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Kepler22b-first exoplanet found in hab-zone of sun-like star

  1. Dec 5, 2011 #1

    marcus

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    Kepler22b--first exoplanet found in hab-zone of sun-like star

    http://science.nasa.gov/science-news/science-at-nasa/2011/05dec_firstplanet/

    NASA newsletter
    ==quote==
    Kepler Confirms First Planet in Habitable Zone of Sun-like Star
    Dec 5, 2011: NASA's Kepler mission has confirmed its first planet in the "habitable zone" of a distant sun-like star.

    The newly confirmed planet, Kepler-22b, is about 2.4 times the radius of Earth. Scientists don't yet know if Kepler-22b has a predominantly rocky, gaseous or liquid composition, but its discovery is a step closer to finding Earth-like planets1.

    The "habitable zone" of a planetary system refers to the band of orbits where liquid water could exist on a planet’s surface. Kepler has recently discovered more than 1,000 new planet candidates. Ten of these candidates are near-Earth-size and orbit in the habitable zone of their host star. Candidates require follow-up observations to verify they are actual planets.

    "This is a major milestone on the road to finding Earth's twin," said Douglas Hudgins, Kepler program scientist at NASA Headquarters in Washington.
    Kepler-22b is located 600 light-years away. While the planet is larger than Earth, its orbit of 290 days around a sun-like star resembles that of our world. The planet's host star belongs to the same class as our sun, called G-type, although it is slightly smaller and cooler.

    Kepler discovers planets and planet candidates by measuring dips in the brightness of more than 150,000 stars.
    ==endquote==
     
    Last edited: Dec 5, 2011
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  3. Dec 5, 2011 #2

    Drakkith

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    Re: Kepler22b--first exoplanet found in hab-zone of sun-like star

    Excellent! Any idea on what the mass of the planet is? I didn't see anything on it.
     
  4. Dec 5, 2011 #3

    Chronos

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    Re: Kepler22b--first exoplanet found in hab-zone of sun-like star

    That is a bit more difficult since planetary masses are typically much smaller than the host star, the difference between orbital period due to mass is virtually negligible under Kepler's Law. The volume of Kepler-b22 is nearly 14 times that of earth, hence, is probably much more massive than earth even if its density is relatively low.
     
  5. Dec 5, 2011 #4

    Drakkith

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    Re: Kepler22b--first exoplanet found in hab-zone of sun-like star

    I see. I was hoping to be able to caculate the surface gravity!
     
  6. Dec 5, 2011 #5

    marcus

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    Re: Kepler22b--first exoplanet found in hab-zone of sun-like star

    Drakkith, it's worth noting that the Kepler planet search does not use the wobble method.
    When planets are detected by the wobble of the host star one can reckon their mass compared with the star's, and one can use long-established means to judge the star mass.

    Perhaps a wobble study will be done on this system, but it will take time because the period is over 200 days. Then we will know things like mass, and density, and have a guess as to what material---so be able to infer more about it.

    Kepler only finds exoplanets which pass between us and the host star. It measures dips in the lightcurve. The tradeoff is that it can study many stars at once. Detecting a dip in the lightcurve is much less elaborate than recording the very slight wobble by fine doppler measurement.

    I sympathise with any feeling of frustrated curiosity. I would like to know more myself. All we know so far is that there is a G-type star that has a planet roughly twice the size of earth which could be the right temperature for liquid water.

    Kepler has found a bunch of candidates so presumably we will be hearing more about this and several others as well.
     
  7. Dec 5, 2011 #6

    Drakkith

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    Re: Kepler22b--first exoplanet found in hab-zone of sun-like star

    That makes sense Marcus. I'm part of planethunters.org myself. Maybe I'll help find a planet or two myself.
     
  8. Dec 5, 2011 #7

    marcus

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    Re: Kepler22b--first exoplanet found in hab-zone of sun-like star

    Then you probably could tell me stuff I don't know about the various methods! I'll look up planethunters.org and see what it says the volunteer hunters do. So far it's been missing from my education :biggrin:
     
  9. Dec 5, 2011 #8

    DaveC426913

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    Re: Kepler22b--first exoplanet found in hab-zone of sun-like star

    But let us not forget that a planet's surface gravity - even with constant density - does not climb as quickly as its mass.
     
  10. Dec 5, 2011 #9

    marcus

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    Re: Kepler22b--first exoplanet found in hab-zone of sun-like star

    Then you probably could tell me stuff I don't know about the various methods! I'll look up planethunters.org and see what it says the volunteer hunters do. So far it's been missing from my education :biggrin:

    Wow! it's nicely set up. A beginner immediately gets to try identifying transit events (dips in the lightcurve as something like a planet passes in front.)

    So you are working on Kepler data. Bravo for taking that kind of initiative!

    (Or Brava as the case may be. :-) )
     
  11. Dec 5, 2011 #10

    Drakkith

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    Re: Kepler22b--first exoplanet found in hab-zone of sun-like star

    Yeah, its pretty interesting. There are some CRAZY light curves there. Most are just kinda random bleh...
     
  12. Dec 5, 2011 #11

    D H

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    Re: Kepler22b--first exoplanet found in hab-zone of sun-like star

    It measures the dips so well that it enabled NASA to publish images of it. :rolleyes:

    The image from NASA all over the internet. No "Artist Rendition" caption. I'm mildly annoyed.
     
    Last edited: Dec 5, 2011
  13. Dec 5, 2011 #12

    Drakkith

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    Re: Kepler22b--first exoplanet found in hab-zone of sun-like star

    Umm, what?
     
  14. Dec 5, 2011 #13

    marcus

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    Re: Kepler22b--first exoplanet found in hab-zone of sun-like star

    Indeed! Just for fun we could imagine this thing has similar density to Earth and as they say 2.4 times the radius we could suppose 2.4 times the surface gravity and 2.4 times the escape velocity. All just wild guesses.

    The higher escape velocity suggest it may have retained more atmosphere and volatile stuff and have a denser atmosphere. Too early to start speculating what that could mean.

    Butterflies anyone? Birds? I hope their greenhouse isn't too bad. I don't like really hot days.
    ======================
    @DH
    I agree it is annoying when people drop off the "ARTIST CONCEPTION" caveat and spread it around like a real photograph.
     
  15. Dec 5, 2011 #14

    D H

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    Re: Kepler22b--first exoplanet found in hab-zone of sun-like star

    Just do a google image search for Kepler-22b. My local news presented this image as if it was a photo taken by the Kepler satellite. Lots of news stories are presenting it as the same.

    The mission page for the mission presents the image as the first thing you see when you enter the site. There is no mention on this page that the image of Kepler-22b is an artist's conception. They at least do say this in the detail pages.
     
  16. Dec 5, 2011 #15

    marcus

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    Re: Kepler22b--first exoplanet found in hab-zone of sun-like star

    @Dave,
    please read what I wrote.
    ===========

    @DH
    I googled "Kepler-22b" and the first hit had the picture WITH the caption "Artist rendering".

    It was the online NY Daily News and it said it was Associated Press.
    So maybe we have a mix of good and bad journalism here. You saw some bad but the top google hit is correctly captioned.
     
  17. Dec 5, 2011 #16

    D H

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    Re: Kepler22b--first exoplanet found in hab-zone of sun-like star

    If density remains the same as the Earth's and the radius is twice that of the Earth, the mass is eight times that of the Earth. Gravitational acceleration doubles.
     
  18. Dec 5, 2011 #17

    DaveC426913

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    Re: Kepler22b--first exoplanet found in hab-zone of sun-like star

    Of course I read what you wrote. (I don't now why people say this.)



    I've retracted my former claim because I am doubting its veracity.

    I could have sworn that (assuming a fixed density) - as a planet's radius increases and its mass increases - its surface gravity does not go up as fast as its mass. This is because the radius is increasing, putting the surface farther from the CoM.

    Now I'm not so sure. And it's too late this evening to check.
     
  19. Dec 5, 2011 #18

    marcus

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    Re: Kepler22b--first exoplanet found in hab-zone of sun-like star

    No one suggested that mass doubles --> surface gravity doubles. What were you contradicting?
    In my post I suggested OTBE that radius doubles --> surface gravity doubles.

    Or in this case let the factor be 2.4 instead. I asked you to read my post again so you would realize what I said was right, and did not call for a "What? No." reaction.
     
  20. Dec 5, 2011 #19
    Re: Kepler22b--first exoplanet found in hab-zone of sun-like star

    Very interesting and very exciting times we live in! Although it does pose some questions.
    According to wikipedia (which I'm pretty sure has never been wrong about anything), that when using the transit method, if the planet passes both in front of, and behind the star (relative to earth), we should be able to detect its temperature and elements of its atmosphere, and possibly even if it has clouds! Although no mention of this...
    Do we then assume they didn't mention this because it didn't transit behind the star relative to us? Or did they just not bother to mention it because they didn't realize there would be this much excitement? Obviously the latter can't be possible (unless they are really really dense).
    Edit: the link to wikipedia:
    http://en.wikipedia.org/wiki/Transit_method#Transit_method
     
  21. Dec 6, 2011 #20

    Drakkith

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    Re: Kepler22b--first exoplanet found in hab-zone of sun-like star

    The Kepler satellite is not equipped to do that kind of analysis. It merely looks at light curves.
     
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