Gliese 570
Encyclopedia
Gliese 570, also known as 33 G. Librae, is a ternary star system
approximately 19 light-year
s away. The primary star is an orange dwarf
star
(much dimmer and smaller than the Sun
). The other secondary stars are themselves a binary system
, two red dwarf
s that orbit one another. A brown dwarf
has been confirmed to be orbiting in the system. As of 1998, an extrasolar planet
was thought to orbit the primary star, but it was discounted in 2000.
. The system is southwest of Alpha Librae
and northwest of Sigma Librae
. In the early 1990s, the European Hipparcos
mission measured the parallax
of components B and C, suggesting that the system was at a distance of 24.4 light-year
s from the Sun
. This, however, was a relatively large error as Earth-based parallax and orbit observations suggest that the two stars are actually part of a system with Gliese 570 A, and must actually lie at the same distance.
star that may just have over three fourths the mass
of the Sun
, about 77 percent of its radius
, and only 15.6 percent of its luminosity
. It has a separation of 190 astronomical unit
s from the binary components B and C, moving in an eccentric
orbit that takes at least 2130 years to complete. Gliese 570 A is spectral type K4V and emits X-rays.
A binary system in their own right, components B and C are both rather dim red dwarf
stars that have less mass, radius, and luminosity than the Sun
. Component B is spectral type M1V, component C is spectral type M3V, and both emit X-rays.
On January 15, 2000, astronomers announced that they had found one of the coolest brown dwarfs then known. Catalogued as Gliese 570 D (or rarely Gliese 570 d), it was observed at a wide separation of more than 1,500 astronomical unit from the triple star system. It has an estimated mass of 50 times that of Jupiter
.
The status of Gliese 570 D as a brown dwarf
was confirmed by Doppler spectroscopy
at the Cerro Tololo Interamerican Observatory in Chile
. The surface temperature of this substellar object was found to be a relatively cool 500 degrees Celsius, making it cooler and less luminous than any other known brown dwarf (including the prototype "T" dwarf), and classifying the object as a T7-8V brown dwarf. No X-rays have been reported from this brown dwarf
.
was announced to orbit the primary star within the Gliese 570 system. The planet, identified as "Gliese 570 Ab", was considered doubtful and the claim was retracted in 2000. No extrasolar planets have been confirmed to exist in this multiple star system thus far.
Multiple star
A multiple star consists of three or more stars which appear from the Earth to be close to one another in the sky. This may result from the stars being physically close and gravitationally bound to each other, in which case it is physical, or this closeness may be merely apparent, in which case...
approximately 19 light-year
Light-year
A light-year, also light year or lightyear is a unit of length, equal to just under 10 trillion kilometres...
s away. The primary star is an orange dwarf
Orange dwarf
A K-type main-sequence star , also referred to orange dwarf, are main-sequence stars of spectral type K and luminosity class V. These stars are intermediate in size between red M-type main-sequence stars and yellow G-type main-sequence stars...
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...
(much dimmer and smaller 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...
). The other secondary stars are themselves a 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...
, two 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....
s that orbit one another. 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...
has been confirmed to be orbiting in the system. As of 1998, an 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...
was thought to orbit the primary star, but it was discounted in 2000.
Distance and visibility
In the night sky, the Gliese 570 system lies in the southwestern part of LibraLibra (constellation)
Libra is a constellation of the zodiac. Its name is Latin for weighing scales, and its symbol is . It is fairly faint, with no first magnitude stars, and lies between Virgo to the west and Scorpius to the east.-Notable features:]...
. The system is southwest of Alpha Librae
Alpha Librae
Alpha Librae is the second brightest star in the constellation Libra . It has the traditional name Zubenelgenubi. The name, from Arabic الزبن الجنوبي , means "southern claw" and was coined before Libra was recognized as distinct from Scorpius...
and northwest of Sigma Librae
Sigma Librae
Sigma Librae is a star in the constellation Libra. It has the traditional names Brachium , Cornu , and Zubenalgubi ....
. In the early 1990s, the European Hipparcos
Hipparcos
Hipparcos was a scientific mission of the European Space Agency , launched in 1989 and operated between 1989 and 1993. It was the first space experiment devoted to precision astrometry, the accurate measurement of the positions of celestial objects on the sky...
mission measured the 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"...
of components B and C, suggesting that the system was at a distance of 24.4 light-year
Light-year
A light-year, also light year or lightyear is a unit of length, equal to just under 10 trillion kilometres...
s from 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...
. This, however, was a relatively large error as Earth-based parallax and orbit observations suggest that the two stars are actually part of a system with Gliese 570 A, and must actually lie at the same distance.
Star system
The primary star of the system (component A) is an orange dwarfOrange dwarf
A K-type main-sequence star , also referred to orange dwarf, are main-sequence stars of spectral type K and luminosity class V. These stars are intermediate in size between red M-type main-sequence stars and yellow G-type main-sequence stars...
star that may just have over three fourths the mass
Mass
Mass can be defined as a quantitive measure of the resistance an object has to change in its velocity.In physics, mass commonly refers to any of the following three properties of matter, which have been shown experimentally to be equivalent:...
of 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...
, about 77 percent of its radius
Radius
In classical geometry, a radius of a circle or sphere is any line segment from its center to its perimeter. By extension, the radius of a circle or sphere is the length of any such segment, which is half the diameter. If the object does not have an obvious center, the term may refer to its...
, and only 15.6 percent of its luminosity
Luminosity
Luminosity is a measurement of brightness.-In photometry and color imaging:In photometry, luminosity is sometimes incorrectly used to refer to luminance, which is the density of luminous intensity in a given direction. The SI unit for luminance is candela per square metre.The luminosity function...
. It has a separation of 190 astronomical unit
Astronomical unit
An astronomical unit is a unit of length equal to about or approximately the mean Earth–Sun distance....
s from the binary components B and C, moving in an eccentric
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...
orbit that takes at least 2130 years to complete. Gliese 570 A is spectral type K4V and emits X-rays.
A binary system in their own right, components B and C are both rather dim 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....
stars that have less mass, radius, and luminosity 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...
. Component B is spectral type M1V, component C is spectral type M3V, and both emit X-rays.
On January 15, 2000, astronomers announced that they had found one of the coolest brown dwarfs then known. Catalogued as Gliese 570 D (or rarely Gliese 570 d), it was observed at a wide separation of more than 1,500 astronomical unit from the triple star system. It has an estimated mass of 50 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,...
.
The status of Gliese 570 D as 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...
was confirmed by 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....
at the Cerro Tololo Interamerican Observatory in Chile
Chile
Chile ,officially the Republic of Chile , is a country in South America occupying a long, narrow coastal strip between the Andes mountains to the east and the Pacific Ocean to the west. It borders Peru to the north, Bolivia to the northeast, Argentina to the east, and the Drake Passage in the far...
. The surface temperature of this substellar object was found to be a relatively cool 500 degrees Celsius, making it cooler and less luminous than any other known brown dwarf (including the prototype "T" dwarf), and classifying the object as a T7-8V brown dwarf. No X-rays have been reported from this 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...
.
Claims of a planetary system
In 1998, an extrasolar planetExtrasolar 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...
was announced to orbit the primary star within the Gliese 570 system. The planet, identified as "Gliese 570 Ab", was considered doubtful and the claim was retracted in 2000. No extrasolar planets have been confirmed to exist in this multiple star system thus far.
See also
- Epsilon IndiEpsilon IndiEpsilon Indi is a K-type main-sequence star approximately 12 light-years away in the constellation of Indus. Two brown dwarfs, found in 2003, orbit the star.- Observation :...
- Gliese 229Gliese 229Gliese 229 is a red dwarf star about 19 light years away in the constellation Lepus. It has 58% of the mass of the Sun, 69% of the Sun's radius, and a very low projected rotation velocity of 1 km/s at the stellar equator.The star is known to be a low activity flare star, which means it...
- HD 188753HD 188753HD 188753 is a triple star system approximately 149 light-years away in the constellation of Cygnus . In 2005, an extrasolar planet was announced to be orbiting the primary star in the system...
- Iota HorologiiIota HorologiiIota Horologii is a solar twin, yellow dwarf star approximately 56 light-years away in the constellation of Horologium . The star is classified as a G0Vp yellow dwarf...
- Phi2 PavonisPhi2 PavonisPhi² Pavonis , also known as HD 196378, is a yellow-white dwarf star approximately 82 light-years away in the constellation of Pavo . It is evolving into a subgiant....