Earth-sized planet found in Proxima Centauri's habitable zone

[Captain Seafort]

The nearest habitable world beyond our Solar System might be right on our doorstep - astronomically speaking.

Scientists say their investigations of the closest star, Proxima Centauri, show it to have an Earth-sized planet orbiting about it.

What is more, this rocky globe is moving in a zone that would make liquid water on its surface a possibility.

Proxima is 40 trillion km away and would take a spacecraft using current technology thousands of years to reach.

Nonetheless, the discovery of a planet potentially favourable to life in our cosmic neighbourhood is likely to fire the imagination.

"For sure, to go there right now is science fiction, but people are thinking about it and it's no longer just an academic exercise to imagine we could send a probe there one day," said Guillem Anglada-Escudé whose "Pale Red Dot" team reports the existence of the new world in the journal Nature.

Earlier this year, the billionaire venture capitalist Yuri Milner said he was investing $100m in studies to develop tiny spacecraft that could be propelled across the galaxy by lasers.

These would travel at perhaps 20% of the speed of light, shortening the journey to a star like Proxima Centauri to mere decades.

Just how "habitable" this particular planet really is, one has to say is pure speculation for the time being.

The Queen Mary University of London researcher and his group concede they still have much work to do to extend their observations.

Simply identifying the world, catalogued as "Proxima b", was a considerable challenge.

It was made possible through the use of an ultra-precise instrument called HARPS.

This spectrograph, attached to a 3.6m telescope in Chile, detects the very slight wobble induced in a star when circled by a gravitationally bound planet.

Its data suggests Proxima b has a minimum mass 1.3 times that of Earth and orbits at a distance of about 7.5 million km from the star, taking 11.2 days to complete one revolution.

The distance between the star and its planet is considerably smaller than Earth's separation from the Sun (149 million km). But Proxima Centauri is what is termed a red dwarf star. It is much reduced in size and dimmer compared with our Sun, and so a planet can be nearer and still enjoy conditions that are potentially as benign as those on Earth.

"This planet is at 5% of the Earth's distance from the Sun. However, Proxima is 1,000 times fainter than the Sun. So the flux - the energy - reaching Proxima b is about 70% of what the Earth receives. It's like taking Earth a bit further away, but it's comparable," explained Dr Anglada-Escudé.

Whether the temperatures on Proxima b are favourable for life to exist is going to depend on the presence of an atmosphere.

An envelope of greenhouse gases would warm surface conditions and provide sufficient pressure to keep water - essential for biology - in a liquid state.

But even with the limited information we currently have, scientists are excited by the news.

"I think it's the most important exoplanet discovery there will ever be - how can you ever trump something that could be habitable orbiting around the very closest star to the Sun?" commented Dr Carole Haswell from the Open University.

"When I was a kid, it wasn't clear there were any other planets that we could walk around on and find liquid water on - so I think it's absolutely thrilling," she told BBC News.

Researchers are presently looking to see if the planet crosses the face of Proxima Centauri as viewed from Earth - an event referred to as a "transit".

This kind of backlit observation could confirm not just the existence of an atmosphere but reveal perhaps something of its chemical properties.

Indeed, researchers have long talked about using transits to try to detect the signatures of life on planets that are too far away to be visited by spacecraft.

If there are lifeforms on Proxima b - even simple microbes - they may find the going rather tough, however.

Red dwarfs are very active. They tend to throw out big flares that would bombard a nearby planet with energetic particles. The X-ray emission is much more intense as well.

Even so, these kinds of stars are now the subject of great interest in the search for Earth-like planets simply because they are so abundant in the galaxy.

One priority for the future will be to get a direct image of the planet.

This should be possible with the European Extremely Large Telescope now under construction in Chile.

It is being given a 39m-wide primary mirror and state-of-the-art instrumentation precisely to do this kind of observation.

"A planet around even a wimpy star like Proxima Centauri is going to be more than a billion times fainter than the star itself. So, what you do is block out the light from the star using a special device and that allows you then to go deeper into the star's surroundings," explained Cambridge University's Prof Gerry Gilmore.

"This is one of the E-ELT's design goals. There's also a Nasa mission under development called W-First. It will have a high-resolution chronographic mode which again is designed for the same purpose."

Beeb

[U.P. Cinnabar]

Proxima III? Somebody better alert Earthforce!

[Borgholio]

This is cool. It's close enough we could potentially get some images of it with a big enough telescope.

[The Romulan Republic]

More importantly, in the long term, its an Earth-sized, possibly even Earth-like, planet close enough that we might be able to reach it someday.

[Simon_Jester]

Uh... the telescope would have to be really big.

Put this way. The planet "Proxima b" is about ten thousand times farther away than Pluto. With the Hubble Space Telescope in Earth orbit, Pluto looks like this:

http://www.nasa.gov/images/content/4215 ... y-full.jpg

The planet is three pixels wide in the Hubble's field of view; it took a lot of image processing to get that much imagery out of such limited data.

Contrasting Hubble pictures with what Pluto really looks like:



[Note that this actually understates the case, because the image I just put in my post has less pixels than the actual New Horizons picture of Pluto, and is therefore blurrier than it should be]

So we can see that even to get the most pathetically blurry pictures of a planet ten thousand times farther away than Pluto, we will need a telescope roughly ten thousand times superior to the Hubble. This is doable, but would be a very large and extensive undertaking- though, again, a very much possible one. And quite possibly cheaper than sending even a tiny probe to observe Proxima b directly.

[GrandMasterTerwynn]

It's close enough that we could possibly visit it inside a human lifetime (it's four decades away at 10% of the speed of light) with another, say, hundred years of technological development. Not that there's going to be much to look at once we get there ... given that it's certainly tidally locked, its slow rotation would make for a fairly weak magnetic field. Since Proxima Centauri, being a flare star, would randomly shower the planet with flares whose radiation intensity would be about 400x what we experience on Earth ... the planet's atmosphere is likely to be Mars-like (or Mercury-like, even), as successive flares scour it away (and Proxima Centauri is a couple hundred million years older than Sol ... so this process would've had a long time to occur.)

Still, in some of the stories I've read, it sounds like there are a handful of simulation models that would produce a planet inside Proxima Centauri's habitable zone with a thick atmosphere. The way that scenario plays out is that the planet forms much further out and winds up migrating inward to its current location. That way, it misses out on the more active days of Proxima Centauri's youth, and comes in with a stronger magnetic field. If it formed at, or close to it's current position; then it tidally locks early on and the big flares do the rest.

Still, where there are rocky planets, there are likely asteroids and comets to be had ... so the existence of Proxima Centauri's putative super-Mars makes the system much more desirable real-estate. Especially since Proxima Centauri will remain on the main sequence for some four trillion years ...

[Simon_Jester]

Also, if Proxima Centauri is desirable real estate capable of supporting a space-based civilization, the planet may be terraformable (should the locals choose to make the effort). Especially with space-based infrastructure like sunshades and orbital mirrors to create some semblance of a normal day-night cycle and to provide shielding against radiation.

[Eternal_Freedom]

From what the OP article said, the 39m E-ELT currently building in Chile should be able to image this planet. I guess whatever they had planned for their first observing run just got bumped.

[Borgholio]

Uh... the telescope would have to be really big.

Put this way. The planet "Proxima b" is about ten thousand times farther away than Pluto. With the Hubble Space Telescope in Earth orbit, Pluto looks like this:

http://www.nasa.gov/images/content/4215 ... y-full.jpg

The planet is three pixels wide in the Hubble's field of view; it took a lot of image processing to get that much imagery out of such limited data.

Contrasting Hubble pictures with what Pluto really looks like:



[Note that this actually understates the case, because the image I just put in my post has less pixels than the actual New Horizons picture of Pluto, and is therefore blurrier than it should be]

So we can see that even to get the most pathetically blurry pictures of a planet ten thousand times farther away than Pluto, we will need a telescope roughly ten thousand times superior to the Hubble. This is doable, but would be a very large and extensive undertaking- though, again, a very much possible one. And quite possibly cheaper than sending even a tiny probe to observe Proxima b directly.

Well yeah I'm not saying we can take a peek at it and see naked aliens sunbathing. It is definitely possible with current tech, however, to view light from the planet and get spectrographic readings of the planet and it's atmosphere (if it has one).

[SpottedKitty]

An intriguing side-note to this, which I don't think any news reports have picked up on yet, is that if two stars as close as our Sun and Proxima have confirmed planets... hold on...

<stamps foot on ground> Yep, confirmed.

... then the likelihood of any random star having planets has to go up. Time to try plugging new numbers into the Drake Equation, maybe?

And something else; can anyone remember if there have been other systems discovered around a red dwarf? That would also increase the different types of star that can have planets. Of course, there's the issue of heavy stars burning out so quickly they fall off the Main Sequence before any planets have time to form, but yellow and red dwarf stars like our Sun and Proxima are a lot more common.

Interesting days...

[Borgholio]

It was always theorized that dwarf stars (red, orange, yellow) had the highest probability of planets due to the fact that dwarf stars last much longer than the bigger ones, and because they tend to have more stable output than the big giants. The cruel twist is though, that due to their size, it has always been much harder to find said planets. But now that we know of two dwarf stars that have confirmed planets (Sol is a yellow dwarf, didn't ya know?), I agree with SK that the Drake Equation just got boosted by an order of magnitude.

[Guardsman Bass]

Sky and Telescope is saying the X-Ray influx would "only" be 100 times what Earth gets, revised down from 400 times. Other than that the rest of the potential issues with the planet hold true, from atmosphere stripping to the pre-main sequence problem (red dwarf stars are more luminous in their extended pre-main sequence phase, meaning this planet might have had a runaway greenhouse effect even if it hasn't lost its atmosphere).

That said, it could still have life even if Proxima has stripped away most of its atmosphere. It'd be like a giant version of Mars, with life underground as a remnant from more habitable days (like the deep biosphere on Earth).

I'm still pretty pessimistic about the habitability of red dwarf systems, although the sheer number of them means they could be significantly less likely to produce habitable planets than F-G-K stars and still produce tons of earth-like planets. If we do find an earth-like planet around one of them, it will probably be around one of the larger M-class stars (I've read that they tend to be quieter the bigger they are in terms of flares).

[Borgholio]

At least the planet would be a somewhat comfortable temperature. You wouldn't need a spacesuit or Arctic weather gear to walk around, just an oxygen mask and a lead-lined umbrella.

[EnterpriseSovereign]

I found it hilarious that some of those interviewed said that because Sol will run out of fuel someday, Proxima might become a viable alternative. They seem to forget that the Earth will be habitable for billions of years yet- so while the trip would take thousands of years at today's capabilities, Humanity will be unimaginably more advanced by that time*. Thus moving the Earth further from the sun to keep it habitable would be no less viable than a planetary evacuation.

*Assuming Humanity hasn't gone extinct by then.

[Simon_Jester]

One should not think so much in terms of evacuating the planet as in terms of ensuring that there are places for humans to live that can gracefully outlast the Sun burning out.

[Eternal_Freedom]

I found it hilarious that some of those interviewed said that because Sol will run out of fuel someday, Proxima might become a viable alternative. They seem to forget that the Earth will be habitable for billions of years yet- so while the trip would take thousands of years at today's capabilities, Humanity will be unimaginably more advanced by that time*. Thus moving the Earth further from the sun to keep it habitable would be no less viable than a planetary evacuation.

*Assuming Humanity hasn't gone extinct by then.

I now have a bizarre desire to work out how much delta-V would be required to move Earth in a transfer orbit to Proxima Centauri. I'm betting the numbers are quite literally astronomical.

[Borgholio]

I'm betting the numbers are quite literally astronomical.

Nah. Should be a breeze.

[Eternal_Freedom]

On the plus side we could turn the entire planet and future of the human race into a super-sized Space: 1999 knockoff.

[Sea Skimmer]

I now have a bizarre desire to work out how much delta-V would be required to move Earth in a transfer orbit to Proxima Centauri. I'm betting the numbers are quite literally astronomical.

So the earth can spend thousands of years freezing as it travels through the void? Oh and our tides would stop so the ocean dies and the climate goes crazy even if you brought along a giant heat ray.

Seriously it'd be easier to build an earth like planet out of debris in the other system.

[Eternal_Freedom]

Frankly, if we do ever find a way to give Earth that much delta-V we would have to have such godlike ubertech that keeping tides going and keeping the atmosphere warm without a sun won't be beyond the realms of possibility.

[Simon_Jester]

I now have a bizarre desire to work out how much delta-V would be required to move Earth in a transfer orbit to Proxima Centauri. I'm betting the numbers are quite literally astronomical.

So the earth can spend thousands of years freezing as it travels through the void? Oh and our tides would stop so the ocean dies and the climate goes crazy even if you brought along a giant heat ray.

Hey, if you can move the Earth, you can bring along the moon for a 2% or lower surcharge in energy budget.

[Solauren]

Heck, bring the rest of the planets! Let's just move the solar system!


But, seriously, interesting somewhat exciting news.

I'd be more excited if it was around a yellow dwarf. Red Dwarfs, has mentioned, make life less likely.

[Rhadamantus]

Fuck.
Right. This means that habitable planets are around 10% of star systems. If that's true, then there should be tens of billions of habitable planets in the galaxy. Since life seems commons, there should be billions of civilizations that have existed, and hundreds of thousands around now. There aren't. Therefore, either we can't find them, life is difficult, or intelligent life exterminates itself easily.

[Broomstick]

Or life is common, but intelligent life is rare.

[The Romulan Republic]

Fuck.
Right. This means that habitable planets are around 10% of star systems. If that's true, then there should be tens of billions of habitable planets in the galaxy. Since life seems commons, there should be billions of civilizations that have existed, and hundreds of thousands around now. There aren't. Therefore, either we can't find them, life is difficult, or intelligent life exterminates itself easily.

An intelligent species that didn't build anything we could detect with radio telescopes could be sitting around Proxima Centauri and be utterly unknown to us.