HW Virginis
Encyclopedia
HW Virginis, abbreviated HW Vir, is an eclipsing binary system (of the Algol type
) approximately 590 light-year
s away (based on the stellar properties and magnitudes: the Hipparcos
trigonometric parallax measurement has too high an error value to be useful) in the constellation
of Virgo
. The system comprises an eclipsing B-type subdwarf
star and red dwarf
star. The two stars orbit each other every 0.116795 day
s.
has a mass at least 8.47 times the mass of Jupiter
and takes just over 9 years to complete an orbit. The outer companion HW virginis b takes 15.8 years to complete an orbit and has a mass at least 19.2 times Jupiter's mass. According to the definition used by the International Astronomical Union
's Working Group on Extrasolar Planets, the inner companion would be classified as a planet
, while the outer companion would be classified as a brown dwarf
. However the discoverers note that the orbital configuration suggests that the objects formed as planets in a disc, and the formation of planets above the deuterium fusion limit has been predicted by computer models of giant planet formation.
Algol variable
Algol variables or Algol-type binaries are a class of eclipsing binary stars where the orbital plane of the stars are coincident with the line of sight from Earth. When the cooler component passes in front of the hotter one, part of the latter's light is blocked, and the total brightness of the...
) approximately 590 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 (based on the stellar properties and magnitudes: the 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...
trigonometric parallax measurement has too high an error value to be useful) 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 Virgo
Virgo (constellation)
Virgo is one of the constellations of the zodiac. Its name is Latin for virgin, and its symbol is . Lying between Leo to the west and Libra to the east, it is the second largest constellation in the sky...
. The system comprises an eclipsing B-type subdwarf
Subdwarf B star
The subdwarf B star is a kind of subdwarf star with spectral type B. They differ from the typical subdwarf star by being much hotter and brighter. They are from the "extreme horizontal branch stars" of the Hertzsprung–Russell diagram...
star and 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. The two stars orbit each other every 0.116795 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.
Planetary system
In addition, the system has two substellar companions in orbit around the binary: the inner companion HW Virginis cHW Virginis c
HW Virginis c is an extrasolar planet located approximately 590 light years away in the constellation of Virgo, orbiting the 11th magnitude eclipsing binary star HW Virginis. This planet is very massive, at least 8.47 times more than Jupiter. This is a long-period planet with an orbital revolution...
has a mass at least 8.47 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,...
and takes just over 9 years to complete an orbit. The outer companion HW virginis b takes 15.8 years to complete an orbit and has a mass at least 19.2 times Jupiter's mass. According to the definition used by the International Astronomical Union
International Astronomical Union
The International Astronomical Union IAU is a collection of professional astronomers, at the Ph.D. level and beyond, active in professional research and education in astronomy...
's Working Group on Extrasolar Planets, the inner companion would be classified as a 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,...
, while the outer companion would be classified 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...
. However the discoverers note that the orbital configuration suggests that the objects formed as planets in a disc, and the formation of planets above the deuterium fusion limit has been predicted by computer models of giant planet formation.
See also
- Algol
- CM DraconisCM DraconisCM Draconis is an eclipsing binary system approximately 47 light-years away in the constellation of Draco . The system consists of two nearly identical red dwarf stars located in the constellation Draco. The two stars orbit each other with a period of 1.27 days with a separation of 2.7 million...
- QS VirginisQS VirginisQS Virginis is an eclipsing binary system approximately 157 light-years away from Sun, forming a cataclysmic variable...
- NN SerpentisNN SerpentisNN Serpentis is an eclipsing binary system approximately 1670 light-years away, likely a cataclysmic variable star. The system comprises an eclipsing white dwarf star and red dwarf star...
- List of extrasolar planets