National Geographic Daily News
An artist's illustration of the new planet, Kepler-186f.

This artist's depiction shows Kepler-186f, an Earth-size world in the "habitable zone" of a red dwarf star.

ILLUSTRATION BY NASA/JPL-Caltech/T. PYLE

Dan Vergano

National Geographic

Published April 17, 2014

Red sunshine, seas, and maybe aliens? Scientists analyzing data from NASA's Kepler Space Telescope today report the closest thing yet to another Earth, a world in a habitable orbit around a red dwarf star some 493 light-years away.

Launched in 2009 with the goal of finding another Earth, the $600-million Kepler spacecraft has discovered more than 960 planets orbiting nearby stars. Half a dozen of those seem to be rocky, like Earth, and have orbits in the habitable zone around their star—but the newly discovered world, named Kepler-186f, is the closest in size to Earth.

"This is a first, validated Earth-size planet in the habitable zone of another star," says study lead author Elisa Quintana of the SETI Institute and NASA's Ames Research Center in Mountain View, California. The discovery of the planet was reported today in the journal Science and in a space agency press briefing. (Related: "Motherlode of Alien Worlds Revealed by Space Telescope.")

One of five planets orbiting a red dwarf star (called Kepler 186), Kepler-186f is 1.1 times wider than Earth. That means it's almost certainly a rocky planet too. The researchers estimate its mass is 1.5 times that of Earth's.

The new planet's orbit, meanwhile, places it at the "Goldilocks" distance from its star—not too hot or too cold for liquid water to exist on its surface. The origin of life on Earth required liquid water, notes study co-author Stephen Kane of San Francisco State University.

"This is an historic discovery—the first Earth-size planet found in the habitable zone around its star," says pioneering planet hunter Geoff Marcy of the University of California, Berkeley, who was not on the discovery team. "This is the best case for a habitable planet yet found."

The planet's red dwarf star is only about half as big as the sun, making it cooler and dimmer. But Kepler-186f is on a tighter orbit than Earth is, taking only 130 days to circle its star. Though it receives less warmth from its sun than Earth does from its own, the discovery team says, it would still be warm enough to prevent seas from freezing—provided it has an atmosphere that provides a substantial greenhouse effect.

"This planet basks in an orange-red glow from that star, much as we enjoy at sunset," Marcy says, by email. "The temperature on the planet is likely cool, similar to dawn or dusk on a spring day."

Crowded Claims

"Sounds like a great planet to visit, if we could figure out how to travel there," says MIT astronomer Sarah Seager, by email. But amid the excitement, she and planetary scientist Alan Boss, author of The Crowded Universe: The Search for Living Planets, caution that other discoveries have led to similar claims in recent years.

Since 1995, astronomers have detected nearly 1,700 worlds orbiting nearby stars, using a variety of detection methods. About a half dozen claims of bigger Earth-size (or still larger "super-Earth") planets orbiting in habitable zones around red dwarfs have been made in recent years, Boss says. "Still, it once again proves what Kepler can do."

The next closest thing to Kepler-186f has a width 1.4 times that of Earth, Quintana says. According to Seager, a planet whose diameter is less than 1.75 Earths is likely to be rocky.

The Kepler report looks particularly reliable because of the spacecraft's track record. It detects planets that dim the light from their stars as they pass in front of them. Such transits, Quintana says, are observable only in the roughly one percent of planetary systems whose orbits can be seen edge on from Earth.

When transits occur regularly, their frequency allows scientists to calculate the distance at which a planet is orbiting a star. The amount of starlight dimming—typically on the order of 0.1 percent—is a measure of the planet's size.

Such searches are most sensitive to closer-in stars, because fewer days of observations are required to see repeated transits. That explains why the newly discovered planet's four closer-in siblings had been spotted earlier by the space telescope. "They relied on only two years of data," Quintana says. With so many planets in the system, it's likely to be stable over billions of years.

Tickets on Hold

Whether a life-friendly atmosphere exists on Kepler-186f depends on a bevy of factors besides having the right orbit. "We see planets in our own solar system—Venus but also Mars—that are Earthlike but where things didn't work out," Kane says.

On Venus, a runaway greenhouse climate has cooked the surface to temperatures that would melt lead. On Mars, the lack of a strong magnetic field has allowed the solar wind to strip away much of the planet's atmosphere. A magnetic field would be particularly important for a planet orbiting a red dwarf, because such stars tend to release strong flares that would sterilize the planet.

"Just because a planet is in the habitable zone doesn't mean it is habitable," Quintana says. "This is sort of a first step."

However, Kane argues that the greater mass of Kepler-186f makes it more likely than Mars to have an interior heated by radioactivity and stirred by the motion of fluids. Such motions are required to power a dynamo that generates a protective magnetic field as well as volcanoes, whose eruptions would help replenish a life-friendly atmosphere. The planet's mass would also give it enough gravity to hold on to that atmosphere.

"The other big question is whether it has water, delivered by comets or some other means," Kane says. "Any place with liquid water is a natural place to look for life."

Unfortunately, Kepler-186f is likely too dim and far away to be seen directly with any telescope now in operation, or even with NASA's James Webb Space Telescope, scheduled for launch in 2018.

"In reality we cannot know if the planet is actually habitable. We need to get a sense of the atmosphere and its greenhouse effect," Seager says. "Not possible for this particular planet, as it is too distant from Earth for follow-up observations."

Kepler's Chase

The latest Kepler discovery came from a trove of star observations that the spacecraft made before a reaction wheel in its steering system failed last year, hobbling the mission. A reduced "K2" mission was announced in March.

Hiding amid the existing Kepler observations, Kane says, are more unconfirmed "candidate" planets orbiting stars as big as the sun, at distances similar to Earth's 93-million-mile (150-million-kilometer) distance from the sun.

"There are still a lot more Kepler 'habitable zone' worlds out there to find," Kane says. "Almost certainly this is not the last one."

Follow Dan Vergano on Twitter.

173 comments
Brian Flikkema
Brian Flikkema

Possibly the first goldilocks planet found, most likely to contain life.  Has a rich atmosphere, just the right size, just the right zone.  On the news?  No, I had to read about it in GQ.  That would take to much of the news cycle dedicated to a missing plane that will never be found, Oscar Pistorius and famous people that nobody should actually care about.  But that's just me.

Antonio Siqueira
Antonio Siqueira

Earth, you are the most beautiful of the planets are mistreating you for money, then you think it is our nature, our home ... Earth, forgive us.

L. Jibuti
L. Jibuti

If we figure out how to reach a speed close to the speed of light we will be able to travel there and even come back within our lifetime without freezing yourself and things like that. However, there will be some side effects. For example, when we come back nothing will be there like we knew it. Earth will be at least about one millennium older.


At relativistic speeds due to the length contraction (from special relativity) distance will be shortened as much as we want (as much as we will be able to approach the speed of light). Theoretically we can reach there even in few seconds. 

However, even if we have necessary compact energy source we cannot travel such a distant places in few seconds because of that would requires a huge acceleration and we would not survive. 


But if we have enough energy which provides prescribed acceleration for out ship and we would choose our native one (g = 9.8 m/s2) we would need time ( t = v/g = 3*10^8 m/s / 10 m/s2 = 3*10^7 s = 3*10^7 / (60*60*24) days = 347 days). So,  we need about one year to reach the speed of light with the g acceleration which would feel like a home.  Then we need one year to slow down and land on the planet. 


So if we have enough energy we can go  to Kepler-186f and come back to Earth in about 4 years. But if we start now when we come back there on earth will be around  3008 A.C. ( 2014 + 2 + 493 + 2 +2 +493 + 2 = 3008 ).


In fact, this is how we can travel to future! :) Unfortunately, there is no theoretical mechanism to travel to past. 

Douglas Jackson
Douglas Jackson

Despite this planet being too far away to visit or study closely it is what we have been looking for: an earth-like planet. comparable to the Earth in size (and probably in density) that is at the right distance from its star. This is a great discovery. It suggests if we keep looking we will find a closer, more easily observed planet of this required type. If we keep investing in this line of inquiry and observe carefully, at this stage there is no reason to doubt that eventually - maybe tomorrow - we will see someone looking back.

MICHAL PAWLAK
MICHAL PAWLAK

Agreed. Technology is the key to advancing our knowledge of Earth-Like Worlds. However, how do we fund these expensive missions, when our economies can barely fund us?

T. Ray
T. Ray

Even though it's near an old red dwarf and that is our sun's future in a few million years, maybe a break through in tech will get us there before the extinction of humanity. I don't think catching a ride with a worm hole is our solution, yet. Keep working on the ION Drive people. 

Aster Assefa
Aster Assefa

ok this is good discovery however we have to discuss how could we travel there.I am going to present the idea to EU parliament to get financial help and with chinese government to produce the fastest spacecraft for our early arrival ,,,,,,,,,,,,,,,,,


gary childress
gary childress

My space ship will be completed once I figure out where the rest of these nuts go?

shum kwan
shum kwan

Maybe we can not travel to another world. As no other aliens can do it until now. It must have reasons. Maybe virus are million times strong at star edge or something exists to prevent our travel. Anyway I am happy to see a new world....

sc leong
sc leong

the god live there, that place is no way for human to reach, not by the existing science and technology! if one day human manage to discovered a way to travel that far, then human will become as one of the "God" too....   

Emmanuel Quizon
Emmanuel Quizon

If we have a spacecraft that can travel at 300,000 kilometers per second, our 5th centennial generation will reach there and probably forgot where they came from. Can there be a spacecraft that can travel at the speed of thought?

Miriam Stone
Miriam Stone

Hey - First possibly inhabitable planet!  It's a start!

DAVID WALLIS
DAVID WALLIS

we can only survive in about 12percent of our own environment which drops to 4percent if we include the oceans. If we include the atmospheres this leaves homo sapiens less than 1percent in volume of his own planet to live in - and we want to go into space where it is 100 times more hostile ?


john barbour
john barbour

I would need a toilet stop half way, too far for me to comprehend

MICHAEL AVALOS
MICHAEL AVALOS

No matter what I just love the science one day when we are able to go where our curiosity takes us , to learn and understand before we colonize or even co- exist with , we don't take our demons with us  , we have to evolve from our present stance on life before, we venture out there 

Ernest Doucette
Ernest Doucette

That is great news, but unless we find a way to fold space, or utilize a wormhole, at our present technology (even if we can push it with an ion drive to 100,000 miles per hour) it will take something like 24 million years to reach it!

Kip Keino
Kip Keino

The religionists are already cranking up their preachmobiles, hoping to be the first to get the aliens converted to their God.

Sanjay Chaurasia
Sanjay Chaurasia

It is a great discovery of science.Every body like to know about outer world phenomena and something new about cosmic world. We are also a creation of cosmic rays/ energy. We are affected by outer world too in a different ways. For example different stars provide us different kind of cosmic rays.By which our body get energy and atomic/molecular formation.

Jamil Ahmad
Jamil Ahmad

I am interested to know more about this newly discovered planet. I hope may be aliens  there ,but no  human beings.


Svetoslav Cvetanov
Svetoslav Cvetanov

Too much loss of space in the universe, if we are the only existing world ...

Anna Savelesky
Anna Savelesky

Aren't red dwarfs old; isn't that our sun's future in a few million years.  Therefore might red dwarf planets be past the stage of producing the possibility of life as we know.  Maybe their life forms died out at an earlier time or moved away. 

Neil Cubberley
Neil Cubberley

With literaly millions of planets and solar systems in the universe, it is very unlikely that there is not any life anywhere else but on our earth. Some will be further advanced than we are and some will be very primitive as we were a million years ago. But, until science finds a way to travel faster than light, we will never know for sure. 

will kari
will kari

There is no intelligent life on Earth ;therefore, no intelligent life in the universe. 

Richard Cleroux
Richard Cleroux

When was it proven that there is intelligent life in the universe?  I keep waiting for that proof.

Gary Ryckewaert
Gary Ryckewaert

We can not be the only intelligent life in the universe and for anyone to think so would be very arrogant. This story is incredibly interesting. I would love to be alive when either we find a habitable planet and have the technology to travel their or when other life finally finds us and drops by for coffee.

Scott Henry
Scott Henry

@MICHAL PAWLAK Stop all wars, and concentrate all of that money to finding a place to go when our star decides it's not going to support us any more.

joachim marthinus buys
joachim marthinus buys

@Kip Keino Religion is not a relationship to God and is therefore dead. To be a Christian mean to be in relationship to the father the Son and the Holly Spirit.

mark dixon
mark dixon

@Anna Savelesky  


Hi,


The next step in the evolution of our sun will be the red giant. The sun will have spent most of it's fuel and will expand enormously to try to keep working. Still 5 billion years in the future.

K C
K C

@Neil Cubberley


And considering our species has not evolved in a manner to travel "as fast as light" let alone "faster than".. Some things just aren't meant to be known.


It's still really fun to imagine. :)

K C
K C

@will kari  The funny thing about this statement (and I realize you're just being cynical) is that it would realistically require some form of 'intelligent life' in order to know the difference. There are most likely other life-forms out there that would consider our intelligence to be stupidity in comparison, and vice-versa.

The universe holds no bounds.

Emmanuel Quizon
Emmanuel Quizon

@Richard Cleroux  


Are you disproving your intelligence by insinuating that you are a moron? wake up! reasoning like that proves that you have intelligence!

Dave Nussbaumer
Dave Nussbaumer

@Gary Ryckewaert  

"other life finally finds us and drops by for coffee." Or dinner! :(

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