# Kepler-4b

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Extrasolar planet in the constellation Draco

Kepler-4b Size comparison of Neptune (left) with Kepler-4b (right). Discovery[1] Discovery date 2010-01-04[2] Detection method Transit (Kepler Mission)[3] Orbital characteristics Semi-major axis 0.04558 AU (6,819,000 km)[4] Eccentricity 0.25 ± 0.12[5] Orbital period (sidereal) 3.2135[4] d Inclination 89.76[4] Star Kepler-4[4] Physical characteristics Mean radius 0.357[4] RJ Mass 0.077[4] MJ Temperature 1650 k[4]

**Kepler-4b**, initially known as **KOI 7.01**, is an [extrasolar planet](/source/Exoplanet) first detected as a [transit](/source/Astronomical_transit) by the [Kepler spacecraft](/source/Kepler_(spacecraft)). Its [radius](/source/Radius) and [mass](/source/Mass) are similar to that of [Neptune](/source/Neptune); however, due to its proximity to its host star, it is substantially hotter than any planet in the Solar System.[4][6] The planet's discovery was announced on January 4, 2010, in [Washington, D.C.](/source/Washington%2C_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](/source/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](/source/Kepler-4). The star was, in turn, named for the Kepler Mission, a [NASA](/source/NASA) satellite whose purpose is to discover Earth-like planets in a section of the sky between constellations [Cygnus](/source/Cygnus_(constellation)) and [Lyra](/source/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.[3] Initially, Kepler-4b was detected as a transit event by the [Kepler telescope](/source/Kepler_telescope) and considered a [Kepler Object of Interest](/source/Kepler_Object_of_Interest) with the designation KOI 7.01.[7]

Subsequent [radial velocity](/source/Radial_velocity) measurements by the [High Resolution Echelle Spectrometer](/source/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.[1] The planet's discovery was announced on January 4, 2010, along with four other planets detected by Kepler: [Kepler-5b](/source/Kepler-5b), [6b](/source/Kepler-6b), [7b](/source/Kepler-7b) and [8b](/source/Kepler-8b)[6] at the 215th meeting of the [American Astronomical Society](/source/American_Astronomical_Society) in Washington, D.C.[2]

## Host star

Main article: [Kepler-4](/source/Kepler-4)

[Kepler-4](/source/Kepler-4) is a star very similar to the sun[1] located about 1610 light-years away[8] from Earth, in the [constellation](/source/Constellation) of [Draco](/source/Draco_(constellation)).[9]

## Characteristics

Kepler-4b orbits its host star in 3.213 days at a distance of 0.046 [AU](/source/Astronomical_unit).[1] 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](/source/Equilibrium_temperature) greater than 1700 [kelvins](/source/Kelvin) (2600 °F). (1426°C)[5] The planet is estimated to be 25 times more massive than the Earth with a radius that is 4 times greater than the Earth.[1] 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 [eccentricity](/source/Orbital_eccentricity) was assumed to be 0, however an independent reanalysis of the discovery data found a value of 0.25 ± 0.12,[5] 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.[10]

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](/source/List_of_exoplanets_discovered_by_the_Kepler_space_telescope)

## References

1. ^ [***a***](#cite_ref-Borucki2010_1-0) [***b***](#cite_ref-Borucki2010_1-1) [***c***](#cite_ref-Borucki2010_1-2) [***d***](#cite_ref-Borucki2010_1-3) [***e***](#cite_ref-Borucki2010_1-4) Borucki, William J.; et al. (2010). ["Kepler-4b: A Hot Neptune-like Planet of a G0 Star Near Main-sequence Turnoff"](https://doi.org/10.1088%2F2041-8205%2F713%2F2%2FL126). *The Astrophysical Journal Letters*. **713** (2): L126–L130. [arXiv](/source/ArXiv_(identifier)):[1001.0604](https://arxiv.org/abs/1001.0604). [Bibcode](/source/Bibcode_(identifier)):[2010ApJ...713L.126B](https://ui.adsabs.harvard.edu/abs/2010ApJ...713L.126B). [doi](/source/Doi_(identifier)):[10.1088/2041-8205/713/2/L126](https://doi.org/10.1088%2F2041-8205%2F713%2F2%2FL126).

1. ^ [***a***](#cite_ref-Talcott_2-0) [***b***](#cite_ref-Talcott_2-1) Rich Talcott (5 January 2010). ["215th AAS meeting update: Kepler discoveries the talk of the town"](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). *Astronomy.com*. [Astronomy](/source/Astronomy_(magazine)) magazine. Archived from [the original](http://cs.astronomy.com/asycs/blogs/astronomy/archive/2010/01/05/215th-aas-meeting-update-kepler-discoveries-the-talk-of-the-town.aspx) on 18 July 2011. Retrieved 11 March 2011.

1. ^ [***a***](#cite_ref-Mission_overview_3-0) [***b***](#cite_ref-Mission_overview_3-1) ["Mission overview"](https://www.nasa.gov/mission_pages/kepler/overview/index.html). *Kepler and K2*. NASA. 13 April 2015. Retrieved 3 December 2017.

1. ^ [***a***](#cite_ref-datatable_4-0) [***b***](#cite_ref-datatable_4-1) [***c***](#cite_ref-datatable_4-2) [***d***](#cite_ref-datatable_4-3) [***e***](#cite_ref-datatable_4-4) [***f***](#cite_ref-datatable_4-5) [***g***](#cite_ref-datatable_4-6) [***h***](#cite_ref-datatable_4-7) ["Summary Table of Kepler Discoveries"](https://web.archive.org/web/20100527104316/http://kepler.nasa.gov/Mission/discoveries/). NASA. 2010-03-15. Archived from [the original](https://kepler.nasa.gov/Mission/discoveries/) on 2010-05-27. Retrieved 2010-03-18.

1. ^ [***a***](#cite_ref-Kipping2010_5-0) [***b***](#cite_ref-Kipping2010_5-1) [***c***](#cite_ref-Kipping2010_5-2) Kipping, David; Bakos, Gáspár (2011). ["An Independent Analysis of Kepler-4b through Kepler-8b"](https://doi.org/10.1088%2F0004-637X%2F730%2F1%2F50). *The Astrophysical Journal*. **730** (1). 50. [arXiv](/source/ArXiv_(identifier)):[1004.3538](https://arxiv.org/abs/1004.3538). [Bibcode](/source/Bibcode_(identifier)):[2011ApJ...730...50K](https://ui.adsabs.harvard.edu/abs/2011ApJ...730...50K). [doi](/source/Doi_(identifier)):[10.1088/0004-637X/730/1/50](https://doi.org/10.1088%2F0004-637X%2F730%2F1%2F50).

1. ^ [***a***](#cite_ref-sciencenews_6-0) [***b***](#cite_ref-sciencenews_6-1) Ron Cowen (2010-01-04). ["Kepler space telescope finds its first extrasolar planets"](https://www.usnews.com/science/articles/2010/01/04/space-telescope-finds-its-first-extrasolar-planets). Science News. Retrieved 2010-01-04.

1. **[^](#cite_ref-Borucki2011_7-0)** Borucki, William J.; et al. (2011). ["Characteristics of Planetary Candidates Observed by Kepler. II. Analysis of the First Four Months of Data"](https://doi.org/10.1088%2F0004-637X%2F736%2F1%2F19). *The Astrophysical Journal*. **736** (1). 19. [arXiv](/source/ArXiv_(identifier)):[1102.0541](https://arxiv.org/abs/1102.0541). [Bibcode](/source/Bibcode_(identifier)):[2011ApJ...736...19B](https://ui.adsabs.harvard.edu/abs/2011ApJ...736...19B). [doi](/source/Doi_(identifier)):[10.1088/0004-637X/736/1/19](https://doi.org/10.1088%2F0004-637X%2F736%2F1%2F19).

1. **[^](#cite_ref-Gaia_DR2_8-0)** [Brown, A. G. A.](/source/Anthony_Brown_(scientist)); et al. ([Gaia collaboration](/source/Data_Processing_and_Analysis_Consortium)) (August 2018). ["*Gaia* Data Release 2: Summary of the contents and survey properties"](https://doi.org/10.1051%2F0004-6361%2F201833051). *[Astronomy & Astrophysics](/source/Astronomy_%26_Astrophysics)*. **616**. A1. [arXiv](/source/ArXiv_(identifier)):[1804.09365](https://arxiv.org/abs/1804.09365). [Bibcode](/source/Bibcode_(identifier)):[2018A&A...616A...1G](https://ui.adsabs.harvard.edu/abs/2018A&A...616A...1G). [doi](/source/Doi_(identifier)):[10.1051/0004-6361/201833051](https://doi.org/10.1051%2F0004-6361%2F201833051). [Gaia DR2 record for this source](https://vizier.u-strasbg.fr/viz-bin/VizieR-S?Gaia%20DR2%202132152916856093952) at [VizieR](/source/VizieR).

1. **[^](#cite_ref-Roman1987_9-0)** Roman, Nancy G. (1987). ["Identification of a Constellation From a Position"](https://doi.org/10.1086%2F132034). *Publications of the Astronomical Society of the Pacific*. **99** (617): 695–699. [Bibcode](/source/Bibcode_(identifier)):[1987PASP...99..695R](https://ui.adsabs.harvard.edu/abs/1987PASP...99..695R). [doi](/source/Doi_(identifier)):[10.1086/132034](https://doi.org/10.1086%2F132034). [Vizier query form](http://vizier.u-strasbg.fr/vizier/VizieR/constellations.htx)

1. **[^](#cite_ref-Sheets2017_10-0)** Sheets, Holly A.; Deming, Drake (2017). ["Average Albedos of Close-in Super-Earths and Super-Neptunes from Statistical Analysis of Long-cadence Kepler Secondary Eclipse Data"](https://doi.org/10.3847%2F1538-3881%2Faa88b9). *The Astronomical Journal*. **154** (4). 160. [arXiv](/source/ArXiv_(identifier)):[1708.08459](https://arxiv.org/abs/1708.08459). [Bibcode](/source/Bibcode_(identifier)):[2017AJ....154..160S](https://ui.adsabs.harvard.edu/abs/2017AJ....154..160S). [doi](/source/Doi_(identifier)):[10.3847/1538-3881/aa88b9](https://doi.org/10.3847%2F1538-3881%2Faa88b9).

## External links

Media related to [Kepler-4 b](https://commons.wikimedia.org/wiki/Category:Kepler-4_b) at Wikimedia Commons

- [NASA.gov](https://web.archive.org/web/20100527185701/http://kepler.nasa.gov/Mission/discoveries/kepler4b/)

v t e Constellation of Draco List of stars in Draco Draco in Chinese astronomy Stars Bayer α (Thuban) β (Rastaban) γ (Eltanin) δ (Altais) ε (Tyl) ζ (Aldhibah) η (Athebyne) θ ι (Edasich) κ λ (Giausar) μ (Alrakis) ν (Kuma) ξ (Grumium) ο π ρ σ (Alsafi) τ υ φ χ ψ1 (Dziban) ψ2 ω Flamsteed 4 6 7 (Tianyi) 8 (Taiyi) 10 (i) 15 (A) 18 (g) 19 (h) 26 36 39 (b) 42 (Fafnir) 45 (d) 50 59 64 (e) 68 Variable TW YY AG BY CL CM CX DO EK HP V581 HR 3751 4126 4934 5811 6237 6518 6618 (Alruba) 6817 7137 7783 HD 109246 (Funi) 101364 128717 147379 156279 158259 176693 191939 Other 2MASS 1237+6526 2MASS J17554042+6551277 G 240-72 GD 356 Gliese 420 Gliese 625 Gliese 687 GRW +70 8247 Kepler-4 Kepler-10 Kepler-12 Kepler-90 Kepler-296 KOI-256 LP 71-82 Qatar-1 SDSS J1240+6710 Struve 2398 TOI-1136 WD 1856+534 WISE 1647+5632 WISE 1841+7000 Exoplanets HD 139357 b HD 167042 b ι Dra b (Hypatia) Kepler-4b Kepler-10b c Kepler-12b Kepler-90e f g h i Kepler-296b c d e f TOI-1452 b TrES-2b Star clusters LAMOST 1 Nebulae Cat's Eye Nebula NGC 6742 Galaxies NGC 3147 3197 3735 4121 4125 4221 4236 4319 4331 4332 4363 4441 4513 4545 4589 5678 5777 5866 5866B 5879 5905 5907 5949 5963 5965 5982 5985 6090 6248 6285 6286 6338 6340 6365 6373 6394 6412 6503 6505 6566 6621 6622 6670 6676 6786 6789 Other 1ES 1927+654 1ES 1959+650 3C 249.1 3C 305 3C 319 3C 343 3C 343.1 3C 351 3C 356 3C 371 3C 380 3C 390.3 3C 401 4C +72.26 4C 73.08 8C 1241+735 Abell 2218 BCG Bean galaxy Beaver galaxy BZQ J1727+5510 Draco Dwarf Draco II GB 1508+5714 Goldfish galaxy H1821+643 HFLS3 IERS B1946+708 IRAS F17179+5444 IRAS 18580+6527 J120011.1+680924.8 KKR 25 Markarian 817 Markarian 876 Original TRG PGC 39058 Porphyrion QSO B1823+568 RGZ J172749.5+534647 S5 1803+784 S5 2007+777 SDSS J1715+6008 Tadpole Galaxy UGC 9391 UGC 9405 UGC 11241 UGC 11411 WISEA J145223.62+611707.5 WN B1851+5707 Galaxy clusters Abell 2218 CL1358+62 Draco Supercluster NGC 5866 Group Astronomical events SN 2003jb SN 2005B SN 2016aps Swift J1644+57 Category

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Adapted from the Wikipedia article [Kepler-4b](https://en.wikipedia.org/wiki/Kepler-4b) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/Kepler-4b?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.