Scientists find potentially habitable planet.

Scientists find potentially habitable planet.

Postby JudgeKing » Thu Sep 30, 2010 10:02 am

New planet discovered orbiting Gliese 581

To astronomers, a "potentially habitable" planet is one that could sustain life, not necessarily one that humans would consider a nice place to live. Habitability depends on many factors, but liquid water and an atmosphere are among the most important.

"Our findings offer a very compelling case for a potentially habitable planet," said Steven Vogt, professor of astronomy and astrophysics at UC Santa Cruz. "The fact that we were able to detect this planet so quickly and so nearby tells us that planets like this must be really common."

The findings are based on 11 years of observations at the W. M. Keck Observatory in Hawaii. "Advanced techniques combined with old-fashioned ground-based telescopes continue to lead the exoplanet revolution," said Paul Butler of the Carnegie Institution. "Our ability to find potentially habitable worlds is now limited only by our telescope time."

Vogt and Butler lead the Lick-Carnegie Exoplanet Survey. The team's new findings are reported in a paper to be published in the Astrophysical Journal and posted online at arXiv.org. Coauthors include associate research scientist Eugenio Rivera of UC Santa Cruz; associate astronomer Nader Haghighipour of the University of Hawaii-Manoa; and research scientists Gregory Henry and Michael Williamson of Tennessee State University.

The paper reports the discovery of two new planets around the nearby red dwarf star Gliese 581. This brings the total number of known planets around this star to six, the most yet discovered in a planetary system other than our own solar system. Like our solar system, the planets around Gliese 581 have nearly circular orbits.

The most interesting of the two new planets is Gliese 581g, with a mass three to four times that of the Earth and an orbital period of just under 37 days. Its mass indicates that it is probably a rocky planet with a definite surface and that it has enough gravity to hold on to an atmosphere, according to Vogt.

Gliese 581, located 20 light years away from Earth in the constellation Libra, has a somewhat checkered history of habitable-planet claims. Two previously detected planets in the system lie at the edges of the habitable zone, one on the hot side (planet c) and one on the cold side (planet d). While some astronomers still think planet d may be habitable if it has a thick atmosphere with a strong greenhouse effect to warm it up, others are skeptical. The newly discovered planet g, however, lies right in the middle of the habitable zone.

"We had planets on both sides of the habitable zone--one too hot and one too cold--and now we have one in the middle that's just right," Vogt said.

The planet is tidally locked to the star, meaning that one side is always facing the star and basking in perpetual daylight, while the side facing away from the star is in perpetual darkness. One effect of this is to stabilize the planet's surface climates, according to Vogt. The most habitable zone on the planet's surface would be the line between shadow and light (known as the "terminator"), with surface temperatures decreasing toward the dark side and increasing toward the light side.

"Any emerging life forms would have a wide range of stable climates to choose from and to evolve around, depending on their longitude," Vogt said.

The researchers estimate that the average surface temperature of the planet is between -24 and 10 degrees Fahrenheit (-31 to -12 degrees Celsius). Actual temperatures would range from blazing hot on the side facing the star to freezing cold on the dark side.

If Gliese 581g has a rocky composition similar to the Earth's, its diameter would be about 1.2 to 1.4 times that of the Earth. The surface gravity would be about the same or slightly higher than Earth's, so that a person could easily walk upright on the planet, Vogt said.

The new findings are based on 11 years of observations of Gliese 581 using the HIRES spectrometer (designed by Vogt) on the Keck I Telescope at the W. M. Keck Observatory in Hawaii. The spectrometer allows precise measurements of a star's radial velocity (its motion along the line of sight from Earth), which can reveal the presence of planets. The gravitational tug of an orbiting planet causes periodic changes in the radial velocity of the host star. Multiple planets induce complex wobbles in the star's motion, and astronomers use sophisticated analyses to detect planets and determine their orbits and masses.

"It's really hard to detect a planet like this," Vogt said. "Every time we measure the radial velocity, that's an evening on the telescope, and it took more than 200 observations with a precision of about 1.6 meters per second to detect this planet."

To get that many radial velocity measurements (238 in total), Vogt's team combined their HIRES observations with published data from another group led by the Geneva Observatory (HARPS, the High Accuracy Radial velocity Planetary Search project).

In addition to the radial velocity observations, coauthors Henry and Williamson made precise night-to-night brightness measurements of the star with one of Tennessee State University's robotic telescopes. "Our brightness measurements verify that the radial velocity variations are caused by the new orbiting planet and not by any process within the star itself," Henry said.

The researchers also explored the implications of this discovery with respect to the number of stars that are likely to have at least one potentially habitable planet. Given the relatively small number of stars that have been carefully monitored by planet hunters, this discovery has come surprisingly soon.

"If these are rare, we shouldn't have found one so quickly and so nearby," Vogt said. "The number of systems with potentially habitable planets is probably on the order of 10 or 20 percent, and when you multiply that by the hundreds of billions of stars in the Milky Way, that's a large number. There could be tens of billions of these systems in our galaxy."


Provided by University of California - Santa Cruz



This is very interesting to hear, though its kind of a shame that the planet is tidally locked.
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Re: Scientists find potentially habitable planet.

Postby SolkaTruesilver » Thu Sep 30, 2010 12:36 pm

This is the kind of discovery that makes you realise just how specially unique Earth is...

I say we can't take the chance of a rival specie out-tech-ing us. We should launch the nukes against that planet, just in case.
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Re: Scientists find potentially habitable planet.

Postby Tyyr » Thu Sep 30, 2010 12:42 pm

Given the very small number of small rocky planets discovered so far due to technology limits I think it's a bit early to jump to the conclusion that Earth is a beautiful and unique snowflake.
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Re: Scientists find potentially habitable planet.

Postby SolkaTruesilver » Thu Sep 30, 2010 1:03 pm

Well, since only one in X stars isn't a dangerous radiation-spawing horror

Only one in Z have a solar system at all

Since only one in Y of those solar system have solid planets

And only one in ? of those planets is actually in the right range (only 1 discovered so far)

Only one in ??? has the right gravitational scheme

It starts to be quite rare. Off course, it also means there could be millions of such planet in our galaxy alone, but it still rates as "rarer than a sober irishman not drinking the pint of lager he carries through Mecca" rare.
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Re: Scientists find potentially habitable planet.

Postby Mikey » Thu Sep 30, 2010 1:38 pm

As Tyyr said, there's really no way to tell how rare this type of rocky planet is... the radial spectometry used is an iffy science at best, and thus far can only indirectly detect the presence f such planets. The fact that we haven't found many so far only indicates the fact that we don't really know how to find them very efficiently. It may turn out, when we get better at looking for them, that such planets may not be quite so rare, and that every single one holds an atmosphere.
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Re: Scientists find potentially habitable planet.

Postby SolkaTruesilver » Thu Sep 30, 2010 1:40 pm

Oh well

If they do find there is that many planets, I sure hope they break out the nukes. :poke:
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Re: Scientists find potentially habitable planet.

Postby Tyyr » Thu Sep 30, 2010 2:14 pm

Remember, we're finding rocky planets, but they're still 2 to 3 times more massive than Earth. If you look at our solar system Earth is the LARGEST rocky planet in it. So we're still picking out planets that are larger than any rocky planet we've seen.

Solar systems aren't that rare. We still aren't able to locate many small planets and yet we're still finding stars with multiple HUGE planets. Planets with 2 and 3 times the mass of Jupiter are getting down right common to find and given how much larger these planets are than ours are it stands to reason that there's a good chance that these stars may also be absolutely lousy with small terrestrial planets. We'll have to see as our instruments get better at picking out planets. We're continually finding smaller and smaller planets.

Lets look at it this way. There are about 100 Billion stars in our galaxy. Lets assume only one in a thousand of them have a solar system (probably stupidly low on that estimate) that still leaves us with a hundred million planetary systems. Now assume only one in a thousand of those has a rocky planet in the goldilocks zone. We could have 100,000 potential life bearing planets similar to Earth in this galaxy alone and the thing is, the one in a thousand odds on both those numbers is starting to look more and more like a titanic low balling.

Factor in that the universe has something like 100 billion galaxies in it just that we can see and the odds that we're in any way unique start to get really, really low.
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Re: Scientists find potentially habitable planet.

Postby USSEnterprise » Fri Oct 01, 2010 4:43 am

My astronomy knowledge is pretty much nothing, how do we look for planets in other solar systems? I assume it has something to do with gravity and star brightness? :confused:
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Re: Scientists find potentially habitable planet.

Postby shran » Fri Oct 01, 2010 11:14 am

yup. As a planet passes in fort of its star while we are observing it, small changes in the light emitted for the star occur in our viewpoint, because a small amount of said light is blocked or warped by the presence of the planet.
Also, as a planet makes it's orbit, it makes the star wobble ever so slightly with it's mass.
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Re: Scientists find potentially habitable planet.

Postby Mikey » Fri Oct 01, 2010 2:48 pm

Indeed, even in our own solar system the outermost planets were predicted by gravitational effect before they were actually discovered.
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Re: Scientists find potentially habitable planet.

Postby SolkaTruesilver » Fri Oct 01, 2010 3:23 pm

Mikey wrote:Indeed, even in our own solar system the outermost planets were predicted by gravitational effect before they were actually discovered.


The was still 1 planet that surprised some people, no? Neptune? Wasn't there a calculation about the time to go around the sun that, before Neptune, was very efficient? (maybe my memory is confused, too)

Pluto was more of an anomaly, as it was discovered but pure luck, and we have now established there is nothing unique about it. It lacks gravitational impact on it's sorrounding...
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