{{Short description|Extrasolar planet}} {{Infobox planet | name = Kepler-421b <!-- DISCOVERY -->| discovery_site = Kepler telescope | discovered = 2014 | discovery_method = Transit <!-- DESIGNATIONS --> <!-- ORBITAL -->| apsis = astron | semimajor = {{convert|1.219|AU|km|abbr=on}} | period = 704.1984 d | inclination = 89.965 | star = Kepler-421 <!-- PHYS CHARS -->| mean_radius = 4.16 {{Earth radius|link=y}} <!-- ATMOSPHERE --> <!-- NOTES -->| mass = 16.1 M<sub>🜨</sub> }} '''Kepler-421b''' is an exoplanet that, as of July 2014,<ref>{{citation|arxiv=1407.4807|year=2014|title=Discovery of a Transiting Planet Near the Snow-Line|doi=10.1088/0004-637X/795/1/25|last1=Kipping|first1=D. M.|last2=Torres|first2=G.|last3=Buchhave|first3=L. A.|last4=Kenyon|first4=S. J.|last5=Henze|first5=C.|last6=Isaacson|first6=H.|last7=Kolbl|first7=R.|last8=Marcy|first8=G. W.|last9=Bryson|first9=S. T.|last10=Stassun|first10=K.|last11=Bastien|first11=F.|journal=The Astrophysical Journal|volume=795|issue=1|page=25|bibcode=2014ApJ...795...25K|s2cid=119240746}}</ref> has the longest known year of any transiting planet (704 days),<ref name="NASA-20140721">{{cite web |last=Johnson |first=Michele |title=Astronomers Discover Transiting Exoplanet with Longest Known Year |url=http://www.nasa.gov/ames/kepler/transiting-exoplanet-with-longest-known-year |date=July 21, 2014 |work=NASA |accessdate=July 25, 2014 |archive-date=April 17, 2018 |archive-url=https://web.archive.org/web/20180417220605/https://www.nasa.gov/ames/kepler/transiting-exoplanet-with-longest-known-year/ |url-status=dead }}</ref> 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.).<ref>{{cite web | url=https://exoplanet.eu/catalog/?f=%22transit%22+IN+detection/ | work=Extrasolar Planets Encyclopaedia | title=The Extrasolar Planet Encyclopaedia — Catalog Listing }}</ref> It is the first transiting-planet found near the snow-line.
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, and having a mass 16.1 times<ref>{{Cite web |title=Kepler-421 b - NASA Science |url=https://science.nasa.gov/exoplanet-catalog/kepler-421-b/ |access-date=2024-12-19 |website=science.nasa.gov |language=en-US}}</ref> that of Earth, typical of an ice giant.
==References== {{reflist}}
==Further reading== {{div col|colwidth=20em}} *[http://www.slate.com/blogs/bad_astronomy/2014/07/23/kepler_421b_exoplanet_with_longest_orbital_period_found.html The Longest Year], Phil Plait, Slate, July 23, 2014 *[http://www.popularmechanics.com/how-to/blog/new-exoplanet-has-the-longest-year-ever-discovered-17016042?click=pm_latest New Exoplanet Has the Longest Year Ever Discovered], July 23, 2014 at 2:15:00 PM by Niko Vercelletto, Popular Mechanics *[http://www.gizmag.com/exoplanet-longest-year-kepler/33078/ Astronomers discover exoplanet with longest known year], Anthony Wood, July 23, 2014, Gizmag *[http://www.universetoday.com/113372/first-exoplanet-discovered-beyond-the-snow-line/ First Exoplanet Discovered Beyond the “Snow Line”], by Shannon Hall on July 22, 2014, Universe Today *[http://www.redorbit.com/news/space/1113195768/kepler-planet-has-longest-known-year-072214 Transiting Exoplanet With Longest Known Year Discovered By Kepler Mission] {{Webarchive|url=https://web.archive.org/web/20160307224313/http://www.redorbit.com/news/space/1113195768/kepler-planet-has-longest-known-year-072214 |date=2016-03-07 }}, July 22, 2014, RedOrbit *[https://arxiv.org/abs/1407.4807 Discovery of a Transiting Planet Near the Snow-Line], David M. Kipping, Guillermo Torres, Lars A. Buchhave, Scott J. Kenyon, Christopher E. Henze, Howard Isaacson, Rea Kolbl, Geoff W. Marcy, Stephen T. Bryson, Keivan G. Stassun, Fabienne A. Bastien, (Submitted on 17 Jul 2014) {{div col end}} {{2014 in space}}
Category:Exoplanets discovered in 2014 Category:Transiting exoplanets 421b
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