Kepler-4b

{{Short description|Extrasolar planet in the constellation Draco}} {{good article}} {{Infobox planet | name = Kepler-4b | image = Exoplanet Comparison Kepler-4 b.png | caption = Size comparison of [[Neptune]] (left) with Kepler-4b (right). | discovery_ref = <ref name="Borucki2010"/> | discovered = 2010-01-04<ref name=Talcott /> | discovery_method = [[Methods of detecting extrasolar planets#Transit photometry|Transit]] ([[Kepler Mission]])<ref name="Mission overview"/>  | apsis = astron | semimajor = {{convert|0.04558|AU|km|abbr=on}}<ref name=datatable /> | eccentricity = 0.25 ± 0.12<ref name="Kipping2010"/> | period = 3.2135<ref name=datatable /> [[day|d]] | inclination = 89.76<ref name=datatable /> | star = [[Kepler-4]]<ref name=datatable /> | mean_radius = 0.357<ref name=datatable /> {{Jupiter radius|link=y}} | mass = 0.077<ref name=datatable /> {{Jupiter mass|link=y}} | single_temperature = 1650 k<ref name=datatable />  }} '''Kepler-4b''', initially known as '''KOI 7.01''', is an [[exoplanet|extrasolar planet]] first detected as a [[astronomical transit|transit]] by the [[Kepler (spacecraft)|Kepler spacecraft]]. Its [[radius]] and [[mass]] are similar to that of [[Neptune]]; however, due to its proximity to its host star, it is substantially hotter than any planet in the Solar System.<ref name="datatable"/><ref name="sciencenews"/> The planet's discovery was announced on January 4, 2010, in [[Washington, D.C.]], along with four other planets that were initially detected by the Kepler spacecraft and subsequently confirmed by telescopes at the [[W.M. Keck Observatory]].

==Nomenclature and history== Kepler-4b was named because it was the first planet discovered in the orbit of its star, [[Kepler-4]]. The star was, in turn, named for the Kepler Mission, a [[NASA]] satellite whose purpose is to discover Earth-like planets in a section of the sky between constellations [[Cygnus (constellation)|Cygnus]] and [[Lyra]] using the transit method. Using this method, Kepler notes small and steady decreases in a star's brightness that are measured as a planet crosses in front of it.<ref name="Mission overview"/> Initially, Kepler-4b was detected as a transit event by the [[Kepler telescope]] and considered a [[Kepler Object of Interest]] with the designation KOI 7.01.<ref name="Borucki2011"/>

Subsequent [[radial velocity]] measurements by the [[High Resolution Echelle Spectrometer]] on the telescopes of W.M. Keck Observatory confirmed the planetary nature of the transit event and established a mass estimate for the planet.<ref name="Borucki2010"/> The planet's discovery was announced on January 4, 2010, along with four other planets detected by Kepler: [[Kepler-5b]], [[Kepler-6b|6b]], [[Kepler-7b|7b]] and [[Kepler-8b|8b]]<ref name="sciencenews"/> at the 215th meeting of the [[American Astronomical Society]] in Washington, D.C.<ref name=Talcott>{{cite web |url=http://cs.astronomy.com/asycs/blogs/astronomy/archive/2010/01/05/215th-aas-meeting-update-kepler-discoveries-the-talk-of-the-town.aspx |title=215th AAS meeting update: Kepler discoveries the talk of the town |author=Rich Talcott |date=5 January 2010 |work=Astronomy.com |publisher=[[Astronomy (magazine)|Astronomy]] magazine |access-date=11 March 2011 |archive-date=18 July 2011 |archive-url=https://web.archive.org/web/20110718093334/http://cs.astronomy.com/asycs/blogs/astronomy/archive/2010/01/05/215th-aas-meeting-update-kepler-discoveries-the-talk-of-the-town.aspx |url-status=dead }}</ref>

==Host star== {{main|Kepler-4}} [[Kepler-4]] is a star very similar to the sun<ref name="Borucki2010"/> located about 1610 light-years away<ref name="Gaia DR2"/> from Earth, in the [[constellation]] of [[Draco (constellation)|Draco]].<ref name="Roman1987"/>

==Characteristics== Kepler-4b orbits its host star in 3.213 days at a distance of 0.046 [[astronomical unit|AU]].<ref name="Borucki2010"/> This places it almost 10 times closer to its star than Mercury is to the Sun. Consequently, Kepler-4b is thought to be extremely hot, with an [[equilibrium temperature]] greater than 1700 [[kelvin]]s (2600 °F). (1426°C)<ref name="Kipping2010"/> The planet is estimated to be 25 times more massive than the Earth with a radius that is 4 times greater than the Earth.<ref name="Borucki2010"/> This makes it similar to Neptune in terms of size and mass, but with a temperature that is not comparable to any planet in the Solar System (Venus, the hottest planet, is only 735 kelvins). Kepler-4b's [[orbital eccentricity|eccentricity]] was assumed to be 0, however an independent reanalysis of the discovery data found a value of 0.25 ± 0.12,<ref name="Kipping2010"/> and a later reanalysis of the light curve discovered a secondary eclipse with depth 7.47 ± 1.82ppm at a phase of about 0.7.<ref name="Sheets2017"/>

[[File:Kepler first five exoplanet size.jpg|thumb|300px|A picture showing the relative sizes of the first five planets discovered by Kepler. Kepler-4b is the smallest of the five, highlighted in purple.]]

==See also== * [[List of exoplanets discovered by the Kepler space telescope]]

==References== <references> <ref name="Borucki2010">{{cite journal | title=Kepler-4b: A Hot Neptune-like Planet of a G0 Star Near Main-sequence Turnoff | last1=Borucki | first1=William J. | last2=Koch | first2=David G. | last3=Brown | first3=Timothy M. | last4=Basri | first4=Gibor | last5=Batalha | first5=Natalie M. | last6=Caldwell | first6=Douglas A. | last7=Cochran | first7=William D. | last8=Dunham | first8=Edward W. | last9=Gautier III | first9=Thomas N. | display-authors=1 | journal=The Astrophysical Journal Letters | volume=713 | issue=2 | pages=L126–L130 | year=2010 | arxiv=1001.0604 | bibcode=2010ApJ...713L.126B | bibcode-access=free | doi=10.1088/2041-8205/713/2/L126 | doi-access=free }}</ref>

<ref name="Borucki2011">{{cite journal | title=Characteristics of Planetary Candidates Observed by Kepler. II. Analysis of the First Four Months of Data | last1=Borucki | first1=William J. | last2=Koch | first2=David G. | last3=Basri | first3=Gibor | last4=Batalha | first4=Natalie | last5=Brown | first5=Timothy M. | last6=Bryson | first6=Stephen T. | last7=Caldwell | first7=Douglas | last8=Christensen-Dalsgaard | first8=Jørgen | last9=Cochran | first9=William D. | last10=Devore | first10=Edna | last11=Dunham | first11=Edward W. | last12=Gautier | first12=Thomas N. | last13=Geary | first13=John C. | last14=Gilliland | first14=Ronald | last15=Gould | first15=Alan | last16=Howell | first16=Steve B. | last17=Jenkins | first17=Jon M. | last18=Latham | first18=David W. | last19=Lissauer | first19=Jack J | last20=Marcy | first20=Geoffrey W. | last21=Rowe | first21=Jason | last22=Sasselov | first22=Dimitar | last23=Boss | first23=Alan | last24=Charbonneau | first24=David | last25=Ciardi | first25=David | last26=Doyle | first26=Laurance | last27=Dupree | first27=Andrea K. | last28=Ford | first28=Eric B. | last29=Fortney | first29=Jonathan | last30=Holman | first30=Matthew J. | display-authors=1 | journal=The Astrophysical Journal | volume=736 | issue=1 | at=19 | year=2011 | arxiv=1102.0541 | bibcode=2011ApJ...736...19B | bibcode-access=free | doi=10.1088/0004-637X/736/1/19 | doi-access=free }}</ref>

<ref name="datatable">{{cite web |url=http://kepler.nasa.gov/Mission/discoveries/ |archive-url=https://web.archive.org/web/20100527104316/http://kepler.nasa.gov/Mission/discoveries/ |url-status=dead |archive-date=2010-05-27 |title=Summary Table of Kepler Discoveries |date=2010-03-15 |publisher=NASA|access-date=2010-03-18}}</ref>

<ref name="Kipping2010">{{cite journal | title=An Independent Analysis of Kepler-4b through Kepler-8b | last1=Kipping | first1=David | last2=Bakos | first2=Gáspár | journal=The Astrophysical Journal | date=2011 | volume=730 | issue=1 | at=50 | arxiv=1004.3538 | bibcode=2011ApJ...730...50K | bibcode-access=free | doi=10.1088/0004-637X/730/1/50 | doi-access=free }}</ref>

<ref name="Mission overview">{{cite web | title=Mission overview | url=https://www.nasa.gov/mission_pages/kepler/overview/index.html | work=Kepler and K2 | date=13 April 2015 | publisher=NASA | access-date=3 December 2017}}</ref>

<ref name="Roman1987">{{cite journal | title=Identification of a Constellation From a Position | last1=Roman | first1=Nancy G. | journal=Publications of the Astronomical Society of the Pacific | volume=99 | issue=617 | pages=695–699 | year=1987 | bibcode=1987PASP...99..695R | bibcode-access=free | doi=10.1086/132034 | doi-access=free }} [http://vizier.u-strasbg.fr/vizier/VizieR/constellations.htx Vizier query form ]</ref>

<ref name="sciencenews">{{cite web |url=https://www.usnews.com/science/articles/2010/01/04/space-telescope-finds-its-first-extrasolar-planets |title=Kepler space telescope finds its first extrasolar planets |author=Ron Cowen |date=2010-01-04 |publisher=Science News|access-date=2010-01-04}}</ref>

<ref name="Sheets2017">{{cite journal | title=Average Albedos of Close-in Super-Earths and Super-Neptunes from Statistical Analysis of Long-cadence Kepler Secondary Eclipse Data | last1=Sheets | first1=Holly A. | last2=Deming | first2=Drake | journal=The Astronomical Journal | volume=154 | issue=4 | at=160 | year=2017 | arxiv=1708.08459 | bibcode=2017AJ....154..160S | bibcode-access=free | doi=10.3847/1538-3881/aa88b9 | doi-access=free }}</ref> </references>

==External links== {{commonscat-inline|Kepler-4 b}} *[https://web.archive.org/web/20100527185701/http://kepler.nasa.gov/Mission/discoveries/kepler4b/ NASA.gov]

{{DEFAULTSORT:Kepler-4b}} [[Category:Exoplanets with Kepler designations]] [[Category:Exoplanets discovered in 2010]] [[Category:Hot Neptunes|Kepler-04b]] [[Category:Giant planets]] [[Category:Transiting exoplanets]] [[Category:Draco (constellation)]] [[Category:Exoplanets discovered by the Kepler space telescope|4b]]