HD 210277 b
Encyclopedia
HD 210277 b is an extrasolar planet
orbiting the star HD 210277
. It was discovered in September 1998 by the California and Carnegie Planet Search team using the highly successful radial velocity
method. The planet is at least 24% more massive than Jupiter
. The mean distance of the planet from the star is slightly more than Earth's
distance from the Sun. However, the orbit is very eccentric, so at periastron
this distance is almost halved, and at apastron
it is as distant as Mars
is from the Sun.
In 2000, a group of scientists proposed, based on preliminary data from the Hipparcos
astrometrical
satellite
, that the planet would have an inclination of 175.8° and a true mass
of 18 times Jupiter making it a brown dwarf
instead of a planet. However these measurements were later proved useful only for upper limits of inclination. If the planet orbits in the same plane as the claimed circumstellar disk, which seems a plausible assumption, it would have an inclination
of 40° and an absolute mass of 2.2 times Jupiter, however later observations failed to confirm the disk's existence.
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 HD 210277
HD 210277
HD 210277 is a 7th magnitude star in the constellation of Aquarius. It is a yellow dwarf star with a mass around 0.92 times that of our Sun. Since its distance is about 69 light years, it is not visible to the unaided eye. With binoculars it is easily visible.The star has a massive extrasolar...
. It was discovered in September 1998 by the California and Carnegie Planet Search team using the highly successful radial velocity
Radial velocity
Radial velocity is the velocity of an object in the direction of the line of sight . In astronomy, radial velocity most commonly refers to the spectroscopic radial velocity...
method. The planet is at least 24% more massive than 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 mean distance of the planet from the star is slightly more than Earth's
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...
distance from the Sun. However, the orbit is very eccentric, so at periastron
Apsis
An apsis , plural apsides , is the point of greatest or least distance of a body from one of the foci of its elliptical orbit. In modern celestial mechanics this focus is also the center of attraction, which is usually the center of mass of the system...
this distance is almost halved, and at apastron
Apsis
An apsis , plural apsides , is the point of greatest or least distance of a body from one of the foci of its elliptical orbit. In modern celestial mechanics this focus is also the center of attraction, which is usually the center of mass of the system...
it is as distant as 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...
is from the Sun.
In 2000, a group of scientists proposed, based on preliminary data from 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...
astrometrical
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...
satellite
Satellite
In the context of spaceflight, a satellite is an object which has been placed into orbit by human endeavour. Such objects are sometimes called artificial satellites to distinguish them from natural satellites such as the Moon....
, that the planet would have an inclination of 175.8° and a 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 18 times Jupiter making it 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...
instead of a planet. However these measurements were later proved useful only for upper limits of inclination. If the planet orbits in the same plane as the claimed circumstellar disk, which seems a plausible assumption, it would have 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 40° and an absolute mass of 2.2 times Jupiter, however later observations failed to confirm the disk's existence.
