Upsilon Andromedae e is the proposed outermost
extrasolar planet
An exoplanet or extrasolar planet is a planet outside the Solar System. The first possible evidence of an exoplanet was noted in 1917 but was not recognized as such. The first confirmation of detection occurred in 1992. A different planet, init ...
orbiting the star
Upsilon Andromedae
Upsilon Andromedae (υ Andromedae, abbreviated Upsilon And, υ And) is a binary star located 44 light-years from Earth in the constellation of Andromeda. The system consists of an F-type main-sequence star (designated υ Andromedae A, of ...
in the
constellation of
Andromeda. If it exists, this planet would be one of the most
Jupiter
Jupiter is the fifth planet from the Sun and the largest in the Solar System. It is a gas giant with a mass more than two and a half times that of all the other planets in the Solar System combined, but slightly less than one-thousandth t ...
-like exoplanets found in terms of mass and
semi-major axis. However, subsequent studies have found that the apparent planetary signal is more likely to be an instrumental artifact.
[
]
Discovery
This planet was discovered on November 22, 2010, but the discovery paper was not released until December 2.Gliese 876 e
Gliese 876 e is an exoplanet 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 ...
, HD 10180 e, and HR 8799 e
HR 8799 e is a large exoplanet, orbiting the star HR 8799, which lies 129 light-years from Earth. This gas giant is between 5 and 10 times the mass of Jupiter, the largest planet in the Planetary System. Due to their young age and high temperat ...
; in no earlier year during the exoplanet era had more than one fourth planet been discovered.
Subsequent studies in 2011 and 2014, while finding some evidence for a fourth planet, found large inconsistencies in the estimated orbital period of Upsilon Andromedae e depending on what dataset was used,[
Astronomers initially thought that a fourth planet in this system 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
If it exists, Upsilon Andromedae e would have a 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 detected by the radial veloci ...
slightly greater than Jupiter's and orbit at a similar distance as Jupiter from the Sun, at compared to for Jupiter. Although only the 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 detected by the radial veloci ...
is determined since inclination is not yet known, its true 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 detected by the radial veloci ...
might be much greater. It would take over a decade to orbit the star. At an eccentricity of 0.00536, the planet's orbit would be more circular than that of any of the planets in the Solar System
The Solar System Capitalization of the name varies. The International Astronomical Union, the authoritative body regarding astronomical nomenclature, specifies capitalizing the names of all individual astronomical objects but uses mixed "Solar ...
.
See also
* HIP 11915 b – another Jupiter analog discovered in 2015
References
{{DEFAULTSORT:Upsilon Andromedae e
Upsilon Andromedae
Exoplanets discovered in 2010
Exoplanets detected by radial velocity
Giant planets
Exoplanet candidates