Upsilon Andromedae e
Encyclopedia
Upsilon Andromedae e is the outermost extrasolar planet
orbiting the star Upsilon Andromedae
in the constellation of Andromeda
. This planet is more Jupiter-like than any other known exoplanet.
, the others being Gliese 876 e
, HD 10180 e, and HR 8799 e; in no other year so far during the exoplanet era has more than one fourth planet been discovered.
Astronomers originally thought that this planet could not exist because it would have made the planetary system unstable and would have been ejected. But in 2007, an island region of stability was reported where a fourth planet could exist.
slightly greater than Jupiter's and orbits at a similar distance as Jupiter from the Sun, at precisely 5.2456 AU compared to 5.2043 AU for Jupiter. Although only the minimum mass
is determined since inclination is not yet known, its true mass
might be much greater. It takes over a decade to orbit the star. At an eccentricity of 0.00536, the planet's orbit is more circular than that of any of the planets in our solar system
.
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 Upsilon Andromedae
Upsilon Andromedae
Upsilon Andromedae is a binary star located approximately 44 light-years away from Earth in the constellation Andromeda. The primary star is a yellow-white dwarf star that is somewhat younger than the Sun...
in the constellation of Andromeda
Andromeda (constellation)
Andromeda is a constellation in the northern sky. It is named after Andromeda, the princess in the Greek legend of Perseus who was chained to a rock to be eaten by the sea monster Cetus...
. This planet is more Jupiter-like than any other known exoplanet.
Discovery
This planet was discovered on November 22, 2010, but the discovery paper was not released until December 2. It is the fourth time in 2010 that a fourth planet has been discovered in a planetary systemPlanetary system
A planetary system consists of the various non-stellar objects orbiting a star such as planets, dwarf planets , asteroids, meteoroids, comets, and cosmic dust...
, the others being Gliese 876 e
Gliese 876 e
Gliese 876 e is an extrasolar planet orbiting the star Gliese 876 in the constellation of Aquarius. It is in a 1:2:4 Laplace resonance with the planets Gliese 876 c and Gliese 876 b: for each orbit of planet e, planet b completes two orbits and planet c completes four...
, HD 10180 e, and HR 8799 e; in no other year so far during the exoplanet era has more than one fourth planet been discovered.
Astronomers originally thought that this planet could not exist because it would have made the planetary system unstable and would have been ejected. But in 2007, an island region of stability was reported where a fourth planet could exist.
Characteristics
Upsilon Andromedae e is a so-called “Jupiter-twin” because it has a massMass
Mass can be defined as a quantitive measure of the resistance an object has to change in its velocity.In physics, mass commonly refers to any of the following three properties of matter, which have been shown experimentally to be equivalent:...
slightly greater than Jupiter's and orbits at a similar distance as Jupiter from the Sun, at precisely 5.2456 AU compared to 5.2043 AU for Jupiter. Although only the 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...
is determined since inclination is not yet known, its 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...
might be much greater. It takes over a decade to orbit the star. At an eccentricity of 0.00536, the planet's orbit is more circular than that of any of the planets in our solar system
Solar System
The Solar System consists of the Sun and the astronomical objects gravitationally bound in orbit around it, all of which formed from the collapse of a giant molecular cloud approximately 4.6 billion years ago. The vast majority of the system's mass is in the Sun...
.