Rocky Earth-Sized Exoplanet Found, Maybe Water-Bearing?

[Duckie]

Smallest Exoplanet Yet

COROT discovers smallest exoplanet yet, with a surface to walk on

3 February 2009
COROT has found the smallest terrestrial planet ever detected outside the Solar System. The amazing planet is less than twice the size of Earth and orbits a Sun-like star. Its temperature is so high that it is possibly covered in lava or water vapour.

About 330 exoplanets have been discovered so far, most of which are gas giants with characteristics similar to Jupiter and Neptune.

The new find, COROT-Exo-7b, is different: its diameter is less than twice that of Earth and it orbits its star once every 20 hours. It is located very close to its parent star, and has a high temperature, between 1000 and 1500°C. Astronomers detected the new planet as it transited its parent star, dimming the light from the star as it passed in front of it.

The density of the planet is still under investigation: it may be rocky like Earth and covered in liquid lava. It may also belong to a class of planets that are thought to be made up of water and rock in almost equal amounts. Given the high temperatures measured, the planet would be a very hot and humid place.

“Finding such a small planet was not a complete surprise”, said Daniel Rouan, researcher at the Observatoire de Paris Lesia, who coordinates the project with Alain Léger, from Institut d’Astrophysique Spatiale (Paris, France). “COROT-Exo-7b belongs to a class of objects whose existence had been predicted for some time. COROT was designed precisely in the hope of discovering some of these objects,” he added.

Very few exoplanets found so far have a mass comparable to Earth’s and the other terrestrial planets: Venus, Mars, and Mercury. This is because terrestrial planets are extremely difficult to detect. Most of the methods used so far are indirect and sensitive to the mass of the planet, while COROT can directly measure the size of its surface, which is an advantage. In addition, its location in space allows for longer periods of uninterrupted observation than from ground.

“For the first time, we have unambiguously detected a planet that is 'rocky' in the same sense as our own Earth.”

This discovery is significant because recent measurements have indicated the existence of planets of small masses but their size remained undetermined until now.

The internal structure of COROT-exo-7b particularly puzzles scientists; they are unsure whether it is an ‘ocean planet’, a kind of planet whose existence has never been proved so far. In theory, such planets would initially be covered partially in ice and they would later drift towards their star, with the ice melting to cover it in liquid.

"This discovery is a very important step on the road to understanding the formation and evolution of our planet," said Malcolm Fridlund, ESA’s COROT Project Scientist. “For the first time, we have unambiguously detected a planet that is 'rocky' in the same sense as our own Earth. We now have to understand this object further to put it into context, and continue our search for smaller, more Earth-like objects with COROT," he added.

Needless to say, this is very awesome. Such a planet would probably be the best possibility to find life short of Europa- and the best for extrasolar life definitely. I don't get how it can be water bearing like they're theorizing if it's 1500 degrees celsius there. Did they mess up the temperature scale? Unless maybe it has water when it's far away (how) but it boils off when close?

[Sky Captain]

How can there be water vapor or even any kind of atmosphere so close to the star? I`d expect intense radiation coming from star would quickly brake apart water and strip atmosphere away and turn whole planet into glowing ball of magma.

[Tahlan]

The advances in the technology of astronomy boggle my diminutive mind. When I grow up I want to be an astrophysicist. Amazing stuff.

[Duckie]

Ah, I see- they're theorizing it's a planet which was once an iceball which has drifted in closer to the star (perhaps by impact hitting it closer) and thus is covered in steam and/or lava.

[GrandMasterTerwynn]

Needless to say, this is very awesome. Such a planet would probably be the best possibility to find life short of Europa- and the best for extrasolar life definitely.

At fifteen-hundred degrees centigrade, the planet is just a bit too hot to support life of any sort. Also, ESA's article title is misleading, as it's not the smallest exoplanet found. For example, Gliese 876d has a mass of 5.9 to 7.5 Earths, whereas COROT-Exo-7b has a mass between 7.5 to 11 Earths. What it is, is the smallest exoplanet discovered via the transit method.

I don't get how it can be water bearing like they're theorizing if it's 1500 degrees celsius there. Did they mess up the temperature scale? Unless maybe it has water when it's far away (how) but it boils off when close?

The article states the planet may have formed further out, and then migrated inwards to its present location. It's also quite a bit more massive than Earth, and would be better able to hold onto a deep atmosphere of water vapor. So it may be water-bearing in much the same way a high-pressure steam line is water-bearing.

How can there be water vapor or even any kind of atmosphere so close to the star? I`d expect intense radiation coming from star would quickly brake apart water and strip atmosphere away and turn whole planet into glowing ball of magma.

See above. Also, the parent star is only 1.1 billion years old, meaning the star probably hasn't had enough time to strip the planet of its volatiles.

[Solauren]

Still, an impressive find given the size of the object.

This gives me hope we'll star finding Earth-like worlds in the 'Goldie Locks' zones in other solar systems.

[Duckie]

Needless to say, this is very awesome. Such a planet would probably be the best possibility to find life short of Europa- and the best for extrasolar life definitely.

At fifteen-hundred degrees centigrade, the planet is just a bit too hot to support life of any sort.

Yeah, I know, I was confused by the "may have water vapour" and "may be an ocean planet" parts and missed the temperature reading on my first post. I corrected myself in the second implicitly with "it is made of steam and lava". A mod can fixed to be "Used to be Water Bearing?" or just delete the water bit if they so like.

Although life is pretty weird, I wouldn't count life out of anywhere. Every time we look we're finding out some kind of life is alive in a stupid place where you wouldn't believe anything would be alive. I'm waiting for gas giant flyers, sun dragons, and now lava-steam-planet-swimmers any day now.

[spikenigma]

makes me wonder what the Kepler mission will find when it launches later this year

http://en.wikipedia.org/wiki/Kepler_Mission

[Grandmaster Jogurt]

At that temperature, if there's enough water there for >218atm of pressure, we could have supercritical water instead of just vapor. Not conducive to life as we know it, but it could still be accurate to call it an "ocean planet" if it's covered in the fluid.

[GrandMasterTerwynn]

At that temperature, if there's enough water there for >218atm of pressure, we could have supercritical water instead of just vapor. Not conducive to life as we know it, but it could still be accurate to call it an "ocean planet" if it's covered in the fluid.

I don't think you could call it an "ocean planet." You might call it a "water giant," perhaps? I mean, one could envision the planet having an atmosphere principally comprised of oxygen and water vapor, and the deeper you go, the higher the pressure, until you hit that supercritical pressure, and then you have supercritical water until you hit the planet's molten rocky innards. It'd be mostly like a gas giant, only with water, instead of hydrogen, and with a much bigger (but still unreachable and unlandable-upon) rocky core.

[Junghalli]

This gives me hope we'll star finding Earth-like worlds in the 'Goldie Locks' zones in other solar systems.

I believe the Kepler Mission is supposed to be able to do that, which makes me very excited about it. Of course, for a planet in an Earth-like orbit, it would be a couple of years before they could confirm it.

[GrandMasterTerwynn]

This gives me hope we'll star finding Earth-like worlds in the 'Goldie Locks' zones in other solar systems.

I believe the Kepler Mission is supposed to be able to do that, which makes me very excited about it. Of course, for a planet in an Earth-like orbit, it would be a couple of years before they could confirm it.

Yes, Kepler is supposed to be able to spot planets in long-period orbits. It's supposed to do it via the transit method, which was how COROT-Exo-7b was discovered. What we really need to spot and quantify potentially habitable extrasolar planets in a reasonable timeframe is a sufficiently large telescope with adequate equipment (NASA's proposed New Worlds Mission,) or an interferometer (NASA's late, lamented Terrestrial Planet Finder, and ESA's proposed Darwin mission.)