PH1b

PH1 ^[1]

Extrasolar planet		List of extrasolar planets
Artist's concept of a quadruple-star system, similar to one found to contain the extrasolar planet PH1. credit: NASA/JPL-Caltech/T. Pyle (SSC).
Parent star
Star		Kepler 64 OR KIC 4862625's A-component ( KIC 4862625 A or KIC 4862625 Aa+Ab or KIC 4862625 Aab ) [1][2]
Constellation		Cygnus
Right ascension	(α)	19h 52m 51.624s [2]
Declination	(δ)	+39° 57′ 18.36″ [2]
Distance		5000 [3] ly (1500 pc)
Spectral type		F + M [2]
Mass	(m)	1.528±0.087 + 0.408±0.024 [3][4] M☉
Radius	(r)	1.734±0.044 + 0.378±0.023 [4] R☉
Metallicity	[Fe/H]	+0.21±0.08 [2]
Age		9 Gyr
Orbital elements
Semimajor axis	(a)	0.634 ± 0.011 [2] AU
Orbital period	(P)	138.506+0.107 −0.092 [2] d
Semi-amplitude	(K)	20.69 ± 0.31 ×103 [2] m/s
Physical characteristics
Mass	(m)	0.08-0.14 [2] MJ (20-50 [2] M⊕)
Maximum mass	(m sin i)	0.531 [2] MJ (169 [2] M⊕)
Radius	(r)	6.18 ± 0.17 [2] R⊕
Temperature	(T)	524-613 [2] K
Discovery information
Discovery date		15 October 2012 [5]
Discoverer(s)		Planet Hunters
Discovery method		Transit [5]
Other detection methods		Transit duration variations
Discovery site		Kepler space telescope
Discovery status		Published

PH1b (standing for "Planet Hunters 1"), or by its NASA designation Kepler-64b,^[6] is an extrasolar planet found in a circumbinary orbit in the quadruple star system Kepler-64. The planet was discovered by two amateur astronomers from the Planet Hunters project of amateur astronomers using data from the Kepler space telescope with assistance of a Yale University team of international astronomers. The discovery was announced on October 15, 2012.^[7][8] It is the first known transiting planet in a quadruple star system,^[4] first known circumbinary planet in a quadruple star system,^[9] and the first planet in a quadruple star system found. It was the first confirmed planet discovered by PlanetHunters.org.^[5]

Discovery

Light curve signaling the discovery of PH1, showing the first 3 transits of Kepler-64 (KIC 4862625)

Kian Jek, from San Francisco, and Robert Gagliano, from Cottonwood, Arizona, spotted the signature of the planet in the Kepler data, and it was reported through the PlanetHunters.org program run by Dr. Chris Lintott, from Oxford University.^[8] Kian Jek first spotted a light dip indicative of a transit in May 2011. JKD reported a second. Robert Gagliano performed a systematic search, and confirmed the second dip, and found a third, in February 2012. Using this, Kian predicted another transit, and found it. The planet was subsequently detected by eclipsing binary timing variation method.^[1] At the time of discovery, it was the sixth known circumbinary planet.

Star system

The giant planet is Neptune-sized, about 20-55 Earth-masses. It has a radius 6.2 times that of Earth's. The star system is 5000 light years from Earth.^{[2][3][8][10]} The planet orbits a close binary, with a more distant binary orbitting at a distance, forming the quadruple star system. The star system has the Kepler Input Catalogue name KIC 4862625 as well as the designation Kepler-64. The close binary (Aa+Ab) that the planet circles has an orbital period of 20 days. They form an eclipsing binary pair.^[1] The two stars are (Aa) 1.5 solar mass F-type dwarf and (Ab) 0.41 solar mass M-type dwarf.^[2][3][4] The planet orbits this binary pair in a 138.3-day orbit. The binary pairs has a separation of 1000 AUs.^[1] A photometric-dynamical model was used to model the planetary system of the close binary pair. The distant binary (Ba+Bb) have a pair separation of 60 AU. The two stars are (Ba) 0.99 solar mass G-type dwarf and (Bb) 0.51 solar mass M-type dwarf. The quadruple star system has an estimated age of 2 gigayears.^[2] The system is located at right ascension 19^h 52^m 51.624^s declination +39° 57′ 18.36″, so also has a 2MASS catalogue entry of 2MASS 19525162+3957183^[11]

References

Further reading

• Discovery Announcement: PlanetHunters.org, "PH1 : A planet in a four-star system", 15 October 2012 (accessed 20 October 2012)
• Discovery Paper: arXiv. "Planet Hunters: A Transiting Circumbinary Planet in a Quadruple Star System", Megan E. Schwamb, Jerome A. Orosz, Joshua A. Carter, William F. Welsh, Debra A. Fischer, Guillermo Torres, Andrew W. Howard, Justin R. Crepp, William C. Keel, Chris J. Lintott, Nathan A. Kaib, Dirk Terrell, Robert Gagliano, Kian J. Jek, Michael Parrish, Arfon M. Smith, Stuart Lynn, Robert J. Simpson, Matthew J. Giguere, Kevin Schawinski, 2012 October, arXiv:1210.3612 ; Bibcode: 2012arXiv1210.3612S ;

External links

• NASA JPL, "Citizens Discover Four-Star Planet with NASA's Kepler", Whitney Clavin, 15 October 2012 (accessed 20 October 2012)

See also

• List of extrasolar planet firsts
• PH2 b