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."

Comments

but what about Earth 2...

[squoozer]

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.

Re:but what about Earth 2...

[Chris Burke]

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.

Re:Extraterrestial life

[furby076]

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.

Re:Extraterrestial life

[kegger64]

That's a 20-year round trip for radio communications, sure... but we are currently capable of communicating with "such a distant places" (sic). We have been for the better part of a half a century.

Radio communication was invented in 1960?

Re:Astronomy

[Kjella]

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.

Consider it a bit like breaking a world record, "closest to Earth" is a big title but ultimately you only need to beat the old record by an inch. The answer I'd say is "much, much closer than anything we've observed in the history of mankind and still very, very far away". There's so many variables you could tweak about size, distance from star, temperature, rotation time, composition, magnetic field, atmosphere, jupiter-type asteroid shields and whatnot. We're very far from saying whether anything we find is earth's twin or earth's distant halfcousin. Still, science is progressing at a wild pace, when I was a kid exoplanets was mere conjencture, something scientists had speculated about but never observed. The real joker in the equation is life, because well we know life exists on earth so without considering other exotic forms of life, our kind of life could exist on other earth-like planets. Or even just the realization that if we could get humans from this planet to that earth-like planet, we really could thrive on another planet, not just a bomb shelter on Mars - that'd be huge. We're getting closer and closer to that, but how exciting the steps are depends on your perspective.

Re:Extraterrestial life

[FrameRotBlues]

I think a lot of people would freak the fuck out if we sent them a bunch of information in English and they sent their responses in English.

I'd expect that any response would sound like static or gibberish, and we might not be able to decode it for a long time. As cheesy as some parts of "Contact" were, that part was probably about right: We receive their "message" and then spend months going, "WTF did they send us?"