Kepler-4

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Kepler-4
Observation data
Epoch J2000      Equinox J2000
Constellation Draco
Right ascension 19h 2m 27.68s[1]
Declination +50° 8′ 8.7″[1]
Apparent magnitude (V) 12.6
Astrometry
Distance 1631 ly
(550 pc)
Characteristics
Spectral type G0
Details
Mass 1.223 M
Radius 1.487 R
Luminosity 0.354±0.1 L
Temperature 5857 K
Age 4.5 Gyr
Other designations
KIC 11853905, KOI 7, 2MASS 19022767+5008087

Kepler-4 is a sunlike star located about 1631 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.

Nomenclature and history[edit]

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.[2] As the previous three planets that Kepler confirmed had already been confirmed by other finds, Kepler-4 and its planet were the first to be discovered by the Kepler team.[3] 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.[4] The discovery of Kepler-4b and the other planets presented at the AAS meeting helped to confirm that the Kepler spacecraft was indeed functional.[5]

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.[6] Telescopes in Hawaii, California, Arizona, and the Canary Islands were also used to confirm the findings.[5]

Characteristics[edit]

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 1.223 Msun and 1.487 Rsun, or 122% the mass of and 148% the radius of the Sun. With a metallicity of .17 (± 0.06) [Fe/H], Kepler-4 is more metal-rich than the Sun by 48%, 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 4.5 (± 1.5) billion years old.[7] In comparison, the Sun is 4.6 billion years old.[8] In addition, Kepler-4 has an effective temperature of 5857 (± 120) K, compared to that of the Sun, which is 5778 K.[9]

As seen from Earth, Kepler-4 has an apparent magnitude of 12.7. It is, as a result, not visible with the naked eye.[7]

Planetary system[edit]

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 3.214 days at 0.045 AU from the star.[3] This distance compares to planet Mercury, which is 0.39 AU from the Sun.[10] 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.[11] 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).[3]

The Kepler-4 planetary system[3][11]
Companion
(in order from star)
Mass Semimajor axis
(AU)
Orbital period
(days)
Eccentricity Inclination Radius
b 0.077 MJ 0.04558 3.2135 0.25 ± 0.12 89.76° 0.357 RJ

See also[edit]

References[edit]

  1. ^ a b 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. arXiv:1001.0604. Bibcode:2010ApJ...713L.126B. doi:10.1088/2041-8205/713/2/L126. 
  2. ^ "Kepler: About the Mission". Kepler Mission. NASA. 2011. Retrieved 24 February 2011. 
  3. ^ a b c d "Summary Table of Kepler Discoveries". NASA. 2010-08-27. Retrieved 2010-10-16. 
  4. ^ Rich Talcott (5 January 2010). "215th AAS meeting update: Kepler discoveries the talk of the town". Astronomy.com. Astronomy magazine. Retrieved 24 February 2011. 
  5. ^ a b "NASA's Kepler Space Telescope Discovers its FIrst Five Exoplanets". NASA. 4 January 2010. Retrieved 25 February 2011. 
  6. ^ "Texas Astronomers Aid Kepler Mission's Discovery of New Planets". UT News. University of Texas at Austin. 4 January 2010. Retrieved 25 February 2011. 
  7. ^ a b Jean Schneider (2010). "Planet Kepler-4 b". Extrasolar Planets Encyclopaedia. Jean Schneider. Retrieved 5 August 2012. 
  8. ^ Fraser Cain (16 September 2008). "How Old is the Sun?". Universe Today. Retrieved 25 February 2011. 
  9. ^ David Williams (1 September 2004). "Sun Fact Sheet". Goddard Space Flight Center. NASA. Retrieved 25 February 2011. 
  10. ^ David Williams (17 November 2010). "Mercury Fact Sheet". Goddard Space Flight Center. NASA. Retrieved 25 February 2011. 
  11. ^ a b 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. 

Coordinates: Sky map 19h 2m 27.7s, +50° 8′ 8.7″