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Scientists Discover Exoplanet Less Than Twice the Mass of Earth

Snowblindeye writes with this excerpt from the European Southern Observatory: "Well-known exoplanet researcher Michel Mayor today announced the discovery of the lightest exoplanet found so far. The planet, 'e,' in the famous system Gliese 581, is only about twice the mass of Earth. The team also refined the orbit of the planet Gliese 581 d, first discovered in 2007, placing it well within the habitable zone, where liquid water oceans could exist. Planet Gliese 581 e orbits its host star — located only 20.5 light-years away in the constellation Libra ('the Scales') — in just 3.15 days. 'With only 1.9 Earth-masses, it is the least massive exoplanet ever detected and is, very likely, a rocky planet,' says co-author Xavier Bonfils from Grenoble Observatory. Being so close to its host star, the planet is not in the habitable zone. But another planet in this system appears to be. ... The planet furthest out, Gliese 581 d, orbits its host star in 66.8 days. 'Gliese 581 d is probably too massive to be made only of rocky material, but we can speculate that it is an icy planet that has migrated closer to the star,' says team member Stephane Udry. The new observations have revealed that this planet is in the habitable zone, where liquid water could exist. '"d" could even be covered by a large and deep ocean — it is the first serious "water world" candidate,' continued Udry."

24 of 201 comments (clear)

  1. Astronomy by Reorix · · Score: 5, Interesting

    I always hear about these sorts of discoveries, of new planets more and more similar to earth, but having almost no astronomy background, I have no idea how significant they are.

    How much do we really know about these planets, and how much is guessing? How close are these planets, really, to earth?

    1. Re:Astronomy by olsmeister · · Score: 5, Funny

      It's 20 (or so) light years from Earth. According to this article, we've probably already pissed off any inhabitants...

    2. Re:Astronomy by confused+one · · Score: 4, Informative

      The significance is that our methodology is improving. Only in the past decade or so have we been able to identify stars with possible planets. Only in the past year or two have we been able to directly image a planet (or separate it's image from the parent star). What we know of the planets is based on how close it's orbit is to the star, it's estimated mass, and in a few recent cases, based on limited spectroscopic information.

      Now that Kepler's working, over the next 2-3 years we should have a flood of these reports. (keep in mind Kepler's only imaging a 10 x 10 degree patch of sky) In the next decade we will develop the means to directly image a nearby terrestrial sized planet.

      All of the planets imaged so far are relatively close, on a galactic scale. A few 10's of light years. There's more than enough information out there to explain how far that is from a human perspective. Let's just say, that based on current technology, none of our great-grand children will get an up close look. (although I suppose we could do a fly by of something like the Gliese 581 system, with a probe, in the next 3-4 generations, if we tried hard enough.

    3. Re:Astronomy by jollyreaper · · Score: 3, Funny

      It's 20 (or so) light years from Earth. According to this [theregister.co.uk] article, we've probably already pissed off any inhabitants...

      We still have what, ten years left to invent an FTL drive and get there to preemptively apologize for reality television, right?

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  2. but what about Earth 2... by squoozer · · Score: 4, Insightful

    This is very interesting but no where near as exciting as finding another Earth like planet. I suppose we will have to wait for the next generation of telescopes before we find it though.

    What is a little surprising though is how many planetary systems we have found that are very different to our own. I can't believe ours is unique but perhaps it's quite rare.

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    1. Re:but what about Earth 2... by Chris+Burke · · Score: 5, Insightful

      This is very interesting but no where near as exciting as finding another Earth like planet. I suppose we will have to wait for the next generation of telescopes before we find it though.

      Well the 'e' planet is somewhat earth-like in mass and possibly earth-like in composition. It's not in the habitable zone for the star, but the closer a planet is to the star the easier it is to detect, and this exoplanet is at the very edge of our ability to detect (thus why this is news -- smallest exoplanet ever found). So you're right, we'll have to wait for technology to advance to find earth-sized rocky planets in the habitable zone (especially of non-dwarf stars).

      What is a little surprising though is how many planetary systems we have found that are very different to our own. I can't believe ours is unique but perhaps it's quite rare.

      I'm not sure anything we've found suggests that our type of solar system is rare. The limitations of our detection method by and large assures we'd find systems different from our own first. Astrophysicists might not have expected to find gas giants very close in to stars, but if they exist, we were going to find those first. The two main things that seem to have changed to me are that 1) we've gone from having nothing but our own solar system as an example and thus assuming ours was the model for all of them, to have many more examples showing different types and 2) we've learned that solar systems seem to be pretty common.

      If we get to the point where detecting a solar system like ours would be simple, and despite finding thousands of others we don't find any like ours, then maybe that points to rarity. Right now though I doubt we're anywhere near being able to say that.

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    2. Re:but what about Earth 2... by camperdave · · Score: 4, Funny

      It is known that there are an infinite number of worlds, simply because there is an infinite amount of space for them to be in. However, not every one of them is inhabited. Therefore, there must be a finite number of inhabited worlds. Any finite number divided by infinity is as near to nothing as makes no odds, so the average population of all the planets in the Universe can be said to be zero. From this it follows that the population of the whole Universe is also zero, and that any people you may meet from time to time are merely the products of a deranged imagination.

      --
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  3. Planets and moons by nizo · · Score: 3, Interesting

    Gliese 581 d is probably too massive to be made only of rocky material...

    Even if it isn't habitable, it might still be large enough to have a habitable moon perhaps?

    1. Re:Planets and moons by American+Terrorist · · Score: 5, Funny

      Only if you eradicate the ewoks first. God those things are annoying. But hopefully tasty.

    2. Re:Planets and moons by Robotbeat · · Score: 4, Informative

      One interesting thing about Gliese 581 d not being made of rock is that it might have almost the same surface gravity as Earth:

      Volume of a sphere=(4/3)*pi*radius^3
      radius of sphere=((.75/pi)*volume)^(1/3)
      volume=mass/density
      radius=((.75/pi)*mass/density)^(1/3)
      mass=7.5*mass of earth
      density=2kg/liter (twice that of water)

      acceleration due to gravity=Gravitational constant*Mass of planet/(radius)^2

      thus, plug this into google=
      (Gravitational constant)*(7.5*mass of the earth)/((7.5*mass of the earth)/(2kg/liter)*.75/pi)^(2/3)

      google gives us: 9.7764354 m / s^2

      Yay!
      Now, we just need a breathable atmosphere! And light-speed spaceships (or faster)!

  4. Good news by KingPin27 · · Score: 5, Funny

    "could even be covered by a large and deep ocean â" it is the first serious "water world" candidate" .. Good.. I wonder if we can export Kevin Costner.

    --
    "i lost my dignity on a slippery wiener"
  5. Call me when we find an auric world. by Chris+Burke · · Score: 5, Funny

    Water worlds always have the crappiest minerals. Oh look more alkalines. Yay. It won't be worth spending the fuel to land on Gliese 581 d, much less the cargo hold space. Gliese 581 e might have iron and other metals, but being so close to the star it probably has major hot spots. So that's probably not worth landing on either until we meet the Melnorme and buy some tech off them.

    Oh well. Eliminating planets to explore is good too. There's a lot of stars in the sky, you know, and only so much time to explore them before the UrQuan return.

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    The enemies of Democracy are
    1. Re:Call me when we find an auric world. by Kell+Bengal · · Score: 4, Funny

      We should check out Vega. Maybe we'll find something interesting.

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    2. Re:Call me when we find an auric world. by Quothz · · Score: 4, Funny

      We should check out Vega.

      No. What happens on Vega, stays on Vega.

  6. Wanna see more: Celestia by SalaSSin · · Score: 5, Informative

    If you would like to know more, download Celestia, an open source project to cruise around the universe in 3D.
    Just select "go to object" and type in "gliese 581", you'll get the orbits of the different planets already found too.

    The neat thing is, you can just "cruise" around, speed up time to see how stellar objects move, and so on... Quite cool :-)

    --
    Any sufficiently advanced incompetence is indistinguishable from malice - Grey's Law
  7. Re:Let's blow this popsicle stand by Chris+Burke · · Score: 4, Funny

    As in Moonraker, we send the sexy geniuses first, right? Or do we send the Telephone Sanitizers and hairdressers, like in HHGG?

    Well according to the travel register, you're booked on the first flight! Take that however you want.

    --

    The enemies of Democracy are
  8. Re:Extraterrestial life by furby076 · · Score: 4, Insightful

    To state banally, once again it appears that Earth isn't the center of the Universe, or even an extraordinary spot. Sadly, mankind won't be ever capable of communicating with such a distant places. However, speculation about extraterrestrial life isn't pointless. In range of our capabilities and, moreover, not forbidden by limiting condition on light speed, is a spectroscopic measurement of atmospheres belonging to planets beyond the solar system. Thus, in principle probable, it would be a great achievement to find traces of organic matter.

    Those are some bold statements: 1) Considering how many planets we have looked at and that we can't find life on any of them this makes Earth very extraordinary.
    2) Not ever be able to communicate with distant places? You don't know what we will invent in the future. It may come out tomorrow, or it may come out in 300 years - but to say "never".
    3) Speculation about other life is not pointless - it feeds our soul and imagination to wonder if there is something else. If humans thought exploring was pointless we would still be living in Africa, definitely never have crossed the ocean, let alone landed on the moon (something that people, 100 years ago, thought was impossible)

    Finding organic material will be hard short of landing on the surface. We couldn't even do searches of Mars without sending a robotic device there, and even then it may miss something. It's hard, and may not get done in our lifetime (thought it might) but it is certainly not pointless or impossible, and considering how rare life is we should consider ourselves (and our planet) to be very rare and special, though hopefully not unique.

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    I do not support "The Man". I also do not support your irrational stupidity
  9. Re:Did any one else read that as... by 4D6963 · · Score: 3, Informative

    On the tinyurl site you can choose to have a preview page that shows you the actual url when you click on one of their link (storing the preference as a cookie iirc).

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  10. Everything except orbit and mass is speculation by Morgaine · · Score: 4, Interesting

    The science of extra-solar planet detection is very interesting, but speculation about surface conditions that might exist doesn't reflect the science at all, it's just fodder for the media and bloggers.

    The only things we know are extremely rough estimates of orbital parameters and mass, although the host star is well characterised. The speculation is conjuring up quite specific images in people's minds, and while fun, they're not justified. It's leading people without an astronomy background astray.

    --
    "The question of whether machines can think is no more interesting than [] whether submarines can swim" - Dijkstra
  11. Re:Extraterrestial life by Domint · · Score: 3, Interesting

    1) Considering how many planets we have looked at and that we can't find life on any of them this makes Earth very extraordinary.

    The only reason we are able to detect life on Earth is due to proximity - so you're just as guilty of jumping to conclusions as the GP. We've found planets that differ wildly from Earth because the easiest planets to detect are the fuck-all-huge ones. Just because we haven't observed Earth-like planets yet does not mean they aren't all over the bloody place. They're just rather hard to spot with current technologies.

  12. Re:Strange biology by confused+one · · Score: 3, Informative

    It's a red dwarf, not a white dwarf. Red dwarfs could be thought of as small low-energy stars. They're more numerous and last longer than Sun-like stars. It's a gimme -- because it's nearby, less massive, and produces less light, it's easier to see stuff around it.

  13. Re:Extraterrestial life by nizo · · Score: 5, Funny

    I think it would be a good idea to send a rocket with a screen and dvd player or something, with a big red button on it that plays it.

    Yeah, because if a big thing from another planet lands and I look inside and see a big red button attached to some unknown device, I'm gonna just press that puppy right away :-)

  14. Re:Did any one else read that as... by 4D6963 · · Score: 3, Informative
    --
    You just got troll'd!
  15. Re:Extraterrestial life by mangu · · Score: 3, Interesting

    Finding organic material will be hard short of landing on the surface

    If we do an absorption spectrum reading of the atmosphere, which can be done at astronomical distances, and find free oxygen that would be a strong evidence for life on that planet. Oxygen is so reactive that it wouldn't exist very long in a planet's atmosphere before combining with something, unless here is a process like life to replenish it.