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Extrasolar Planet Detected Visually

Posted by jamie on from the nice-painting dept.

"etphonehome" was the first of many to submit this. Astronomers at UC-Berkeley measured a star decreasing in brightness as its planet crossed in front of it. This is the first known planet whose orbital plane crosses Earth, making this measurement possible. It's great to see independent confirmation of the "wobble" which until now has been the only evidence of extrasolar planets. There's a splendid artist's rendition on the astronomers' webpage; see also the story on CNN or the technically-challenged Washington Post ("the planet had indeed cast a shadow over the star").

3 of 96 comments (clear)

  1. Re:question about 'shadows' by Anonymous Coward · · Score: 5
    They did not, properly speaking, see a shadow on the sun. That was a bit of ignorant journalism in the Washington Post article, I guess. I didn't read that one.

    What happened is that a very large planet moved in its orbit of the other star into a position between that star and Earth. Thus, it blocked some of the light from the star from reaching earth, making the star appear to dim for a few moments...think of it as a very partial eclipse of that star by one of its planets, much like our moon occasionally gets between us and the sun, causing partial or total eclipses, blocking or dimming it briefly.

    This dimming of the star, predicted by the astronomers, proved that they had inferred its orbit coreectly, and that there are indeed other planets. Even if they are obscenely close to thier stars. A 3-4 day orbit means that thing is very very close to its sun - the weird thing is they've detected a lot of planets with about the same distance from various stars...

    Where are all the planets that have nice, decent, life supporting orbits? (ok ok , life-as-we-know-it style? I don't want to emigrate to Mercury or its distant kin!!)

  2. Extrasolar Planet by waldeaux · · Score: 5
    Actually, the transit that was reported was discovered by Greg Henry, of TSU using telescopes at Fairborn Observatory (south of Tuscon, AZ).

    These telescopes do the most precise photometry ever achieved, working to about 0.001 magnitudes on a night-to-night basis, and about 0.0002 mags for long-term variations. That's ALMOST good enough to montior irradiance changes for stars that vary as little as the Sun does. On a very good night, with lots of overlapping data, these telescopes could almost detect a transit of an Earth-sized planet.

    There are two published papers on using these telescopes to look for transits in exoplanet systems. A third has been accepted for publication by the Astrophysical Journal and will come out in the March 10, 2000 issue. (I'm one of the authors.) Preprints of the papers are all available on one of my webpages:

    (I'll get the preprint of the 3rd paper up there on Monday.)

    It's great to see that a transit has finally been observed! We were starting to get worried... The search for transits is being done in collaboration with a long-term program to better understand the stars they orbit also done at Fairborn and with Mount Wilson's HK Project.

    Bob Donahue

  3. Re:CNN scientifically challenged too by astrophysics · · Score: 4

    Good question. If current theories are correct then they did not form there, but rather migrated after forming at several AU. The fact that one is observed to be a gas giant supports this since gas giants are beleived to form at several AU.

    How did they move? At the moment, there are several hypotheses, each with it's own problems. To summarize:

    1. Interaction with a gaseous disk to transport angular momentum outward and mass inward by exciting spiral density waves at Lindblad resonances (distance at which the orbital frequency matches the frequency of radial oscilation of the planet in an epicyclic approximation) on both sides of the planet's orbit. Big problems: Effects of additional planets, how to stop the migration right before it falls into the star

    2. Interaction with a planetessimal disk in which many small bodies at orbital resonances (where ratio of the two orbital periods is a rational) have their eccentricities excited so they can be kicked out of the system by the planet in a close encounter. Big problems: Effects of additional planets, need a very massive disk for the process to be unstable (and thus significant migration).

    3. Interation with other planets so that one planet gets kicked farther out (sometimes out of the system entirely) and another planet closer in, or two collide. Big problems: Can this send enough planets so close to their star to match observations?

    4. Interactions with another (more distant) star that induces a long term secular increase in the eccentricity until tidal effects before important and circularize the orbit at a small radius. Big problems: Quadrupole moment of star may limit eccentrity. Some planets are around star with no observed wide binary companion.

    If you want references to any of these, I can provide them.