61 Cygni
Overview
 
61 Cygni,Not to be confused with 16 Cygni
16 Cygni
16 Cygni or 16 Cyg is a triple star system approximately 70 light-years away from Earth in the constellation of Cygnus. It consists of two Sun-like yellow dwarf stars, 16 Cygni A and 16 Cygni B, together with a red dwarf, 16 Cygni C...

, a more distant system containing two G-type
Stellar classification
In astronomy, stellar classification is a classification of stars based on their spectral characteristics. The spectral class of a star is a designated class of a star describing the ionization of its chromosphere, what atomic excitations are most prominent in the light, giving an objective measure...

 stars harboring the gas giant
Gas giant
A gas giant is a large planet that is not primarily composed of rock or other solid matter. There are four gas giants in the Solar System: Jupiter, Saturn, Uranus, and Neptune...

 planet 16 Cygni Bb
16 Cygni Bb
16 Cygni Bb or 16 Cyg Bb is an extrasolar planet approximately 70 light-years away in the constellation of Cygnus. The planet was discovered orbiting the sun-like star 16 Cygni B, one of two solar-mass components of the triple star system 16 Cygni...

.
sometimes called Bessel's Star or Piazzi's Flying Star, is a binary star
Binary star
A binary star is a star system consisting of two stars orbiting around their common center of mass. The brighter star is called the primary and the other is its companion star, comes, or secondary...

 system in the constellation
Constellation
In modern astronomy, a constellation is an internationally defined area of the celestial sphere. These areas are grouped around asterisms, patterns formed by prominent stars within apparent proximity to one another on Earth's night sky....

 Cygnus
Cygnus (constellation)
Cygnus is a northern constellation lying on the plane of the Milky Way. Its name is the Latinized Hellenic word for swan. One of the most recognizable constellations of the northern summer and autumn, it features a prominent asterism known as the Northern Cross...

. It consists of a pair of K-type
Stellar classification
In astronomy, stellar classification is a classification of stars based on their spectral characteristics. The spectral class of a star is a designated class of a star describing the ionization of its chromosphere, what atomic excitations are most prominent in the light, giving an objective measure...

 dwarf star
Dwarf star
The term dwarf star refers to a variety of distinct classes of stars.* Dwarf star alone generally refers to any main sequence star, a star of luminosity class V.** Red dwarfs are low-mass main sequence stars....

s that orbit each other in a period of about 659 years, forming a visual binary. At fifth and sixth apparent magnitude
Apparent magnitude
The apparent magnitude of a celestial body is a measure of its brightness as seen by an observer on Earth, adjusted to the value it would have in the absence of the atmosphere...

s, they are among the least conspicuous stars visible in the night sky to an observer without an optical instrument
Optical instrument
An optical instrument either processes light waves to enhance an image for viewing, or analyzes light waves to determine one of a number of characteristic properties.-Image enhancement:...

.

61 Cygni first attracted the attention of astronomers because of its large proper motion
Proper motion
The proper motion of a star is its angular change in position over time as seen from the center of mass of the solar system. It is measured in seconds of arc per year, arcsec/yr, where 3600 arcseconds equal one degree. This contrasts with radial velocity, which is the time rate of change in...

.
Encyclopedia
61 Cygni,Not to be confused with 16 Cygni
16 Cygni
16 Cygni or 16 Cyg is a triple star system approximately 70 light-years away from Earth in the constellation of Cygnus. It consists of two Sun-like yellow dwarf stars, 16 Cygni A and 16 Cygni B, together with a red dwarf, 16 Cygni C...

, a more distant system containing two G-type
Stellar classification
In astronomy, stellar classification is a classification of stars based on their spectral characteristics. The spectral class of a star is a designated class of a star describing the ionization of its chromosphere, what atomic excitations are most prominent in the light, giving an objective measure...

 stars harboring the gas giant
Gas giant
A gas giant is a large planet that is not primarily composed of rock or other solid matter. There are four gas giants in the Solar System: Jupiter, Saturn, Uranus, and Neptune...

 planet 16 Cygni Bb
16 Cygni Bb
16 Cygni Bb or 16 Cyg Bb is an extrasolar planet approximately 70 light-years away in the constellation of Cygnus. The planet was discovered orbiting the sun-like star 16 Cygni B, one of two solar-mass components of the triple star system 16 Cygni...

.
sometimes called Bessel's Star or Piazzi's Flying Star, is a binary star
Binary star
A binary star is a star system consisting of two stars orbiting around their common center of mass. The brighter star is called the primary and the other is its companion star, comes, or secondary...

 system in the constellation
Constellation
In modern astronomy, a constellation is an internationally defined area of the celestial sphere. These areas are grouped around asterisms, patterns formed by prominent stars within apparent proximity to one another on Earth's night sky....

 Cygnus
Cygnus (constellation)
Cygnus is a northern constellation lying on the plane of the Milky Way. Its name is the Latinized Hellenic word for swan. One of the most recognizable constellations of the northern summer and autumn, it features a prominent asterism known as the Northern Cross...

. It consists of a pair of K-type
Stellar classification
In astronomy, stellar classification is a classification of stars based on their spectral characteristics. The spectral class of a star is a designated class of a star describing the ionization of its chromosphere, what atomic excitations are most prominent in the light, giving an objective measure...

 dwarf star
Dwarf star
The term dwarf star refers to a variety of distinct classes of stars.* Dwarf star alone generally refers to any main sequence star, a star of luminosity class V.** Red dwarfs are low-mass main sequence stars....

s that orbit each other in a period of about 659 years, forming a visual binary. At fifth and sixth apparent magnitude
Apparent magnitude
The apparent magnitude of a celestial body is a measure of its brightness as seen by an observer on Earth, adjusted to the value it would have in the absence of the atmosphere...

s, they are among the least conspicuous stars visible in the night sky to an observer without an optical instrument
Optical instrument
An optical instrument either processes light waves to enhance an image for viewing, or analyzes light waves to determine one of a number of characteristic properties.-Image enhancement:...

.

61 Cygni first attracted the attention of astronomers because of its large proper motion
Proper motion
The proper motion of a star is its angular change in position over time as seen from the center of mass of the solar system. It is measured in seconds of arc per year, arcsec/yr, where 3600 arcseconds equal one degree. This contrasts with radial velocity, which is the time rate of change in...

. In 1838, Friedrich Wilhelm Bessel measured its distance from Earth
Earth
Earth is the third planet from the Sun, and the densest and fifth-largest of the eight planets in the Solar System. It is also the largest of the Solar System's four terrestrial planets...

 at about 10.4 light years
Light Years
Light Years is the seventh studio album by Australian recording artist Kylie Minogue. It was released on 25 September 2000 by Parlophone and Mushroom Records. The album's style was indicative of her return to "mainstream pop dance tunes"....

, very close to the actual value of about 11.4 light years; this was the first distance estimate for any star other than the Sun
Sun
The Sun is the star at the center of the Solar System. It is almost perfectly spherical and consists of hot plasma interwoven with magnetic fields...

, and first star to have its stellar parallax
Stellar parallax
Stellar parallax is the effect of parallax on distant stars in astronomy. It is parallax on an interstellar scale, and it can be used to determine the distance of Earth to another star directly with accurate astrometry...

 measured. Over the course of the twentieth century, several different astronomers reported detections of a massive planet
Planet
A planet is a celestial body orbiting a star or stellar remnant that is massive enough to be rounded by its own gravity, is not massive enough to cause thermonuclear fusion, and has cleared its neighbouring region of planetesimals.The term planet is ancient, with ties to history, science,...

 orbiting one of the two stars, but recent high-precision radial velocity
Radial velocity
Radial velocity is the velocity of an object in the direction of the line of sight . In astronomy, radial velocity most commonly refers to the spectroscopic radial velocity...

 observations have shown that all such claims were erroneous. To date, no planets have been confirmed in this system and all of the past claims are now considered spurious.

Observation history

The large proper motion
Proper motion
The proper motion of a star is its angular change in position over time as seen from the center of mass of the solar system. It is measured in seconds of arc per year, arcsec/yr, where 3600 arcseconds equal one degree. This contrasts with radial velocity, which is the time rate of change in...

 of 61 Cygni was first demonstrated by Giuseppe Piazzi
Giuseppe Piazzi
Giuseppe Piazzi was an Italian Catholic priest of the Theatine order, mathematician, and astronomer. He was born in Ponte in Valtellina, and died in Naples. He established an observatory at Palermo, now the Osservatorio Astronomico di Palermo – Giuseppe S...

 in 1804, who christened it the "Flying Star". Piazzi's result, however, received little attention at the time due to the relatively short time span of his observations—a mere 10 years. It would take a publication by Friedrich Wilhelm Bessel in 1812 to bring this star to the widespread attention of astronomers.

Friedrich Georg Wilhelm von Struve
Friedrich Georg Wilhelm von Struve
Friedrich Georg Wilhelm von Struve was a Danish-Baltic German astronomer from a famous dynasty.-Life:...

 first argued for its status as a binary in 1830. For many years thereafter, however, some uncertainty remained as to whether this pair was a mere juxtaposition of stars or a gravitationally bound system
Star system
A star system or stellar system is a small number of stars which orbit each other, bound by gravitational attraction. A large number of stars bound by gravitation is generally called a star cluster or galaxy, although, broadly speaking, they are also star systems.-Binary star systems:A stellar...

.

The system's large proper motion, the largest known for any star at the time, made 61 Cygni a candidate for the determination of its distance by the method of parallax
Parallax
Parallax is a displacement or difference in the apparent position of an object viewed along two different lines of sight, and is measured by the angle or semi-angle of inclination between those two lines. The term is derived from the Greek παράλλαξις , meaning "alteration"...

 when the quality of astronomical observations first made this possible. The system therefore has the distinction of being the first star (excluding the Sun) to have its distance from Earth measured. This was accomplished in 1838 by Bessel
Bessel
Bessel may refer to:* Bessel beam* Bessel ellipsoid* Bessel function in mathematics* Bessel's inequality in mathematics* Bessel filter, a linear filter often used in audio crossover systems* Bessel , a small lunar crater...

, who arrived at a parallax of 313.6 mas
Minute of arc
A minute of arc, arcminute, or minute of angle , is a unit of angular measurement equal to one sixtieth of one degree. In turn, a second of arc or arcsecond is one sixtieth of one minute of arc....

, close to the currently accepted value of 287.18 mas (yielding 11.36 light years).

Only a few years later, however, Groombridge 1830
Groombridge 1830
Groombridge 1830 is a star in the constellation Ursa Major.-Description:It is a yellowish class G8 subdwarf catalogued by Stephen Groombridge with the Groombridge Transit Circle between 1806 and the 1830s and published posthumously in his star catalog, Catalogue of Circumpolar Stars...

 was discovered to have a larger proper motion. 61 Cygni retains the distinction of having the largest proper motion of any star visible to the unaided eye (although Groombridge 1830 at magnitude 6.4 can be seen with the naked eye under exceptionally dark skies). 61 Cygni has the seventh highest proper motion of all stellar systems listed in the Hipparcos Catalogue.

By 1911, Bessel's parallax of 0.3136 had only slightly improved to 0.310, and observations at Yerkes Observatory
Yerkes Observatory
Yerkes Observatory is an astronomical observatory operated by the University of Chicago in Williams Bay, Wisconsin. The observatory, which calls itself "the birthplace of modern astrophysics," was founded in 1897 by George Ellery Hale and financed by Charles T. Yerkes...

 had measured its radial velocity as 62 km/s which together with its proper motion—transverse to our line of sight—of around 79 km/s yielded a space velocity of about 100 km/s towards a point about 12 degrees west of Orion
Orion (constellation)
Orion, often referred to as The Hunter, is a prominent constellation located on the celestial equator and visible throughout the world. It is one of the most conspicuous, and most recognizable constellations in the night sky...

's belt.The space velocity calculated from 1911 data: parallax 310 mas yields 10.5 light years; total proper motion= 5.205 arcsec/year (average by mass) or 79.4 km/s; and radial velocity = -62 km/s.This yields a 1911 space velocity of  km/s. Compare with more accurate 1953, 1997 data: parallax 287.18 yields 11.36 ly and so an increased proper motion velocity of 87 km/s; radial velocity -64 km/s yields a net space velocity of  km/s.

In 1911, Benjamin Boss
Benjamin Boss
Benjamin Boss was anAmerican astronomer.He was born to Lewis Boss and Helen M. Boss. After attending The Albany Academy, he graduated from Harvard University in 1901 and worked at Dudley Observatory until 1905. Following a year at the U. S. Naval Observatory in Washington, D.C., he became director...

 published data indicating that the 61 Cygni system was a member of a comoving group of stars. This group was later expanded to include 26 potential members. Possible members include Beta Columbae
Beta Columbae
Beta Columbae is a K-type giant star and is the second brightest star in the constellation of Columba. It has the traditional name Wezn , from the Arabic وزن "weight".In Chinese, , meaning Son, refers to an asterism consisting of β Columbae and λ Columbae...

, Pi Mensae
Pi Mensae
Pi Mensae is a yellow subgiant star in the constellation of Mensa. This star has a high proper motion. The apparent magnitude is 5.67, which can be visible to the naked eye in exceptionally dark, clear skies. It is nearly 60 ly away. The star dwarfs the Sun in terms of mass, size, luminosity,...

, 14 Tauri and 68 Virginis. The typical space velocities of this group of stars is 105–114 km/s relative to the Sun.

Because of their wide angular separation (and correspondingly slow orbital motion), it was initially unclear whether the two stars in the 61 Cygni system were physically connected. The respective parallax measurements of 0.360″ and 0.288″ gave a separation of more than two light years. However, by 1917 refined measured parallax differences demonstrated that the separation was significantly less. The binary nature of this system was clear by 1934, and orbital elements
Orbital elements
Orbital elements are the parameters required to uniquely identify a specific orbit. In celestial mechanics these elements are generally considered in classical two-body systems, where a Kepler orbit is used...

 were published.

An observer using 7×50 binoculars
Binoculars
Binoculars, field glasses or binocular telescopes are a pair of identical or mirror-symmetrical telescopes mounted side-by-side and aligned to point accurately in the same direction, allowing the viewer to use both eyes when viewing distant objects...

 can find 61 Cygni two binocular fields south-east of the bright star Deneb
Deneb
Deneb is the brightest star in the constellation Cygnus and one of the vertices of the Summer Triangle. It is the 19th brightest star in the night sky, with an apparent magnitude of 1.25. A blue-white supergiant, Deneb is also one of the most luminous nearby stars...

. The angular separation of the two stars is slightly greater than the angular size of Saturn
Saturn
Saturn is the sixth planet from the Sun and the second largest planet in the Solar System, after Jupiter. Saturn is named after the Roman god Saturn, equated to the Greek Cronus , the Babylonian Ninurta and the Hindu Shani. Saturn's astronomical symbol represents the Roman god's sickle.Saturn,...

 (16–20″). So, under ideal viewing conditions, the binary system can be resolved by a telescope with a 6 mm aperture.Per the Rayleigh criterion
Angular resolution
Angular resolution, or spatial resolution, describes the ability of any image-forming device such as an optical or radio telescope, a microscope, a camera, or an eye, to distinguish small details of an object...

:
 mm.
This is
well within the capability of a typical pair of binoculars.

Properties

Although it appears to be a single star to the naked eye, 61 Cygni is in fact a widely separated binary system
Binary star
A binary star is a star system consisting of two stars orbiting around their common center of mass. The brighter star is called the primary and the other is its companion star, comes, or secondary...

, composed of two K class (orange)
Stellar classification
In astronomy, stellar classification is a classification of stars based on their spectral characteristics. The spectral class of a star is a designated class of a star describing the ionization of its chromosphere, what atomic excitations are most prominent in the light, giving an objective measure...

 main sequence
Main sequence
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 Hertzsprung and Henry Norris Russell...

 stars, 61 Cygni A and 61 Cygni B. The brighter star 61 Cygni A is of apparent magnitude
Apparent magnitude
The apparent magnitude of a celestial body is a measure of its brightness as seen by an observer on Earth, adjusted to the value it would have in the absence of the atmosphere...

 5.2, the fainter 61 Cygni B is 6.1. Both appear to be old-disk stars, with an estimated age that is older than the Sun. The system has a net space velocity of 108 km/s relative to the Sun, which results in the high proper motion across the sky. At a distance of just over 11 light years, it is the 15th nearest known star system to the Earth (not including the Sun). 61 Cygni A is the fourth nearest star that is visible to the naked eye for mid-latitude northern observers, after Sirius
Sirius
Sirius is the brightest star in the night sky. With a visual apparent magnitude of −1.46, it is almost twice as bright as Canopus, the next brightest star. The name "Sirius" is derived from the Ancient Greek: Seirios . The star has the Bayer designation Alpha Canis Majoris...

, Epsilon Eridani
Epsilon Eridani
Epsilon Eridani is a star in the southern constellation Eridanus, along a declination 9.46° south of the celestial equator. This allows the star to be viewed from most of the Earth's surface. At a distance of 10.5 light years , it has an apparent magnitude of 3.73...

, and Procyon A. This system will make its closest approach at about 20,000 CE
Common Era
Common Era ,abbreviated as CE, is an alternative designation for the calendar era originally introduced by Dionysius Exiguus in the 6th century, traditionally identified with Anno Domini .Dates before the year 1 CE are indicated by the usage of BCE, short for Before the Common Era Common Era...

, when the separation from the Sun will be about 9 light years.

The two orbit their common barycenter
Barycentric coordinates (astronomy)
In astronomy, barycentric coordinates are non-rotating coordinates with origin at the center of mass of two or more bodies.The barycenter is the point between two objects where they balance each other. For example, it is the center of mass where two or more celestial bodies orbit each other...

 in a period of 659 years, with a mean separation of about 84 A.U.—84 times the separation between the Earth and the Sun. The relatively large orbital eccentricity
Orbital eccentricity
The orbital eccentricity of an astronomical body is the amount by which its orbit deviates from a perfect circle, where 0 is perfectly circular, and 1.0 is a parabola, and no longer a closed orbit...

 of 0.48 means that the two stars are separated by about 44 A.U. at periapsis and 124 A.U. at apoapsis.At periapsis:  A.U.
At apoapsis:  A.U.
The leisurely orbit of the pair has made it difficult to pin down their respective masses, and the accuracy of these values remain somewhat controversial. In the future this issue may be resolved through the use of asteroseismology
Asteroseismology
Asteroseismology also known as stellar seismology is the science that studies the internal structure of pulsating stars by the interpretation of their frequency spectra. Different oscillation modes penetrate to different depths inside the star...

.

Component A has about 11% more mass than component B. It has an activity cycle
Stellar magnetic field
A stellar magnetic field is a magnetic field generated by the motion of conductive plasma inside a star. This motion is created through convection, which is a form of energy transport involving the physical movement of material. A localized magnetic field exerts a force on the plasma, effectively...

 that is much more pronounced than the solar sunspot
Sunspot
Sunspots are temporary phenomena on the photosphere of the Sun that appear visibly as dark spots compared to surrounding regions. They are caused by intense magnetic activity, which inhibits convection by an effect comparable to the eddy current brake, forming areas of reduced surface temperature....

 cycle. This is a complex activity cycle that varies with a period of about 7.5±1.7 years. (An earlier estimate gave a period of 7.3 years.) The combination of starspot activity combined with rotation and chromospheric activity is characteristic of a BY Draconis variable
BY Draconis variable
BY Draconis variables are main sequence variable stars of late spectral types, usually K or M. The name comes from the archetype for this category of variable star system, BY Draconis. They exhibit variations in their luminosity due to rotation of the star coupled with star spots, and other...

. Because of differential rotation, this star's surface rotation period varies by latitude from 27 to 45 days, with an average period of 35 days.
The outflow of the stellar wind from component A produces a bubble within the local interstellar cloud. Along the direction of the star's motion within the Milky Way, this extends out to a distance of only 30 AU, or roughly the orbital distance of Neptune
Neptune
Neptune is the eighth and farthest planet from the Sun in the Solar System. Named for the Roman god of the sea, it is the fourth-largest planet by diameter and the third largest by mass. Neptune is 17 times the mass of Earth and is slightly more massive than its near-twin Uranus, which is 15 times...

 from the Sun. This is lower than the separation between the two components of 61 Cygni, and so the two most likely do not share a common atmosphere. The compactness of the astrosphere is likely due to the low mass outflow and the relatively high velocity through the local medium.

Component B displays a more chaotic pattern of variability than A, with significant short-term flares. There is an 11.7-year periodicity to the overall activity cycle of B. Both stars exhibit stellar flare activity, but the chromosphere
Chromosphere
The chromosphere is a thin layer of the Sun's atmosphere just above the photosphere, roughly 2,000 kilometers deep....

 of component B is 25% more active than for component A. As a result of differential rotation, the period of rotation varies by latitude from 32 to 47 days, with an average period of 38 days.

There is some disagreement over the evolutionary age of this system. Kinematic
Stellar kinematics
Stellar kinematics is the study of the movement of stars without needing to understand how they acquired their motion. This differs from stellar dynamics, which takes into account gravitational effects...

 data gives an age estimate of about 10 Gyr. Gyrochronology
Stellar rotation
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....

, or the age determination of a star based on its rotation and color, results in an average age of . The ages based on chromospheric activity
Stellar magnetic field
A stellar magnetic field is a magnetic field generated by the motion of conductive plasma inside a star. This motion is created through convection, which is a form of energy transport involving the physical movement of material. A localized magnetic field exerts a force on the plasma, effectively...

 for A and B are 2.36 Gyr and 3.75 Gyr, respectively. Finally the age estimates using the isochrone method, which involve fitting the stars to evolutionary models, yield upper limits of 0.44 Gyr and 0.68 Gyr. However, a 2008 evolutionary model using the CESAM2k code from the Côte d'Azur Observatory
Côte d'Azur Observatory
The Observatoire de la Côte d'Azur originated in 1988 with the merger of two observatories:# Observatoire de Nice# The CERGA - External links :*...

 gives an age estimate of for the pair.

Claims of a planetary system

On several occasions, it has been claimed that 61 Cygni has unseen low-mass companions, planets or a brown dwarf
Brown dwarf
Brown dwarfs are sub-stellar objects which are too low in mass to sustain hydrogen-1 fusion reactions in their cores, which is characteristic of stars on the main sequence. Brown dwarfs have fully convective surfaces and interiors, with no chemical differentiation by depth...

. Kaj Strand
Kaj Aage Gunnar Strand
Kaj Aage Gunnar Strand was a Danish astronomer who worked in Denmark and the United States He was Scientific Director of the U.S. Naval Observatory from 1963 to 1977. He specialized in astrometry, especially work on double stars and stellar distances. -Life:Kaj Strand was born February 27, 1907 in...

 of the Sproul Observatory
Sproul Observatory
Sproul Observatory is an astronomical observatory owned and operated by Swarthmore College. It is located in Swarthmore, Pennsylvania, United States, and is named after William Cameron Sproul, the 27th Governor of Pennsylvania, who graduated from Swarthmore in 1891.-Tours:An open house is offered...

, under the direction of Peter van de Kamp
Peter van de Kamp
Piet van de Kamp , known as Peter van de Kamp in the United States, was a Dutch astronomer who lived most of his life in the United States. He was professor of astronomy at Swarthmore College and director of the college's Sproul Observatory from 1937 until 1972...

, made the first such claim in 1942 using observations to detect tiny but systematic variations in the orbital motions of 61 Cygni A and B. These perturbations suggested that a third body was orbiting 61 Cygni A. In 1957, he narrowed his uncertainties, claiming that the object had a mass eight times the mass of Jupiter
Jupiter
Jupiter is the fifth planet from the Sun and the largest planet within the Solar System. It is a gas giant with mass one-thousandth that of the Sun but is two and a half times the mass of all the other planets in our Solar System combined. Jupiter is classified as a gas giant along with Saturn,...

, a calculated orbital period of 4.8 years, and a semi-major axis of 2.4 A.U. In 1977, Soviet astronomers at the Pulkovo Observatory
Pulkovo Observatory
The Pulkovo Astronomical Observatory астрономи́ческая обсервато́рия Росси́йской акаде́мии нау́к), the principal astronomical observatory of the Russian Academy of Sciences, located 19 km south of Saint Petersburg on Pulkovo Heights...

 near Saint Petersburg
Saint Petersburg
Saint Petersburg is a city and a federal subject of Russia located on the Neva River at the head of the Gulf of Finland on the Baltic Sea...

 suggested that the system included three planets: two giant planets with six and twelve Jupiter masses around 61 Cyg A, and one giant planet with seven Jupiter masses around 61 Cygni B. In 1978, Wulff Dieter Heintz
Wulff Dieter Heintz
Wulff-Dieter Heintz was a German astronomer who worked the latter part of his career in the United States. He was Professor Emeritus of Astronomy at Swarthmore College and former director of the Sproul Observatory...

 of the Sproul Observatory
Sproul Observatory
Sproul Observatory is an astronomical observatory owned and operated by Swarthmore College. It is located in Swarthmore, Pennsylvania, United States, and is named after William Cameron Sproul, the 27th Governor of Pennsylvania, who graduated from Swarthmore in 1891.-Tours:An open house is offered...

 proved that these claims, as well as the claims for unseen companions around many other stars, were spurious, having failed to detect any evidence of such motion down to six percent of the Sun's mass—equivalent to about 60 times the mass of Jupiter
Jupiter
Jupiter is the fifth planet from the Sun and the largest planet within the Solar System. It is a gas giant with mass one-thousandth that of the Sun but is two and a half times the mass of all the other planets in our Solar System combined. Jupiter is classified as a gas giant along with Saturn,...

.

Refining planetary boundaries

Since no certain planetary object has been detected around either star so far, McDonald Observatory
McDonald Observatory
The McDonald Observatory is an astronomical observatory located near the unincorporated community of Fort Davis in Jeff Davis County, Texas, United States. The facility is located on Mount Fowlkes and Mount Locke in the Davis Mountains of West Texas...

 team has set limits to the presence of one or more planets around 61 Cygni A and 61 Cygni B with masses between 0.07 and 2.4 Jupiter masses and average separations spanning between 0.05 and 5.2 A.U.

Because of the proximity of this system to the Sun, it is a frequent target of interest for astronomers. Both stars were selected by NASA
NASA
The National Aeronautics and Space Administration is the agency of the United States government that is responsible for the nation's civilian space program and for aeronautics and aerospace research...

 as "Tier 1" targets for the proposed optical Space Interferometry Mission
Space Interferometry Mission
The Space Interferometry Mission, or SIM, also known as SIM Lite , was a planned space telescope developed by the U.S. National Aeronautics and Space Administration , in conjunction with contractor Northrop Grumman...

. This mission is potentially capable of detecting planets with as little as 3 times the mass of the Earth at an orbital distance of 2 A.U. from the star. Measurements of this system have detected an excess of far infrared
Infrared
Infrared light is electromagnetic radiation with a wavelength longer than that of visible light, measured from the nominal edge of visible red light at 0.74 micrometres , and extending conventionally to 300 µm...

 radiation, beyond what is emitted by the stars. Such an excess is sometimes associated with a disk of dust
Debris disk
A debris disk 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 disks have been found around both evolved and young stars, as well as at least one debris disk in orbit around a...

, but in this case it lies sufficiently close to one or both of the stars that it has not yet been resolved with a telescope.

See also

  • List of nearest stars
  • 61 Cygni in fiction — Stars and planetary systems in fiction
  • Barnard's Star
    Barnard's star
    Barnard's Star, also known occasionally as Barnard's "Runaway" Star, is a very low-mass red dwarf star approximately six light-years away from Earth in the constellation of Ophiuchus . In 1916, the American astronomer E.E...


External links

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