Research ArticlesAstronomy

Direct imaging discovery of a Jovian exoplanet within a triple-star system

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Science  12 Aug 2016:
Vol. 353, Issue 6300, pp. 673-678
DOI: 10.1126/science.aaf9671

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Spying a planet in a triple-star system

Thousands of extrasolar planets are now known, but only a handful have been detected in direct images. Wagner et al. used sophisticated adaptive optics to discover a planet in images of the triple-star system HD 131399 and to take a spectrum of its atmosphere (see the Perspective by Oppenheimer). The planet, about four times the mass of Jupiter, orbits around one star in the system while the other two stars move farther out. This unusual arrangement is puzzling: The planet's orbit may be stable, but it is unclear how it could have formed or migrated there. The results will be used to refine theories of planet formation.

Science, this issue p. 673; see also p. 644


Direct imaging allows for the detection and characterization of exoplanets via their thermal emission. We report the discovery via imaging of a young Jovian planet in a triple-star system and characterize its atmospheric properties through near-infrared spectroscopy. The semimajor axis of the planet is closer relative to that of its hierarchical triple-star system than for any known exoplanet within a stellar binary or triple, making HD 131399 dynamically unlike any other known system. The location of HD 131399Ab on a wide orbit in a triple system demonstrates that massive planets may be found on long and possibly unstable orbits in multistar systems. HD 131399Ab is one of the lowest mass (4 ± 1 Jupiter masses) and coldest (850 ± 50 kelvin) exoplanets to have been directly imaged.

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