HD 217107 c
Encyclopedia
HD 217107 c is an extrasolar planet
approximately 64 light-year
s away from Earth in the constellation
of Pisces
(the Fish
). The planet was the second planet to be discovered orbiting the star HD 217107
. HD 217107 c's existence was hypothesized in 1998 and confirmed in 2005, when radial velocity studies of the star indicated another, more distant and massive companion orbiting the star. The planet is though to be a Jupiter twin
planet, but its mass and orbital parameters remain highly uncertain.
of HD 217107 carried out in 1998 revealed that its motion along the line of sight varied over a 7.1 day cycle, indicating the presence of a planet in orbit around the star. The planet was designated HD 217107 b
, and was found to be somewhat heavier than Jupiter
, and orbiting extremely close to the parent star in an orbit with quite a large eccentricity.
Most planets with orbital periods of less than 10 days have almost circular orbits, and its discoverers proposed that the high eccentricity of HD 217107 b's orbit could be due to the gravitational influence of a second planet in the system at a distance of several astronomical unit
s (AU). Confirmation of the existence of the second planet followed in 2005, and it was designated HD 217107 c.
Observations of the star's radial velocity variations indicate a period of about 8 years, and HD 217107 c's mass is thought to be at least twice that of Jupiter
in a very eccentric orbit with a semimajor axis of about 4 AU. Large uncertainties still exist in these measurements, though, due to the length of the orbital period and the distance of HD 217107 c from its parent star.
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...
approximately 64 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 from Earth 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 Pisces
Pisces (constellation)
Pisces is a constellation of the zodiac. Its name is the Latin plural for fish, and its symbol is . It lies between Aquarius to the west and Aries to the east...
(the Fish
Fish
Fish are a paraphyletic group of organisms that consist of all gill-bearing aquatic vertebrate animals that lack limbs with digits. Included in this definition are the living hagfish, lampreys, and cartilaginous and bony fish, as well as various extinct related groups...
). The planet was the second planet to be discovered orbiting the star HD 217107
HD 217107
HD 217107 is a yellow subgiant star approximately 65 light-years away from Earth in the constellation of Pisces . Its mass is very similar to the Sun's, although it is considerably older...
. HD 217107 c's existence was hypothesized in 1998 and confirmed in 2005, when radial velocity studies of the star indicated another, more distant and massive companion orbiting the star. The planet is though to be a Jupiter twin
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,...
planet, but its mass and orbital parameters remain highly uncertain.
Detection and discovery
A study of the radial velocityRadial 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...
of HD 217107 carried out in 1998 revealed that its motion along the line of sight varied over a 7.1 day cycle, indicating the presence of a planet in orbit around the star. The planet was designated HD 217107 b
HD 217107 b
HD 217107 b is an extrasolar planet approximately 64 light-years away from Earth in the constellation of Pisces . The planet was discovered orbiting the star HD 217107 approximately every seven days, classifying the planet as a hot Jupiter...
, and was found to be somewhat heavier 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,...
, and orbiting extremely close to the parent star in an orbit with quite a large eccentricity.
Most planets with orbital periods of less than 10 days have almost circular orbits, and its discoverers proposed that the high eccentricity of HD 217107 b's orbit could be due to the gravitational influence of a second planet in the system at a distance of several astronomical unit
Astronomical unit
An astronomical unit is a unit of length equal to about or approximately the mean Earth–Sun distance....
s (AU). Confirmation of the existence of the second planet followed in 2005, and it was designated HD 217107 c.
Observations of the star's radial velocity variations indicate a period of about 8 years, and HD 217107 c's mass is thought to be at least twice 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,...
in a very eccentric orbit with a semimajor axis of about 4 AU. Large uncertainties still exist in these measurements, though, due to the length of the orbital period and the distance of HD 217107 c from its parent star.
See also
- HD 217107HD 217107HD 217107 is a yellow subgiant star approximately 65 light-years away from Earth in the constellation of Pisces . Its mass is very similar to the Sun's, although it is considerably older...
- HD 217107 bHD 217107 bHD 217107 b is an extrasolar planet approximately 64 light-years away from Earth in the constellation of Pisces . The planet was discovered orbiting the star HD 217107 approximately every seven days, classifying the planet as a hot Jupiter...
- 47 Ursae Majoris b47 Ursae Majoris b47 Ursae Majoris b is an extrasolar planet approximately 46 light-years from Earth in the constellation of Ursa Major. The planet was discovered located in a long-period orbit around the star 47 Ursae Majoris in January 1996 and as of 2011 is the innermost of three known planets in its planetary...