Why is the transit method used more than the wobble method?

Discussion in 'Science and Technology' started by ThankQ, Feb 8, 2012.

  1. ThankQ

    ThankQ Fleet Admiral Admiral

    Joined:
    Mar 27, 2003
    Location:
    Omnipresent
    The transit method of exoplanet detection relies upon the disk of the system to be edge on to our point of view.

    It seems the wobble method would be able to detect wobble from any angle. Or does the wobble method depend on the Red/Blue Shift, only being able to detect if a star is moving closer/farther? Can the wobble method only detect to-and-fro, or can it detect left-and-right if we were viewing a system from above/below?

    As far as we can detect, do most systems share the plane of the Milky Way galaxy or is it a pretty random assortment of orientations? For that matter, is the plane of our system level with the plane of the galaxy or are we at an angle?

    EDIT: Sorry, for light I suppose it would be the Red Shift or Hubble Shift. I had posted "Doppler". My bad.
     
  2. Pavonis

    Pavonis Commodore Commodore

    Joined:
    Apr 26, 2001
    I think the radial velocity method is used more than the transit method. At least, all the statistics I've found indicate that.
     
  3. B.J.

    B.J. Rear Admiral Rear Admiral

    Joined:
    Jul 14, 2004
    Location:
    Huntsville, AL
    Basically, yes the wobble method can only detect the star's motion towards and away from us. A side effect of that is that whatever planets we detect that way, we can only determine their *minimum* mass. So if a star system has planets whose orbits are highly inclined to our line of sight, the star won't seem to wobble quite as much to us.

    As for the orientation of the Solar System to the galaxy, no they're not aligned. I won't get into specifics, but even just looking at the night sky you can see that the Milky Way is not in the same plane as the ecliptic.
     
  4. ThankQ

    ThankQ Fleet Admiral Admiral

    Joined:
    Mar 27, 2003
    Location:
    Omnipresent
    Get as specific as you like :) You sound like you're in the know.

    I'm always looking for good sources geared for the inquisitive, self-(semi)educated layman. You know, things that fall between Discovery/History Channel documentaries which tend to be glorified science cartoons (once you've seen 15 or 20 there isn't much more you can get from new ones), and the higher-math-heavy academic journals which become hard for me to hang with once the math gets beyond a high school level (I took three college hours of "Math Structures", a.k.a "Poet's Math", the minimum gen ed requirement for an English/Music double major).

    I do, however, have great interest in science, particularly the astronomy/cosmology/physics/astrophysics family--just not enough interest to learn calculus. :)

    As some of the highly perceptive among you may have noticed, I'm a big fan of Sagan's, and the greatest reason for that is his poetic writing style. Of course, I've run through his books and unless Ann Druyan starts publishing all those boxes and files that make me so jealous, there aren't going to be many more forthcoming.


    Well duh. I should have thought of that. To be fair to myself, it's not often you catch a glimpse of the Milky Way from midtown Tulsa, though I've certainly seen enough sky charts that I should have figured that one out.


    Interesting. Its the opposite for me. It seems like every video I see and article or book I read about exoplanet discoveries cites the transit method. Of course, I suppose that is to be expected with most of them seeming, these days, to come from Kepler.
     
  5. Scout101

    Scout101 Admiral Admiral

    Joined:
    Aug 21, 2003
    Location:
    Rhode Island, USA
    Problem with the wobble method is, in large part, the freaking distances involved! We're not talking about huge wobble variations, and the distance is incredible, so trying to determine if it's really happening, and significant enough to be because of a planet, it's difficult.

    You can see if there's wobble in the spinning basketball on my finger from standing next to me. try doing it from your house ;)

    More ways you have to try and determining something, the better the chance of finding something that stands out.
     
  6. B.J.

    B.J. Rear Admiral Rear Admiral

    Joined:
    Jul 14, 2004
    Location:
    Huntsville, AL
    Not really, I just know enough to be dangerous. :D Anyway, you know that Earth's north pole (celestial pole) points towards Polaris. The ecliptic north pole is in the constellation Draco, and the galactic north pole is in the vicinity of Arcturus. (Yeah, those are wikipedia links, but it's good for a starting point.)

    If you want a visual aid, here's a star map in the celestial coordinate system. The green line is the plane of the ecliptic, and you can of course see the Milky Way (galactic plane).