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Starlight Measurements to Size Up a Planet

Posted by michael on from the about-the-size-of-my-thumb dept.

Overcoat writes "NASA scientists have used a technique called 'astrometry' to determine the size of a planet orbiting Gliese 876, a star 15 light years away from our solar system. By measuring tiny changes in the 'tilt' of light emitted from the star, changes which were caused by the force exterted by the orbiting planet known as Gliese 876b, the scientists were able to determine that the planet is the size of a golfball. Just kidding: the planet's a whopper, coming in at between 1.89 and 2.4 times the size of Jupiter. This marks the first time astrometry, usually used to measure the distance between stars, has been used to measure a planet."

3 of 23 comments (clear)

  1. Density? by Lord+Bitman · · Score: 3, Insightful

    Wouldnt these measurements be more effected by the planet's Density than its actual size?

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    1. Re:Density? by Henry+V+.009 · · Score: 3, Insightful

      You mean mass. The scientists are able to find the mass by these measurements. Of course, since it's a gas giant, the density (and therefore size) is fairly standard.

  2. More information here by Simon+Field · · Score: 5, Insightful


    Some other astrometry uses of the Fine Guidance Sensors can be found here: HST Astrometry Science Team.

    I was looking for something a little less lame, something that didn't talk about the "tilt" of the light. Are they measuring polarization? Refraction? Diffraction?

    Does anyone have a pointer to the article that UPI has so badly dumbed-down?

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