light a ...

(which has a hotter G2V spectral type), located 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 first constellati ...

Virgo Virgo may refer to: Arts and entertainment * Virgo (film), a 1970 Egyptian film * Virgo (character), several Marvel Comics characters * Virgo Asmita, a character in the manga ''Saint Seiya: The Lost Canvas'' * ''Virgo'' (album), by Virgo Four, ...

. The composition of this star is nearly identical to the Sun.

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 gratin ...

of G7 V. It is faint but visible to the naked eye in the

zodiac The zodiac is a belt-shaped region of the sky that extends approximately 8° north and south celestial latitude of the ecliptic – the apparent path of the Sun across the celestial sphere over the course of the year. Within this zodiac ...

, close to

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 ...

, the brightest star in the constellation. 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 ...

, 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 changes in the apparent places of stars or other celestial objects as they move relative to the center of mass of the Solar System. It is measured relative to the distant stars or a stable referenc ...

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

Gaia In Greek mythology, Gaia (; , a poetic form of ('), meaning 'land' or 'earth'),, , . also spelled Gaea (), is the personification of Earth. Gaia is the ancestral mother—sometimes parthenogenic—of all life. She is the mother of Uranus (S ...

satellite, gives a parallax of 117.17 mas (0.117"), which corresponds to a distance of . This star is similar in physical properties to the Sun, with around 93% of the

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

, 99% of the

radius In classical geometry, a radius (: radii or radiuses) of a circle or sphere is any of the line segments from its Centre (geometry), center to its perimeter, and in more modern usage, it is also their length. The radius of a regular polygon is th ...

, and 82% of the

luminosity Luminosity is an absolute measure of radiated electromagnetic radiation, electromagnetic energy per unit time, and is synonymous with the radiant power emitted by a light-emitting object. In astronomy, luminosity is the total amount of electroma ...

. 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, around 6.1–6.6 billion years old, 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 bu ...

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", from the Ancient Greek words χρῶμα (''khrôma'') 'color' and σφαῖρα (''sphaîra'') 'sphere') is the second layer of a Stellar atmosphere, star's atmosphere, located above the photosphere and below t ...

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 a continuous count of days from the beginning of the Julian period; it 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). Th ...

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 or Milky Way Galaxy is the galaxy that includes the Solar System, with the name describing the #Appearance, galaxy's appearance from Earth: a hazy band of light seen in the night sky formed from stars in other arms of the galax ...

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-Centre (geometry), center, in geometry * Eccentricity (g ...

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

Planetary system

On 14 December 2009, scientists announced the discovery of three

exoplanet An exoplanet or extrasolar planet is a planet outside the Solar System. The first confirmed detection of an exoplanet was in 1992 around a pulsar, and the first detection around a main-sequence star was in 1995. A different planet, first det ...

s with

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

es between 5 and 25 times that of Earth orbiting 61 Virginis, 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 th ...

at the Keck and Anglo-Australian Observatories. 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 often called Earth's "twin" or "sister" planet for having almost the same size and mass, and the closest orbit to Earth's. While both are rocky planets, Venus has an atmosphere much thicker ...

. The two outer planets likely resemble Uranus and Neptune, while the innermost planet may be a

mini-Neptune A Mini-Neptune (sometimes known as a gas dwarf or transitional planet) is a planet less massive than Neptune but resembling Neptune in that it has a thick hydrogen-helium atmosphere, probably with deep layers of ice, rock or liquid oceans (made o ...

or a rocky super-Earth. The outermost of these three planets, 61 Virginis d (also designated HD 115617 d), was initially not detected in the

HARPS The High Accuracy Radial Velocity Planet Searcher (HARPS) is a high-precision Echelle grating, echelle planet-finding spectrograph installed in 2002 on the ESO 3.6 m Telescope, ESO's 3.6m telescope at La Silla Observatory in Chile. The First l ...

data as of 2012 until a reanalysis of the data was done in 2023. A 2021 study listed it as a false positive, but in 2023 two published studies further confirmed it based on an additional 10 years of radial velocity data, though with a smaller minimum mass. Assuming the planets are aligned with the disk around the star, 61 Virginis b, c and d should have masses of .

Debris disk

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°. 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, that was deactivated when operations ended on 30 January 2020. Spitzer was the third space telescope dedicate ...

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 ...

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 Gliese 581 () is a red dwarf star of spectral type M3V which hosts a planetary system, away from Earth in the constellation Libra. Its estimated mass is about a third of that of the Sun, and it is the 101st closest known star system to ...

planetary system) has "at least 10 times" as many comets as does the Solar System's

Kuiper belt The Kuiper belt ( ) is a circumstellar disc in the outer Solar System, extending from the orbit of Neptune at 30 astronomical units (AU) to approximately 50 AU from the Sun. It is similar to the asteroid belt, but is far larger—20 times ...

Limits on additional planets

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. As of 2012, "planets more massive than Saturn orbiting within 6 AU" were ruled out. The ESA has found no evidence for Saturn-mass planets beyond that. Additional data is needed to confirm the possibility of more sub-Saturn planets between 0.5 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. File:61VirginisSystem.svg, Diagram of the 61 Virginis system

View from 61 Virginis

The

is visible from the system as a magnitude 4.50 star close to the stars

Hamal Hamal, pronounced , is a star in the northern zodiacal constellation of Aries. It has the Bayer designation Alpha Arietis, which is Latinized from α Arietis and abbreviated Alpha Ari or α Ari. This star is visible to the naked eye wit ...

, Beta Arietis and

Alpha Centauri Alpha Centauri (, α Cen, or Alpha Cen) is a star system in the southern constellation of Centaurus (constellation), Centaurus. It consists of three stars: Rigil Kentaurus (), Toliman (), and Proxima Centauri (). Proxima Centauri ...

Arcturus , - bgcolor="#FFFAFA" , Note (category: variability): , , H and K emission vary. Arcturus is a red giant star in the Northern celestial hemisphere, northern constellation of Boötes, and the brightest star in the constellation. It ha ...

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

Notes

References

External links

*
61 Virginis
at SolStation
Systemic Blog article with comparative map of orbits of 61 Vir b, c and d
* Aladi
image
of 61 Virginis {{DEFAULTSORT:61 Virginis G-type main-sequence stars Virginis, 061 Maunder Minimum Planetary systems with three confirmed planets Circumstellar disks Virgo (constellation) BD-17 3813 Virginis, 061 0506 115617 064924

5019 5 (five) is a number, numeral and digit. It is the natural number, and cardinal number, following 4 and preceding 6, and is a prime number. Humans, and many other animals, have 5 digits on their limbs. Mathematics 5 is a Fermat pri ...