HD 10180
Encyclopedia
HD 10180 is a solar-type star
. A research team led by Christophe Lovis of the University of Geneva
discovered that the star has at least five planets
, and possibly as many as seven. It is 127 light-year
s away, in the southern constellation of Hydrus
. The mass and metallicity
of HD 10180 are 6% and 20% greater than the values of the Sun
.
The system contains five planets with minimum mass
es from 12 to 25 times Earth's (comparable to the mass of the ice giant
planets Uranus
and Neptune
in our Solar System) at orbital radii of 0.06, 0.13, 0.27, 0.49 and 1.42 AU
. The false detection probabilities for these five planets are all much less than 0.1%. In addition, there is a possible Earth
-sized planet located at 0.02 AU (minimum mass 1.4 times Earth's; spurious detection probability 1.4%), and a possible Saturn
-sized giant planet at 3.4 AU (minimum mass 65 times Earth's; spurious detection probability 0.6%). This represents the largest number of planets detected in an extrasolar planetary system
(the previous record holder, the 55 Cancri
system, has five).
HD 10180's five Neptune-sized planets have orbital radii ranging from one sixth that of Mercury
to just short of that of Mars
. The innermost planet, while Earth-like in diameter, has an orbital radius about one-seventeenth that of Mercury, and would be correspondingly hotter. The outermost planet revolves at a distance from HD 10180 comparable to the distance of the outer part of the asteroid belt
from our Sun.
The planetary system contains no planets in mean motion resonances
, although it has a number of near resonances. The approximate ratios of periods of adjacent orbits are (proceeding outward): 1:5, 1:3, 1:3, 2:5, 1:5, 3:11.
The planets were detected using the HARPS
spectrograph
, in conjunction with the ESO
's 3.6 m telescope at La Silla Observatory
in Chile
, using Doppler spectroscopy
. Since the inclination
of the planets' orbits is unknown, only minimum planetary masses can presently be obtained. Dynamical simulations suggest that the system cannot be stable if the true masses of the planets exceed the minimum masses by a factor of greater than three (corresponding to an inclination of less than 20°, where 90° is edge-on).
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...
. A research team led by Christophe Lovis of the University of Geneva
University of Geneva
The University of Geneva is a public research university located in Geneva, Switzerland.It was founded in 1559 by John Calvin, as a theological seminary and law school. It remained focused on theology until the 17th century, when it became a center for Enlightenment scholarship. In 1873, it...
discovered that the star has at least five planets
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...
, and possibly as many as seven. It is 127 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, in the southern constellation of Hydrus
Hydrus
Hydrus is a small constellation in the southern sky, created in the sixteenth century. Its name means "male water snake", and it should not be confused with Hydra, a much larger constellation which represents a female water snake.-History:...
. The mass and metallicity
Metallicity
In astronomy and physical cosmology, the metallicity of an object is the proportion of its matter made up of chemical elements other than hydrogen and helium...
of HD 10180 are 6% and 20% greater than the values 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...
.
The system contains five planets with minimum mass
Minimum mass
In astronomy, minimum mass is the lower-bound calculated mass of observed objects such as planets, stars and binary systems, nebulae, and black holes. Minimum mass is a widely cited statistic for extrasolar planets...
es from 12 to 25 times Earth's (comparable to the mass of the ice giant
Ice giant
Ice Giant or Ice giants may refer to:* A type of gas giant composed largely of materials less volatile than hydrogen and helium* The frost giants of Norse mythology, see also Hrimthurs...
planets Uranus
Uranus
Uranus is the seventh planet from the Sun. It has the third-largest planetary radius and fourth-largest planetary mass in the Solar System. It is named after the ancient Greek deity of the sky Uranus , the father of Cronus and grandfather of Zeus...
and 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...
in our Solar System) at orbital radii of 0.06, 0.13, 0.27, 0.49 and 1.42 AU
Astronomical unit
An astronomical unit is a unit of length equal to about or approximately the mean Earth–Sun distance....
. The false detection probabilities for these five planets are all much less than 0.1%. In addition, there is a possible 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...
-sized planet located at 0.02 AU (minimum mass 1.4 times Earth's; spurious detection probability 1.4%), and a possible 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,...
-sized giant planet at 3.4 AU (minimum mass 65 times Earth's; spurious detection probability 0.6%). This represents the largest number of planets detected in an extrasolar planetary system
Planetary system
A planetary system consists of the various non-stellar objects orbiting a star such as planets, dwarf planets , asteroids, meteoroids, comets, and cosmic dust...
(the previous record holder, the 55 Cancri
55 Cancri
55 Cancri , also cataloged Rho1 Cancri or abbreviated 55 Cnc, is a binary star approximately 41 light-years away from Earth in the constellation of Cancer...
system, has five).
HD 10180's five Neptune-sized planets have orbital radii ranging from one sixth that of Mercury
Mercury (planet)
Mercury is the innermost and smallest planet in the Solar System, orbiting the Sun once every 87.969 Earth days. The orbit of Mercury has the highest eccentricity of all the Solar System planets, and it has the smallest axial tilt. It completes three rotations about its axis for every two orbits...
to just short of that of Mars
Mars
Mars is the fourth planet from the Sun in the Solar System. The planet is named after the Roman god of war, Mars. It is often described as the "Red Planet", as the iron oxide prevalent on its surface gives it a reddish appearance...
. The innermost planet, while Earth-like in diameter, has an orbital radius about one-seventeenth that of Mercury, and would be correspondingly hotter. The outermost planet revolves at a distance from HD 10180 comparable to the distance of the outer part of the asteroid belt
Asteroid belt
The asteroid belt is the region of the Solar System located roughly between the orbits of the planets Mars and Jupiter. It is occupied by numerous irregularly shaped bodies called asteroids or minor planets...
from our Sun.
Planetary system
The planetary system contains no planets in mean motion resonances
Orbital resonance
In celestial mechanics, an orbital resonance occurs when two orbiting bodies exert a regular, periodic gravitational influence on each other, usually due to their orbital periods being related by a ratio of two small integers. Orbital resonances greatly enhance the mutual gravitational influence of...
, although it has a number of near resonances. The approximate ratios of periods of adjacent orbits are (proceeding outward): 1:5, 1:3, 1:3, 2:5, 1:5, 3:11.
The planets were detected using the HARPS
High Accuracy Radial Velocity Planet Searcher
The High Accuracy Radial velocity Planet Searcher is a high-precision echelle spectrograph installed in 2002 on ESO's 3.6m telescope at La Silla Observatory in Chile. The first light was achieved in February 2003...
spectrograph
Spectrograph
A spectrograph is an instrument that separates an incoming wave into a frequency spectrum. There are several kinds of machines referred to as spectrographs, depending on the precise nature of the waves...
, in conjunction with the ESO
European Southern Observatory
The European Southern Observatory is an intergovernmental research organisation for astronomy, supported by fifteen countries...
's 3.6 m telescope at La Silla Observatory
La Silla Observatory
La Silla Observatory is an astronomical observatory in Chile with three telescopes built and operated by the European Southern Observatory organisation, and several others are partly maintained by ESO...
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...
, 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....
. Since the inclination
Inclination
Inclination in general is the angle between a reference plane and another plane or axis of direction.-Orbits:The inclination is one of the six orbital parameters describing the shape and orientation of a celestial orbit...
of the planets' orbits is unknown, only minimum planetary masses can presently be obtained. Dynamical simulations suggest that the system cannot be stable if the true masses of the planets exceed the minimum masses by a factor of greater than three (corresponding to an inclination of less than 20°, where 90° is edge-on).