PH1b (standing for "Planet Hunters 1"), or by its NASA designation Kepler-64b, is an

extrasolar planet An exoplanet or extrasolar planet is a planet outside the Solar System. The first confirmed detection of an exoplanet was in 1992 around a pulsar, and the first detection around a main-sequence star was in 1995. A different planet, first detect ...

found in a circumbinary orbit in the quadruple star system Kepler-64. The planet was discovered by two amateur astronomers from the

Planet Hunters Planet Hunters is a citizen science project to find exoplanets using human eyes. It does this by having users analyze data from the NASA Kepler space telescope and the NASA Transiting Exoplanet Survey Satellite. It was launched by a team led by D ...

project of

amateur astronomer Amateur astronomy is a hobby where participants enjoy observing or imaging celestial objects in the sky using the unaided eye, binoculars, or telescopes. Even though scientific research may not be their primary goal, some amateur astronomers m ...

s using data from the

Kepler space telescope The Kepler space telescope is a defunct space telescope launched by NASA in 2009 to discover Earth-sized planets orbiting other stars. Named after astronomer Johannes Kepler, the spacecraft was launched into an Earth-trailing heliocentric orb ...

with assistance of a

Yale University Yale University is a Private university, private Ivy League research university in New Haven, Connecticut, United States. Founded in 1701, Yale is the List of Colonial Colleges, third-oldest institution of higher education in the United Stat ...

team of international

astronomer An astronomer is a scientist in the field of astronomy who focuses on a specific question or field outside the scope of Earth. Astronomers observe astronomical objects, such as stars, planets, natural satellite, moons, comets and galaxy, galax ...

s. The discovery was announced on 15 October 2012. It is the first known

transiting planet In astronomy, a transit (or astronomical transit) is the passage of a astronomical object, celestial body directly between a larger body and the observer. As viewed from a particular vantage point, the transiting body appears to move across the ...

in a quadruple star system, first known circumbinary planet in a quadruple star system, and the first planet in a quadruple star system found. It was the first confirmed planet discovered by PlanetHunters.org. An independent and nearly simultaneous detection was also reported from a revision of Kepler space telescope data using a transit detection algorithm.

Star system

The

giant planet A giant planet, sometimes referred to as a jovian planet (''Jove'' being another name for the Roman god Jupiter (mythology), Jupiter), is a diverse type of planet much larger than Earth. Giant planets are usually primarily composed of low-boiling ...

Neptune Neptune is the eighth and farthest known planet from the Sun. It is the List of Solar System objects by size, fourth-largest planet in the Solar System by diameter, the third-most-massive planet, and the densest giant planet. It is 17 t ...

-sized, about 20-55 Earth-masses (). It has a radius 6.2 times that of Earth. The star system is 7200

light year A light-year, alternatively spelled light year (ly or lyr), is a unit of length used to express astronomical distance, astronomical distances and is equal to exactly , which is approximately 9.46 trillion km or 5.88 trillion mi. As defined by t ...

s from Earth. The planet orbits a close

binary Binary may refer to: Science and technology Mathematics * Binary number, a representation of numbers using only two values (0 and 1) for each digit * Binary function, a function that takes two arguments * Binary operation, a mathematical op ...

, with a more distant binary orbiting at a distance, forming the quadruple star system. The star system has the Kepler Input Catalogue name

KIC 4862625 PH1b (standing for "Planet Hunters 1"), or by its NASA designation Kepler-64b, 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 H ...

as well as the designation

Kepler-64 PH1b (standing for "Planet Hunters 1"), or by its NASA designation Kepler-64b, 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 H ...

. The close binary (Aa+Ab) that the planet circles has an orbital period of 20 days. They form an

eclipsing binary A binary star or binary star system is a Star system, system of two stars that are gravity, gravitationally bound to and in orbit around each other. Binary stars in the night sky that are seen as a single object to the naked eye are often resolved ...

pair. The two stars are (Aa) 1.384

solar mass The solar mass () is a frequently used unit of mass in astronomy, equal to approximately . It is approximately equal to the mass of the Sun. It is often used to indicate the masses of other stars, as well as stellar clusters, nebulae, galaxie ...

()

F-type main-sequence star An F-type main-sequence star (F V) is a main-sequence, hydrogen-fusing star of spectral type F and luminosity class V. These stars have from 1.0 to 1.4 times the mass of the Sun and surface temperatures between 6,000 and 7,600 K.Tables ...

and (Ab)

red dwarf A red dwarf is the smallest kind of star on the main sequence. Red dwarfs are by far the most common type of fusing star in the Milky Way, at least in the neighborhood of the Sun. However, due to their low luminosity, individual red dwarfs are ...

. The planet orbits this binary pair in a 138.3-day orbit. The binary pairs have a separation of 1000 AUs. A photometric-dynamical model was used to model the

planetary system A planetary system is a set of gravity, gravitationally bound non-stellar Astronomical object, bodies in or out of orbit around a star or star system. Generally speaking, systems with one or more planets constitute a planetary system, although ...

of the close binary pair. The distant binary (Ba+Bb) have a pair separation of 60 AU. The two stars are (Ba)

G-type main-sequence star A G-type main-sequence star (spectral type: G-V), also often, and imprecisely, called a yellow dwarf, or G star, is a main sequence, main-sequence star (luminosity class V) of stellar classification, spectral type G. Such a star has about 0.9 to ...

and (Bb) red dwarf. The quadruple star system has an estimated age of two billion years (2 gigayears). The system is located at

right ascension Right ascension (abbreviated RA; symbol ) is the angular distance of a particular point measured eastward along the celestial equator from the Sun at the equinox (celestial coordinates), March equinox to the (hour circle of the) point in questio ...

declination In astronomy, declination (abbreviated dec; symbol ''δ'') is one of the two angles that locate a point on the celestial sphere in the equatorial coordinate system, the other being hour angle. The declination angle is measured north (positive) or ...

, so also has a

2MASS The Two Micron All-Sky Survey, or 2MASS, was an astronomical survey of the whole sky in infrared light. It took place between 1997 and 2001, in two different locations: at the U.S. Fred Lawrence Whipple Observatory on Mount Hopkins, Arizona, and ...

catalogue entry of ''

2MASS 19525162+3957183 PH1b (standing for "Planet Hunters 1"), or by its NASA designation Kepler-64b, is an extrasolar planet found in a circumbinary planet, circumbinary orbit in the Star system#Quaternary, quadruple star system Kepler-64. The planet was discovered b ...

''Kepler Catalogue, KIC 4862625

Discovery

Kian Jin Jek (Chinese: 易建仁, son of

Jek Yeun Thong Jek Yeun Thong ( zh, s=易润堂, p=Yì Rùntáng; 29 July 1930 – 3 June 2018) was a Singaporean politician who served as Minister for Science and Technology between 1976 and 1977, Minister for Culture between 1968 and 1977 and Minister fo ...

), 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 Christopher John Lintott (born 26 November 1980) is a British astrophysicist, author and broadcaster. He is a Professor of Astrophysics in the Department of Physics at the University of Oxford, and, since 2023, Gresham Professor of Astronomy ...

, from Oxford University. 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. At the time of discovery, it was the sixth known circumbinary planet.

Role as a benchmark system

The planet PH1b and were used as a benchmark system for automated detection algorithms. As a benchmark system PH1 is used to improve the algorithm and to demonstrate improvement in the detection of circumbinary planets.

Star system

Discovery

Role as a benchmark system

See also

References

Further reading