Abstract
The properties of the recently discovered1,2 extrasolar planets were not anticipated by theoretical work on the formation of planetary systems, most models for which were developed to explain our Solar System. Indeed, the observational technique used to detect these planets (measurement of radial-velocity shifts in stellar spectral lines) do not yet have the sensitivity to detect planetary systems like our own3. Here we report observations and modelling of the gravitational microlensing event MACHO-97-BLG-41. We infer that the lens system consists of a planet of about 3 Jupiter masses orbiting a binary stellar system consisting of a late-K dwarf star and an M dwarf. The stars are separated by ∼1.8 astronomical units (1 AU is the Earth–Sun distance), and the planet is orbiting them at a distance of about 7 AU. We had expected to find first the microlensing signature of jovian planets around single stars, so this result suggests that such planets orbiting short-period binary stars may be common.
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Acknowledgements
The authors are members of the MPS Collaboration and the Wise Observatory GMAN Team. We thank the MACHO, OGLE and EROS collaborations for announcements of microlensing events in progress, and the MACHO team for their discovery of MACHO-97-BLG-41. We also thank W. Sutherland for access to his likelihood estimation code. This work was supported in part by the NASA Origins program, the US NSF and a Research Innovation Award for the Research Corporation. Work performed at MSSSO is supported by the Australian Department of Industry, Technology and Regional Development. Work performed at UW is supported in part by the Office of Science and Technology Centers of NSF. Astronomy at Wise Observatory is supported by the Israel Science Foundation.
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Bennett, D., Rhie, S., Becker, A. et al. Discovery of a planet orbiting a binary star system from gravitational microlensing. Nature 402, 57–59 (1999). https://doi.org/10.1038/46990
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DOI: https://doi.org/10.1038/46990
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