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The star HD 136118 (Digitized Sky Survey image)
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February 7, 2002
(PLANETQUEST) -- A planetary companion has been detected circling the star HD 136118, bringing to 76 the total number of planets thus far discovered orbiting stars other than our Sun.
The discovery was made by a team of astronomers carrying out precise Doppler observations at California's Lick Observatory. Their method of detection, called radial velocity, or Doppler spectroscopy, infers the presence of an unseen companion because of the back-and-forth movement it induces in the host star. This movement is detectable as a periodic red shift and blue shift in the star's spectral lines. (For more about this method, see the article Finding Planets.)
With a magnitude of 6.9, this F8 star is visible to the unaided eye (under optimal circumstances) just north of the constellation Libra at a distance of 170 light years (52.3 parsecs). It is slightly larger than our Sun, and may be evolving away from its main sequence to become a red giant -- a process that will eventually take place with our own Sun.
The planetary companion is a gas giant with a derived mass roughly 12 times that of Jupiter. Its orbit lasts more than three years. Like the majority of extrasolar planets discovered, it follows a highly eccentric, or oval, orbital path.
The discovery was announced by Debra A. Fischer, Geoffrey W. Marcy and Bernie Walp of the University of California; and R. Paul Butler of the Carnegie Institution, Steven S. Vogt of the Lick Observatory and Keven Apps of the University of Sussex.
The team is carrying out a Doppler survey of about 350 stars at the Lick Observatory and Hawaii's W.M. Keck Observatory.
