Kepler-421b

Kepler-421b is an exoplanet that, as of July 2014, has the longest known year of any transiting planet (704 days),[1] although not as long as the planets that have been directly imaged, or many of the planets found by the radial-velocity method, or as long as some transiting planet candidates which are listed as planets in the Extrasolar Planets Encyclopaedia (KIC 5010054 b etc.).[2] It is the first transiting-planet found near the snow-line.

Kepler-421b
Discovery
Discovery siteKepler telescope
Discovery date2014
Transit
Orbital characteristics
1.219 AU (182,400,000 km)
704.1984 d
Inclination89.965
StarKepler-421
Physical characteristics
Mean radius
4.16 R⊕
    Planets with long years
    Currently the known directly imaged planets are far from their star so have long years: GU-Piscium-b's year is 163,000 years long. The directly imaged planet with the shortest year is Beta-Pictoris-b with a year that takes 20 years. The transiting planets known so far are close to their stars: The transiting planet with the longest year is Kepler-421b with a year that lasts 704 days or about 2 years.[1]

    Normally, at least three transits are required to confirm a planet. Due to very high signal to noise ratio, only two transits were sufficient to validate Kepler-421b to be a real planet without additional confirmation methods.

    Kepler-421b is slightly larger than Uranus although its mass is not known.

    References
    1. Johnson, Michele (July 21, 2014). "Astronomers Discover Transiting Exoplanet with Longest Known Year". NASA. Retrieved July 25, 2014.
    2. http://exoplanet.eu/catalog/?f=%22transit%22+IN+detection

    Further reading


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