PH1b
First transiting circumbinary planet found in a quadruple star system.
PH1b (also designated Kepler-64b) is an extrasolar planet discovered in a circumbinary orbit within the quadruple star system Kepler-64. It is notable as the first known transiting planet in a quadruple star system, the first known circumbinary planet in such a system, and the first planet in a quadruple star system found. The discovery was announced on 15 October 2012 and was the first confirmed planet discovered by the Planet Hunters project.
Quick Facts
- Discoverer
- Planet Hunters
- Discovery Site
- Kepler space telescope
- Discovered
- 15 October 2012
- Discovery Method
- Transit
- Apsis
- astron
- Semimajor
- 0.634 ± 0.011 AU
- Period
- 138.506 · +0.107 · -0.092 d
- Star
- Kepler-64 / PH1
- Single Temperature
- 481 K
Facts from the source article.
Lore & Background
The planet PH1b was discovered by two amateur astronomers, Kian Jin Jek from San Francisco and Robert Gagliano from Cottonwood, Arizona, using data from the Kepler space telescope through the Planet Hunters project. Kian Jek first spotted a light dip indicative of a transit in May 2011, and later reported a second. Robert Gagliano performed a systematic search, confirmed the second dip, and found a third in February 2012. Using these observations, Kian predicted another transit and found it. The planet was subsequently detected by the eclipsing binary timing variation method. At the time of discovery, it was the sixth known circumbinary planet.
The planet is Neptune-sized, with a mass of 20–55 Earth masses and a radius 6.2 times that of Earth. It orbits a close binary pair (Aa+Ab) consisting of a 1.384 solar mass F-type main-sequence star and a 0.336 solar mass red dwarf, which have an orbital period of 20 days and form an eclipsing binary. The planet's orbit around this binary is 138.3 days. A more distant binary (Ba+Bb), with a pair separation of 60 AU, orbits at a separation of 1000 AU, making the system a quadruple star system. The stars in the distant binary are a 0.99 solar mass G-type main-sequence star and a 0.51 solar mass red dwarf. The system is estimated to be two billion years old and lies 7200 light years from Earth.
Reader's Guide
PH1b holds significance as a benchmark system for automated detection algorithms. Along with Kepler-35b, it was used to improve algorithms and demonstrate progress in detecting circumbinary planets. Its discovery by amateur astronomers through the Planet Hunters project highlights the role of citizen science in exoplanet research. The planet was the first confirmed planet found by PlanetHunters.org, and an independent, nearly simultaneous detection was also reported from a revision of Kepler data using a transit detection algorithm. The system's quadruple-star nature makes it a unique laboratory for studying planetary formation and orbital dynamics in complex stellar environments. The photometric-dynamical model used to characterize the planetary system of the close binary pair provided a method for confirming the planet's existence and orbit.
Did You Know?
- The planet orbits a close binary pair that is itself part of a quadruple star system.
- The system is located 7200 light years from Earth and is estimated to be two billion years old.
Frequently Asked Questions
What is PH1b?
PH1b, also catalogued as Kepler-64b, is an extrasolar planet that orbits within a quadruple star system roughly 7,200 light-years from Earth. It follows a circumbinary path around all four stars, completing one orbit in about 138 days.
How was PH1b discovered?
Amateur astronomers Kian Jin Jek and Robert Gagliano spotted the signal while participating in the Planet Hunters citizen-science project, and the find was formally announced on 15 October 2012. It stands as the first confirmed planet identified through that particular platform.
What makes PH1b unique among known exoplanets?
It is the first planet ever detected in a quadruple star system and the first transiting circumbinary planet found in such a configuration. Before its identification, no exoplanet had been confirmed orbiting all four members of a quadruple system.
What are PH1b's size and mass?
The planet has a radius about 6.2 times that of Earth and a mass estimated between 20 and 55 Earth masses, placing it in the sub-Neptune category.
Why does PH1b matter to the amateur astronomy community?
Its discovery demonstrated that volunteer stargazers working with publicly available data could produce a genuine first-of-its-kind planetary find, validating the Planet Hunters citizen-science model. It remains a landmark example of non-professional astronomers contributing a novel discovery to the field.
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