HD 6434 b
Encyclopedia
HD 6434 b is an extrasolar planet
orbiting the star
HD 6434
. It has a minimum mass
about half that of Jupiter
. It orbits the star very close, over 2.5 times as close as Mercury
orbits the Sun. For this reason it completes one orbit in only 22 day
s. Unlike true "hot Jupiter
s" like 51 Pegasi b
, HD 6434 b does not have a circular orbit, but rather an eccentric one.
By studying observations taken by the Hipparcos
astrometric
mission, a group of scientists proposed that the planet has an inclination
of 179.9° (almost exactly face-on) and a mass of 196 Jupiters. If that was the case, the planet would be a red dwarf
instead. However, the data was anything but conclusive, and statistically
it is extremely unlikely to lie in such a position. But because the inclination is unknown, so is the true mass
of the planet. Still, it is very probable that the object is a true 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...
orbiting the 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...
HD 6434
HD 6434
HD 6434 is an 8th magnitude star in the constellation of Phoenix. It is a very Sun-like yellow dwarf star, but younger, being 3,200 million years old. Yellow dwarfs are not very luminous, so at a distance of 130 light years it is not visible to the unaided eye. With binoculars it is readily visible...
. It has a 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...
about half 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,...
. It orbits the star very close, over 2.5 times as close as 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...
orbits the Sun. For this reason it completes one orbit in only 22 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. Unlike true "hot Jupiter
Hot Jupiter
Hot Jupiters are a class of extrasolar planet whose mass is close to or exceeds that of Jupiter...
s" like 51 Pegasi b
51 Pegasi b
51 Pegasi b , sometimes though unofficially named Bellerophon, is an extrasolar planet approximately 50 light-years away in the constellation of Pegasus...
, HD 6434 b does not have a circular orbit, but rather an eccentric one.
By studying observations taken by 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...
astrometric
Astrometry
Astrometry is the branch of astronomy that involves precise measurements of the positions and movements of stars and other celestial bodies. The information obtained by astrometric measurements provides information on the kinematics and physical origin of our Solar System and our Galaxy, the Milky...
mission, a group of scientists proposed that the planet has an 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 179.9° (almost exactly face-on) and a mass of 196 Jupiters. If that was the case, the planet would be a 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....
instead. However, the data was anything but conclusive, and statistically
Statistics
Statistics is the study of the collection, organization, analysis, and interpretation of data. It deals with all aspects of this, including the planning of data collection in terms of the design of surveys and experiments....
it is extremely unlikely to lie in such a position. But because the inclination is unknown, so is the true mass
True mass
The term true mass is synonymous with the term mass, but is used in astronomy to differentiate the measured mass of a planet from the lower limit of mass usually obtained from radial velocity techniques...
of the planet. Still, it is very probable that the object is a true planet.