HD 82943
Encyclopedia
HD 82943 is a yellow dwarf
star
approximately 89 light-year
s away in the constellation
of Hydra
. Two extrasolar planet
s have been confirmed to be orbiting it,
and it is thought that the system had more giant planets that were "swallowed" by the parent star. HD 82943 is estimated at roughly 1.15 times the mass of the Sun.
) was announced in 2000 by a team of French
astronomers led by Michel Mayor
. The planet orbits its parent star at a mean distance of 1.19 astronomical unit
s (AU) and taking approximately 441 day
s to complete the orbit. Nearly a year later, a second planet (designated HD 82943 c
) was announced by the same discoverers of the previous planet. This planet orbits closer than the other, at a mean distance of 0.746 AU and taking 219 days to complete its orbit. The two known planets appear to have a 2:1 resonance
with one another.
Announced in 2001, HD 82943 was found to contain an unusually high amount of Lithium-6. Stars do not naturally contain Lithium-6, but unlike stars, planet
s never reach temperatures that are high enough to burn their initial content of Lithium-6 (planets should retain Lithium-6). The simplest and most convincing answer to explain this observation is that one or more planets, or at least planetary material, have fallen into the star, sometime after it passed through its early evolutionary stage.
Yellow dwarf
A G-type main-sequence star , often called a yellow dwarf, is a main-sequence star of spectral type G and luminosity class V. Such a star has about 0.8 to 1.2 solar masses and surface temperature of between 5,300 and 6,000 K., Tables VII, VIII...
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...
approximately 89 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 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....
of Hydra
Hydra (constellation)
Hydra is the largest of the 88 modern constellations, measuring 1303 square degrees. It has a long history, having been included among the 48 constellations listed by the 2nd century astronomer Ptolemy. It is commonly represented as a water snake...
. Two 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...
s have been confirmed to be orbiting it,
and it is thought that the system had more giant planets that were "swallowed" by the parent star. HD 82943 is estimated at roughly 1.15 times the mass of the Sun.
Planetary system
The first planet discovered (designated HD 82943 bHD 82943 b
HD 82943 b is an extrasolar planet approximately 89 light-years away in the constellation of Hydra. The planet was announced in 2000 by the Geneva Extrasolar Planet Search Team. The planet is the outermost planet of two....
) was announced in 2000 by a team of French
France
The French Republic , The French Republic , The French Republic , (commonly known as France , is a unitary semi-presidential republic in Western Europe with several overseas territories and islands located on other continents and in the Indian, Pacific, and Atlantic oceans. Metropolitan France...
astronomers led by Michel Mayor
Michel Mayor
Dr. Michel G. E. Mayor is a Swiss astrophysicist and professor emeritus at the University of Geneva's Department of Astronomy. He formally retired in 2007, but remains active as a researcher at the Observatory of Geneva...
. The planet orbits its parent star at a mean distance of 1.19 astronomical unit
Astronomical unit
An astronomical unit is a unit of length equal to about or approximately the mean Earth–Sun distance....
s (AU) and taking approximately 441 day
Day
A day is a unit of time, commonly defined as an interval equal to 24 hours. It also can mean that portion of the full day during which a location is illuminated by the light of the sun...
s to complete the orbit. Nearly a year later, a second planet (designated HD 82943 c
HD 82943 c
HD 82943 c is an extrasolar planet approximately 89 light-years away in the constellation of Hydra. The planet was announced in 2001 to be orbiting the yellow dwarf star HD 82943. The planet is the innermost planet of two....
) was announced by the same discoverers of the previous planet. This planet orbits closer than the other, at a mean distance of 0.746 AU and taking 219 days to complete its orbit. The two known planets appear to have a 2:1 resonance
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...
with one another.
Announced in 2001, HD 82943 was found to contain an unusually high amount of Lithium-6. Stars do not naturally contain Lithium-6, but unlike stars, 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,...
s never reach temperatures that are high enough to burn their initial content of Lithium-6 (planets should retain Lithium-6). The simplest and most convincing answer to explain this observation is that one or more planets, or at least planetary material, have fallen into the star, sometime after it passed through its early evolutionary stage.
External links
- Extrasolar Planet Interactions by Rory Barnes & Richard Greenberg, Lunar and Planetary Lab, University of Arizona