1 in 5 stars have earth-like planets around them!

Discussion in 'Science and Technology' started by Romulan_spy, Nov 4, 2013.

  1. Romulan_spy

    Romulan_spy Commodore Commodore

    Joined:
    Sep 8, 2000
    Location:
    Terre Haute, IN. USA
  2. publiusr

    publiusr Rear Admiral Rear Admiral

    Joined:
    Mar 22, 2010
    Lets hope they aren't all scorchers like the most recent of them.
     
  3. Metryq

    Metryq Fleet Captain Fleet Captain

    Joined:
    Jan 23, 2013
    "Earth-like" is the term journalists and scientists with a sensationalist flair use for Earth mass planets. And the so-called "habitable zone" is pure conjecture.

    Once upon a time there were canals on Mars and rain forests on Venus.

    Exoplanetary astronomy is exciting, but we hear about "Earth-like" planets almost as often as we hear about Voyager leaving the Solar system and entering interstellar space.
     
  4. Ronald Held

    Ronald Held Rear Admiral Rear Admiral

    Joined:
    Feb 21, 2005
    Location:
    On the USS Sovereign
    Not certain how much this actually is valid.
     
  5. Lindley

    Lindley Moderator with a Soul Moderator

    Joined:
    Nov 30, 2001
    Location:
    Bonney Lake, WA
    Earth-like in the sense that both Antarctica and the Sahara are "Earth-like" environments. Only less similar, probably.
     
  6. scotpens

    scotpens Vice Admiral Admiral

    Joined:
    Nov 29, 2009
    Location:
    Los Angeles, CA
    You mean there aren't?

    Damn.
     
  7. Ensign_Redshirt

    Ensign_Redshirt Commodore Commodore

    Joined:
    Aug 3, 2007
    Yeah, um, when astronomers talk about "Earth-like planets" they don't mean Class-M planets like on Star Trek. They basically mean planets similar to Earth, Venus, or Mars. And compared to Jupiter or Mercury, Venus is in fact very Earth-like. Doesn't mean you can breath there though.
     
  8. chrisspringob

    chrisspringob Commodore Commodore

    Joined:
    Jan 12, 2003
    Location:
    North Ryde, NSW
    And this isn't really "1 in 5 stars", is it? As I understand it, it's 1 in 5 "Sun-like stars".
     
  9. Metryq

    Metryq Fleet Captain Fleet Captain

    Joined:
    Jan 23, 2013
    Astronomers refer to "Terrestrials" and "Jovians." Perhaps those are antiquated terms now, I don't know. But I would not call Venus "Earth-like." Mercury is a "Terrestrial," yet much more like the Moon than Earth—or Venus.

    As for the "habitable zone" argument, the Earth and Moon are in the same zone, and several theories describe the Moon fissioning off from Earth. So why doesn't it have at least one sixth the atmosphere of Earth and some of Earth's other attributes? If life is ever found on Titan, for example, that would scrap the "habitable zone" argument.

    The point is, journalists or astronomers quoted as saying "Earth-like" is imprecise and very misleading... especially when one considers the hair-splitting that went into redefining Pluto—a subject some people feel passionately about. Sloppy language does not lead to sloppy thinking, but it can. In the same fashion, precise language, such as the practice of using "significant figures," even when it is zero, is a hallmark of science.

    All these exoplanetary reports should be using terms like "Earth-sized" or "Earth mass," but that doesn't excite the mouth-breathers like "Earth-like." We can pack up the space camper and go right now!
     
  10. B.J.

    B.J. Rear Admiral Rear Admiral

    Joined:
    Jul 14, 2004
    Location:
    Huntsville, AL
    A lot of that has to do with the the moon only getting some of the lighter materials, and not stuff like the iron core. I don't have a lot of time right now (in a meeting at work! :alienblush:), so I'll let others expand on that.

    "Habitable zone" only takes into account the star. It doesn't take into account other factors like the planet or moon having internal heat due to gravitational stresses.
     
  11. Metryq

    Metryq Fleet Captain Fleet Captain

    Joined:
    Jan 23, 2013
    My point was that being within the "habitable zone" does nothing to increase the "chances" that the planet is suitable for a biosphere.

    Gravitationally induced heat, or the local star(s) are far from the only sources of heat or energy. And we're still learning the subtleties of Earth's energy economy.
     
  12. CorporalCaptain

    CorporalCaptain Admiral Admiral

    Joined:
    Feb 12, 2011
    Location:
    Gene's office
    That seems like a rather strong statement. Does nothing? Really?

    What about radioactive decay?
     
  13. Lindley

    Lindley Moderator with a Soul Moderator

    Joined:
    Nov 30, 2001
    Location:
    Bonney Lake, WA
    I think it's fairly obvious that p(biosphere | habitable zone) > p(biosphere | !habitable zone).
     
  14. scotpens

    scotpens Vice Admiral Admiral

    Joined:
    Nov 29, 2009
    Location:
    Los Angeles, CA
    Could you please explain that formula in layman's language? :confused: I never got any higher in math than first-year algebra.
     
  15. Lindley

    Lindley Moderator with a Soul Moderator

    Joined:
    Nov 30, 2001
    Location:
    Bonney Lake, WA
    The probability of a biosphere given that a planet is in the habitable zone is greater than the probability of a biosphere given that a planet is not in the habitable zone.

    This does not say a biosphere is likely, just that it's more likely by a nonzero amount.
     
  16. publiusr

    publiusr Rear Admiral Rear Admiral

    Joined:
    Mar 22, 2010
    A good many of these may be the hot earths like what was recently seen--or Venus clones. Find some with a big moon and plate tectonics---and watch those...