LASP-operated spacecraft discovers rare four-star planet

Using data from the LASP-operated Kepler spacecraft, citizen scientists helped discover planet PH1, the only recorded circumbinary planet in a four-star system. This artist’s depiction illustrates the planetary system, with PH1 in the foreground. (Courtesy Haven Giguere/Yale)

With key help from citizen scientists, the LASP-operated NASA Kepler spacecraft has discovered a unique planet orbiting a double-star system; the system is, in turn, orbited by two additional stars. Amateur astronomers and scientists aided the discovery through the Yale University Planet Hunters citizen-science program.

The newly discovered planet, PH1, is the first reported case of what is known as a circumbinary planet in a four-star system. PH1 is slightly larger than Neptune, is thought to be a gas giant, and revolves around its two central stars approximately once every 138 days. The outer pair of stars orbits the entire planetary system from about 1,000 astronomical units (AU) away—roughly 900 times the distance between the Sun and Earth, according to NASA.

Kepler surveys our Galaxy for planets in the habitable zone where liquid water, and potentially life, may exist on a planet’s surface. Citizen scientists first made the PH1 discovery using the website. A Yale-led international team of professional astronomers later confirmed the planet’s existence.

Kepler’s new discovery is rare: PH1 is one of only seven known planets to orbit two stars, and no faraway pairs of stars orbit the other six planetary systems.

LASP manages Kepler Mission Operations from our CU-Boulder facilities, and trains students to operate the spacecraft under the guidance of LASP professionals. For more information about the LASP Mission Operations & Data Systems group, please visit

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