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Telescopes and space missions

Telescopes and space missions

Planet controversy ends

06 Jan 1998

Three years ago astronomers believed they had discovered the first evidence of a planet orbiting a G-type star. More recent data disagreed with this assessment. Now new observations by some of the leading skeptics have lead them to change their minds, and confirm the existence of the planet.

The new evidence is published in this week’s Nature. Two papers, one by David Gray of the University of Western Ontario, and one by Artie Hatzes of the University of Texas, Austin, describe new information that indicates a planet orbiting the star 51 Pegasi.

The planet was originally discovered by Michel Mayor and Didier Queloz of the Geneva Observatory. They studied doppler shift patterns in the star’s spectral absorption lines. Their calculations suggested the planet was approximately half Jupiter’s mass and moved in a very close orbit around the star. At the time, this small orbit made some astronomers skeptical that such an object could really exist.

Gray pointed out that the star could generate periodic oscillations producing doppler shift patterns similar to those seen by Mayor and Queloz. His new data now refutes this theory: “a planet may indeed be the best explanation for the radial-velocity results” he writes. In a connected paper Hatzes and his colleagues describe some high resolution results that are consistent with the existence of a planetary companion to 51 Pegasi.

Last week astronomers in Toronto published a paper which indicated a mechanism for Jupiter mass planets to move from outlying orbits to smaller orbits (Science 279 69-72, 1998). Together the three papers increase the likelihood that doppler shifts in our neighboring stars really are generated by massive planets.

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