Found: one Earth-like planet - Astronomers use gravity lensing to spot homely planets.

news@nature.com ^ | 25 January 2006 | Mark Peplow

[neverdem]

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Published online: 25 January 2006; | doi:10.1038/news060123-5

Found: one Earth-like planet

Astronomers use gravity lensing to spot homely planets.

Mark Peplow

How to spot a planet: watch for wiggles in the light coming from a far distant star as it curves around another sun.© ESO

Astronomers say they have found the most Earth-like planet yet outside our Solar System. At just 5.5 times the mass of Earth it is one of the smallest extrasolar planets ever found, and orbits its star at a distance comparable to that of habitable worlds.

Similarly sized extrasolar planets have been found before. But the method used to detect them meant we could see smallish planets only when they were very close to their suns, and such bodies are battered by scorching radiation.

Planet OGLE-2005-BLG-390Lb looks much more like home. It lies about 390 million kilometres from its star: if it were inside our Solar System, the planet would sit between Mars and Jupiter.

It takes ten years for the planet to orbit its parent star, a common-or-garden red dwarf that lies about 28,000 light years from Earth, close to the centre of our Galaxy.

The search for a second Earth is the driving force behind our research.   Daniel Kubas at the European Southern Observatory in Santiago de Chile, Chile.

But sadly this Earth-like body probably isn't crawling with life. Its dwarf star is so dim that the surface temperature of this planet is thought to be about - 220 °C.

"The search for a second Earth is the driving force behind our research," says Daniel Kubas at the European Southern Observatory in Santiago de Chile, Chile, part of the team that made the discovery. They are optimistic that the clever method they used to spot the planet could soon uncover an alien twin to our own world.

Wobbly stars

More than 170 planets have been discovered outside our Solar System. Astronomers usually detect them by watching how they make their parent star wiggle, a technique known as the Doppler method. This is ideal if you are looking for massive planets orbiting very close to their star, which induce a lot of wobble.

But there is no way this can be used to find small, blue-green planets approximately 150 million kilometres from a yellow sun. It is simply not sensitive enough, says Didier Queloz, an astronomer from Geneva Observatory in Switzerland who was part of the team that found the first extrasolar planet, just 11 years ago¹.

The new sighting relies on an effect called gravitational lensing, where a massive object such as a star warps space so that it behaves like a lens. This means that it bends and slightly magnifies light from a more distant star before it reaches our telescopes. Adding a planet to the mix modifies the lensing effect by a tiny amount, just enough to work out its mass and orbit.

"Microlensing is the fastest way to find small, cool planets, down to the mass of the Earth," says Keith Horne, one of the planet's discoverers and an astronomer from the University of St Andrews, UK.

Spot the difference

The planet was found by a consortium of 73 astronomers from 12 different countries. Its star was first spotted by scientists working on the Optical Gravitational Lensing Experiment (OGLE), before the planet itself was noticed by astronomer Pascal Fouqué.

OGLE-2005-BLG-390Lb is only the third planet found using the microlensing technique so far, but astronomers expect to spot many more. "The other two microlensing planets have masses of a few times that of Jupiter, but the discovery of a five-Earth-mass planet is a strong hint that these objects are very common," says Jean-Philippe Beaulieu of the Astrophysics Institute of Paris. Beaulieu is lead author of the paper describing the find in this week's Nature².

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References

1. Mayor M.&

   Queloz D. . Nature, 378. 355 - 359 (1995). | Article | ISI | ChemPort |

2. Beaulieu J.P., et al. Nature, 439. 437 - 440 (2006). | Article |

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[Brett66]

I wish they wouldn't call these planets "Earthlike", it has no resemblence to the warm, ocean planet on which we live.

[skinkinthegrass]

sci. ping

[neverdem]

OK, where's the obligatory Helen Thomas pic. We have rules around here ya know...

What's that reason or rule? It's late and folks want to sleep.

[ChocChipCookie]

So would that make it an "M Class Planet"?

[neverdem]

So would that make it an "M Class Planet"?

Since at least Microsoft, Google and Yahoo are in cahoots with the Chicoms, why don't you Ask Jeeves and tell the rest of us? I only took one formal class in astronomy many moons ago.

[ChocChipCookie]

That was just a little Star Trek humor. I guess I've watched a few too many episodes. :O)

[Bogey78O]

We don't know the atmosphere yet it seems.

[steve-b]

We don't know the atmosphere yet it seems.

I'm not sure if anything other than hydrogen and helium are still gases at -220 C (53 K).

[edcoil]

"of habitable worlds."

Excuse me, other then earth where is there a habitable world?

[KevinDavis]

It seems like they are find smaller planets.. Maybe I should start a pool when we truly find a Earth like planet..

[NCC-1701]

Take it from me, you can NEVER watch too many Star Trek episodes.

[wyattearp]

Excuse me, other then earth where is there a habitable world?

That depends on what you mean by "habitable". If you mean walk around in jeans and a t-shirt and have an outdoor barbecue...

We haven't found any.

On the other hand, if you allow spacesuits and airtight habitat modules lots of places are habitable.

[wyattearp]

Also, what is -220 degrees C compared to Farenheit?

Fahrenheit is 9/5C + 32. So, that would make it a somewhat chilly -364 degrees F. Not exactly shirtsleeve weather.

[Heatseeker]

OGLE-2005-BLG-390Lb is only the third planet found using the microlensing technique so far, but astronomers expect to spot many more.

So that makes the name of the inhabitants of the planet OGLE-2005-BLG-390Lbians?

[Centurion2000]

I'm curious why a terrestrial planet massing 5.5 Earths wouldn't have retained it's H/He atmosphere and remained a gas giant. I bet this is a captured planet from a much hotter solar system.

[FierceDraka]

5.5 Earth masses, in a distant orbit from a red dwarf, and -220 C in summer?

Not exactly "homey", but we'll start finding nice nitro-oxy-hydro planets before long.

And hopefully figure out a way to get there and conquer them.

[FierceDraka]

28,000 light years is kind of far away; can't they find something closer-like, say, 20 or 30 light years?

Finding planets in the Alpha Centauri system would be nice. Seeing as it's a fairly tight binary system (unless you count Proxima), it's unlikely to have any massive, easily-detectable gas giants.

Still, any habitable or terraformable planets around Alpha Centauri A or B might be a little too close to Earth and its meddling UN for some colonists.

[spikeytx86]

I think America should declare the moon American property. We were there first. We have never really explored there, who knows what goodies could be under ground (never know it could have 100 trillion barrels of crude LOL.)

[FierceDraka]

I think America should declare the moon American property. We were there first. We have never really explored there, who knows what goodies could be under ground (never know it could have 100 trillion barrels of crude LOL.)

Possession is 9/10's of the law.

But I'm afraid there's no crude on the moon. Plenty of tasty H3 for fusion, though.

[SunkenCiv]

Thanks neverdem. I was wondering if I should post it, but I’d missed it before:

http://www.freerepublic.com/focus/f-bloggers/1607979/posts?page=110#110