Kepler-4

Kepler-4 is a sunlike star located about 1610 light-years away in the constellation Draco. It is in the field of view of the Kepler Mission, a NASA operation purposed with finding Earth-like planets. Kepler-4b, a Neptune-sized planet that orbits extremely close to its star, was discovered in its orbit and made public by the Kepler team on January 4, 2010. Kepler-4b was the first discovery by the Kepler satellite, and its confirmation helped to demonstrate the spacecraft's effectiveness.

Kepler-4
Observation data
Epoch J2000      Equinox J2000
Constellation Draco[1]
Right ascension 19h 2m 27.6981s[2]
Declination +50° 8′ 08.704″[2]
Apparent magnitude (V) 12.7[3]
Characteristics
Spectral type G0[4]
Astrometry
Proper motion (μ) RA: 6.003±0.039[2] mas/yr
Dec.: 4.672±0.043[2] mas/yr
Parallax (π)2.0209 ± 0.0243[2] mas
Distance1,610 ± 20 ly
(495 ± 6 pc)
Details
Mass1.117+0.021
−0.029[5] M☉
Radius1.555±0.012[5] R☉
Luminosity2.505+0.142
−0.124[5] L☉
Surface gravity (log g)4.102+0.005
−0.004[5] cgs
Temperature5781±76[6] K
Metallicity [Fe/H]0.09±0.10[6] dex
Age6.71+0.77
−0.67[5] Gyr
Other designations
KOI-7, KIC 11853905, GSC 03549-02067, 2MASS J19022767+5008087[7]
Database references
SIMBADdata
KICdata

Nomenclature and history

Kepler-4 is named for the Kepler spacecraft, a NASA telescope tasked with finding Earth-like planets that transit their stars as seen from Earth.[8] As the previous three planets that Kepler confirmed had already been confirmed by others, Kepler-4 and its planet were the first to be discovered by the Kepler team.[9] The star and its system were announced in Washington, D.C. at the 215th meeting of the American Astronomical Society on January 4, 2010, along with Kepler-5, Kepler-6, Kepler-7, and Kepler-8. Of the presented planets, Kepler-4b was the smallest, around the size of planet Neptune.[10] The discovery of Kepler-4b and the other planets presented at the AAS meeting helped to confirm that the Kepler spacecraft was indeed functional.[11]

The Harlan J. Smith Telescope at McDonald Observatory in Fort Davis, Texas was used by astronomers from the University of Texas at Austin to follow up on Kepler's discoveries and confirm them.[12] Telescopes in Hawaii, California, Arizona, and the Canary Islands were also used to confirm the findings.[11]

Characteristics
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.

Kepler-4 is a G0-type star, which is similar to the Sun, except slightly brighter. The star is 1.117 Msun and 1.555 Rsun, or 111% the mass of and 155% the radius of the Sun.[5] With a metallicity of .09 (± 0.10) [Fe/H], Kepler-4 is more metal-rich than the Sun, a figure that is important in that metal-rich stars tend to have orbiting planets more often than metal-poor stars. Kepler-4 is also about 6.7 billion years old.[5] In comparison, the Sun is 4.6 billion years old.[13] In addition, Kepler-4 has an effective temperature of 5781 (± 76) K,[6] which is almost identical, within the errors, to that of the Sun, which is 5778 K.[14]

As seen from Earth, Kepler-4 has an apparent magnitude of 12.7. It is, as a result, not visible with the naked eye.[3]

Planetary system

Kepler-4b's discovery was announced on January 4, 2010. It is the size of planet Neptune, at 0.077 MJ (7% the mass of Jupiter) and 0.357 RJ (36% the radius of Jupiter). The planet orbits its star every 3.213 days at 0.045 AU from the star.[4] This distance compares to planet Mercury, which is 0.39 AU from the Sun.[15] Kepler-4's eccentricity was assumed to be 0, however a subsequent independent reanalysis of the discovery data found a value of 0.25 ± 0.12.[16] Likewise, the temperature of the planet is assumed to be 1650 K, far hotter than Jupiter's, which is assumed to be 124 K (not considering its internal heat and atmosphere).[4]

A search for transit-timing variations in all 17 quarters of Kepler data did not detect any evidence of additional planets.[17]

The Kepler-4 planetary system[4][16]
Companion
(in order from star)		 Mass Semimajor axis
(AU)		 Orbital period
(days)		 Eccentricity Inclination Radius
b 0.077±0.012 MJ 0.0456±0.0009 3.21346±0.00022 0.25±0.12 89.76+0.24
−2.05°		 0.357±0.019 RJ
Kepler-4 System.

See also

References
  1. Roman, Nancy G. (1987). "Identification of a Constellation From a Position". Publications of the Astronomical Society of the Pacific. 99 (617): 695–699. Bibcode:1987PASP...99..695R. doi:10.1086/132034. Vizier query form
  2. Brown, A. G. A.; et al. (Gaia collaboration) (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics. 616. A1. arXiv:1804.09365. Bibcode:2018A&A...616A...1G. doi:10.1051/0004-6361/201833051. Gaia DR2 record for this source at VizieR.
  3. Jean Schneider (2010). "Planet Kepler-4 b". Extrasolar Planets Encyclopaedia. Jean Schneider. Retrieved 5 August 2012.
  4. Borucki, William J.; et al. (2010). "Kepler-4b: A Hot Neptune-like Planet of a G0 Star Near Main-sequence Turnoff". The Astrophysical Journal Letters. 713 (2): L126–L130. arXiv:1001.0604. Bibcode:2010ApJ...713L.126B. doi:10.1088/2041-8205/713/2/L126.
  5. Silva Aguirre, V.; et al. (2015). "Ages and fundamental properties of Kepler exoplanet host stars from asteroseismology". Monthly Notices of the Royal Astronomical Society. 452 (2): 2127–2148. arXiv:1504.07992. Bibcode:2015MNRAS.452.2127S. doi:10.1093/mnras/stv1388.
  6. Huber, Daniel; et al. (2013). "Fundamental Properties of Kepler Planet-candidate Host Stars using Asteroseismology". The Astrophysical Journal. 767 (2). 127. arXiv:1302.2624. Bibcode:2013ApJ...767..127H. doi:10.1088/0004-637X/767/2/127.
  7. "Kepler-4". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2018-06-03.
  8. "Mission overview". Kepler and K2. NASA. Retrieved 2 December 2017.
  9. "Summary Table of Kepler Discoveries". NASA. 2010-08-27. Retrieved 2010-10-16.
  10. Rich Talcott (5 January 2010). "215th AAS meeting update: Kepler discoveries the talk of the town". Astronomy.com. Astronomy magazine. Retrieved 24 February 2011.
  11. "NASA's Kepler Space Telescope Discovers its First Five Exoplanets". NASA. 4 January 2010. Retrieved 25 February 2011.
  12. "Texas Astronomers Aid Kepler Mission's Discovery of New Planets". UT News. University of Texas at Austin. 4 January 2010. Retrieved 7 August 2020.
  13. Fraser Cain (16 September 2008). "How Old is the Sun?". Universe Today. Retrieved 25 February 2011.
  14. David Williams (1 September 2004). "Sun Fact Sheet". Goddard Space Flight Center. NASA. Retrieved 25 February 2011.
  15. David Williams (17 November 2010). "Mercury Fact Sheet". Goddard Space Flight Center. NASA. Retrieved 25 February 2011.
  16. Kipping, David; Bakos, Gáspár (2011). "An Independent Analysis of Kepler-4b through Kepler-8b". The Astrophysical Journal. 730 (1). 50. arXiv:1004.3538. Bibcode:2011ApJ...730...50K. doi:10.1088/0004-637X/730/1/50.
  17. Gajdoš, Pavol; Vaňko, Martin; Parimucha, Štefan (2019). "Transit timing variations and linear ephemerides of confirmed Kepler transiting exoplanets". Research in Astronomy and Astrophysics. 19 (3). 041. arXiv:1809.11104. Bibcode:2019RAA....19...41G. doi:10.1088/1674-4527/19/3/41.Vizier catalog entry

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