VB 10
Encyclopedia
VB 10, also referred to as Van Biesbroeck's star, is a very small and very dim M-type
red dwarf
star
located in the constellation
Aquila
. Although it is relatively close to the Earth, at about 19 light years, VB 10 is a very dim magnitude
17, making it very difficult to image even with a large telescope.
using the 82 in (2.1 m) Otto Struve reflector telescope
at the McDonald Observatory
. He found it while surveying the telescopic field of view of the high proper motion
red dwarf
star Wolf 1055, for companions. Wolf 1055 had been catalogued 25 years earlier by German
astronomer Max Wolf
using similar astrophotographic
techniques. It is designated as VB 10 in the 1961 publication of Van Biesbroeck's star catalog
. Later, other astronomers began referring to it as Van Biesbroeck's Star
in honor of its discoverer. Because it is so dim and so close to its much brighter primary star
, earlier astronomical surveys
missed it even though its large parallax
and large proper motion
should have made it stand out on photographic plates taken at different times.
of nearly 19, making it very difficult to see. Later researchers also noted that its mass, at .08 solar mass, is right at the lower limit needed to create internal pressures and temperatures high enough to initiate nuclear fusion
and actually be a star
rather than a brown dwarf
. At the time of its discovery it was the lowest-mass star known. The previous record holder for the lowest mass was the star Wolf 359 at 0.09 solar mass.
VB 10 is also notable by its very large proper motion
, moving more than one arc second a year through the sky as seen from the Earth.
and is identified in the General Catalogue of Variable Stars
as V1298 Aquilae. It is classified as a UV Ceti type variable star and is known to be subject to frequent flare events
. Its dynamics were studied from the Hubble Space Telescope
in the mid-1990s and although the star has a normally cool surface temperature of 2600 K
it was found to produce violent flares of up to 100,000 K.
of a bound binary star system. This star is identified as Gliese 752 B component of that system. The primary star is the much larger and brighter Wolf 1055 (Gliese (GJ) 752 A). The two stars are separated by about 74 arc seconds (~434 AU).
's Jet Propulsion Laboratory
, Pasadena, California
, announced that they had found evidence of a planet, which they designated as VB 10b, orbiting the star. The 200 in (5.1 m) Hale telescope
at the Palomar Observatory
was used to detect evidence of this planet using the astrometry method. The new planet was claimed to have a mass 6 times that of Jupiter
and an orbital period of 270 days. However, subsequent studies using Doppler spectroscopy
failed to detect the radial velocity variations that would be expected if such a planet was orbiting this small star. The claimants of VB 10b note that these Doppler measurements only rule out planets more massive than 3 times the mass of Jupiter, but this limit is only half the reported best-fit mass of the planet as originally claimed. The claims for this planet thus fall into a long history of claimed astrometric extrasolar planet
detections that were subsequently refuted.
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...
red dwarf
Red dwarf
According to the Hertzsprung-Russell diagram, a red dwarf star is a small and relatively cool star, of the main sequence, either late K or M spectral type....
star
Star
A star is a massive, luminous sphere of plasma held together by gravity. At the end of its lifetime, a star can also contain a proportion of degenerate matter. The nearest star to Earth is the Sun, which is the source of most of the energy on Earth...
located 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....
Aquila
Aquila (constellation)
Aquila is a stellar constellation. Its name is Latin for 'eagle' and it is commonly represented as such. In mythology, Aquila was owned by the Roman god Jupiter and performed many tasks for him....
. Although it is relatively close to the Earth, at about 19 light years, VB 10 is a very dim 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...
17, making it very difficult to image even with a large telescope.
History
VB 10 was discovered in 1944 by the astronomer George van BiesbroeckGeorge Van Biesbroeck
George A. Van Biesbroeck was a Belgian-American astronomer. He worked at observatories in Belgium, Germany and the United States. He specialized in the observation of double stars, asteroids and comets...
using the 82 in (2.1 m) Otto Struve reflector telescope
Otto Struve Telescope
The Otto Struve Telescope was the first major telescope to be built at McDonald Observatory. Located in the Davis Mountains in West Texas, the Otto Struve Telescope was designed by Warner & Swasey Company and constructed between 1933 and 1939 by the Paterson-Leitch Company. Its 2.1 meter mirror...
at the 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...
. He found it while surveying the telescopic field of view of the high 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...
red dwarf
Red dwarf
According to the Hertzsprung-Russell diagram, a red dwarf star is a small and relatively cool star, of the main sequence, either late K or M spectral type....
star Wolf 1055, for companions. Wolf 1055 had been catalogued 25 years earlier by German
Germans
The Germans are a Germanic ethnic group native to Central Europe. The English term Germans has referred to the German-speaking population of the Holy Roman Empire since the Late Middle Ages....
astronomer Max Wolf
Max Wolf
Maximilian Franz Joseph Cornelius Wolf was a German astronomer and a pioneer in the field of astrophotography...
using similar astrophotographic
Astrophotography
Astrophotography is a specialized type of photography that entails recording images of astronomical objects and large areas of the night sky. The first photographs of an astronomical object were taken in the 1840s, but it was not until the late 19th century that advances in technology allowed for...
techniques. It is designated as VB 10 in the 1961 publication of Van Biesbroeck's star catalog
Van Biesbroeck's star catalog
In 1961 the astronomer George Van Biesbroeck published a catalog of low luminosity stars discovered using the Otto Struve refractor telescope of the McDonald Observatory in Texas. This survey is similar to earlier dim star surveys that were done by Max Wolf and Frank Elmore Ross but using later...
. Later, other astronomers began referring to it as Van Biesbroeck's Star
Stars named after people
Over the past few centuries, a small number of stars have been named after individual people. It is common in astronomy for objects to be given names, in accordance with accepted astronomical naming conventions...
in honor of its discoverer. Because it is so dim and so close to its much brighter primary 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...
, earlier astronomical surveys
Astronomical surveys
An astronomical survey is a general map or image of a region of the sky which lacks a specific observational target. Alternatively, an astronomical survey may comprise a set of many images of objects which share a common type or feature...
missed it even though its large 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"...
and 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...
should have made it stand out on photographic plates taken at different times.
Characteristics
VB 10 has an extremely low luminosity with an absolute magnitudeAbsolute magnitude
Absolute magnitude is the measure of a celestial object's intrinsic brightness. it is also the apparent magnitude a star would have if it were 32.6 light years away from Earth...
of nearly 19, making it very difficult to see. Later researchers also noted that its mass, at .08 solar mass, is right at the lower limit needed to create internal pressures and temperatures high enough to initiate nuclear fusion
Nuclear fusion
Nuclear fusion is the process by which two or more atomic nuclei join together, or "fuse", to form a single heavier nucleus. This is usually accompanied by the release or absorption of large quantities of energy...
and actually be a star
Star
A star is a massive, luminous sphere of plasma held together by gravity. At the end of its lifetime, a star can also contain a proportion of degenerate matter. The nearest star to Earth is the Sun, which is the source of most of the energy on Earth...
rather than 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...
. At the time of its discovery it was the lowest-mass star known. The previous record holder for the lowest mass was the star Wolf 359 at 0.09 solar mass.
VB 10 is also notable by its very 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...
, moving more than one arc second a year through the sky as seen from the Earth.
Flare star
VB 10 is a variable starVariable star
A star is classified as variable if its apparent magnitude as seen from Earth changes over time, whether the changes are due to variations in the star's actual luminosity, or to variations in the amount of the star's light that is blocked from reaching Earth...
and is identified in the General Catalogue of Variable Stars
General Catalogue of Variable Stars
The General Catalogue of Variable Stars is a list of variable stars. Its first edition, containing 10,820 stars, was published in 1948 by the Academy of Sciences of the USSR and edited by B. V. Kukarkin and P. P. Parenago. Second and third editions were published in 1958 and 1968; the fourth...
as V1298 Aquilae. It is classified as a UV Ceti type variable star and is known to be subject to frequent flare events
Flare star
A flare star is a variable star that can undergo unpredictable dramatic increases in brightness for a few minutes. It is believed that the flares on flare stars are analogous to solar flares in that they are due to magnetic reconnection in the atmospheres of the stars. The brightness increase is...
. Its dynamics were studied from the Hubble Space Telescope
Hubble Space Telescope
The Hubble Space Telescope is a space telescope that was carried into orbit by a Space Shuttle in 1990 and remains in operation. A 2.4 meter aperture telescope in low Earth orbit, Hubble's four main instruments observe in the near ultraviolet, visible, and near infrared...
in the mid-1990s and although the star has a normally cool surface temperature of 2600 K
Kelvin
The kelvin is a unit of measurement for temperature. It is one of the seven base units in the International System of Units and is assigned the unit symbol K. The Kelvin scale is an absolute, thermodynamic temperature scale using as its null point absolute zero, the temperature at which all...
it was found to produce violent flares of up to 100,000 K.
Binary star
VB 10 is the secondary starBinary 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...
of a bound binary star system. This star is identified as Gliese 752 B component of that system. The primary star is the much larger and brighter Wolf 1055 (Gliese (GJ) 752 A). The two stars are separated by about 74 arc seconds (~434 AU).
Claims of a planetary system
In May 2009, astronomers from NASANASA
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...
's Jet Propulsion Laboratory
Jet Propulsion Laboratory
Jet Propulsion Laboratory is a federally funded research and development center and NASA field center located in the San Gabriel Valley area of Los Angeles County, California, United States. The facility is headquartered in the city of Pasadena on the border of La Cañada Flintridge and Pasadena...
, Pasadena, California
Pasadena, California
Pasadena is a city in Los Angeles County, California, United States. Although famous for hosting the annual Rose Bowl football game and Tournament of Roses Parade, Pasadena is the home to many scientific and cultural institutions, including the California Institute of Technology , the Jet...
, announced that they had found evidence of a planet, which they designated as VB 10b, orbiting the star. The 200 in (5.1 m) Hale telescope
Hale telescope
The Hale Telescope is a , 3.3 reflecting telescope at the Palomar Observatory in California, named after astronomer George Ellery Hale. With funding from the Rockefeller Foundation, he orchestrated the planning, design, and construction of the observatory, but did not live to see its commissioning...
at the Palomar Observatory
Palomar Observatory
Palomar Observatory is a privately owned observatory located in San Diego County, California, southeast of Pasadena's Mount Wilson Observatory, in the Palomar Mountain Range. At approximately elevation, it is owned and operated by the California Institute of Technology...
was used to detect evidence of this planet using the astrometry method. The new planet was claimed to have a mass 6 times that 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,...
and an orbital period of 270 days. However, subsequent studies using Doppler spectroscopy
Doppler spectroscopy
Doppler spectroscopy, also known as radial velocity measurement, is a spectroscopic method for finding extrasolar planets. It involves the observation of Doppler shifts in the spectrum of the star around which the planet orbits....
failed to detect the radial velocity variations that would be expected if such a planet was orbiting this small star. The claimants of VB 10b note that these Doppler measurements only rule out planets more massive than 3 times the mass of Jupiter, but this limit is only half the reported best-fit mass of the planet as originally claimed. The claims for this planet thus fall into a long history of claimed astrometric extrasolar planet
Extrasolar planet
An extrasolar planet, or exoplanet, is a planet outside the Solar System. A total of such planets have been identified as of . It is now known that a substantial fraction of stars have planets, including perhaps half of all Sun-like stars...
detections that were subsequently refuted.