Skip to main content

3 new planets could host life

By Elizabeth Landau, CNN
April 21, 2013 -- Updated 1248 GMT (2048 HKT)
This diagram lines up planets recently discovered by Kepler in terms of their sizes, compared to Earth. Kepler-22b was announced in December 2011; the three Super-Earths were announced April 18, 2013. All of them could potentially host life, but we do not yet know anything definitive about their compositions or atmosphere. This diagram lines up planets recently discovered by Kepler in terms of their sizes, compared to Earth. Kepler-22b was announced in December 2011; the three Super-Earths were announced April 18, 2013. All of them could potentially host life, but we do not yet know anything definitive about their compositions or atmosphere.
HIDE CAPTION
Where life might live beyond Earth
Where life might live beyond Earth
Where life might live beyond Earth
Where life might live beyond Earth
Where life might live beyond Earth
Where life might live beyond Earth
Where life might live beyond Earth
<<
<
1
2
3
4
5
6
7
>
>>
STORY HIGHLIGHTS
  • Scientists discovered 3 planets in the "habitable zone" of their host stars
  • Kepler-69c seems less clearly in the habitable zone than the other two planets
  • They are all more than 1,000 light-years away
  • The Kepler satellite is looking at more than 150,000 stars for possible planets orbiting them

(CNN) -- In the midst of chaos here on Earth, scientists are finding hope for life on other planets.

Scientists announced Thursday the discovery of three planets that are some of the best candidates so far for habitable worlds outside our own solar system -- and they're very far away.

NASA's Kepler satellite, which is keeping an eye on more than 150,000 stars in hopes of identifying Earth-like planets, found the trio.

Two of the planets -- Kepler-62e and Kepler-62f -- are described in a study released Thursday in the journal Science. They are part of a five-planet system in which the candidates for life are the farthest from the host star.

Their host star -- which corresponds to Earth's sun, but is smaller and cooler -- takes the name Kepler-62. The star's planets are designated by letters after the star's name.

A third planet that's potentially habitable, but not included in the Science study, is called Kepler-69c. A study about it and its system is published in The Astrophysical Journal.

These are the smallest planets ever found in the "habitable zone," the area near a star in which a planet can theoretically hold liquid water. Kepler-69c seems less clearly in the habitable zone than the other two planets, but scientists haven't ruled it out.

"With all of these discoveries we're finding, Earth is looking less and less like a special place and more like there's Earth-like things everywhere," said Thomas Barclay, Kepler scientist at the Bay Area Environmental Research Institute in Sonoma, California.

You won't be swimming on the planets anytime soon, though. The Kepler-62 star is 1,200 light-years away; Kepler-69 is 2,700 light-years away. A light-year, the distance that light travels in a vacuum in one year, is nearly 6 trillion miles.

What are these planets like?

The smaller a planet is, the more likely it's rocky and the less likely it's made of gas, said William Borucki, Kepler science principal investigator at NASA Ames Research Center.

That makes Kepler-62f, thought to be 40% larger than Earth, potentially the most like our planet out of the new discoveries. It could be rocky, Borucki said, with polar caps, land mass and water as well. It goes around its star once every 267.3 days (Earth days, that is).

If you were standing on Kepler-62f, the star in the sky would look bigger than our sun does, but "the illumination level would be like walking around on Earth on a cloudy day," Borucki said at a press briefing. "It drops by a factor of five."

Kepler-62e appears to be 60% larger than our planet and a little closer to its host star; this one could be a "water world" of mostly deep oceans, he said. It circles its star in 122.4 days.

"All these planets that we're finding are quite different than planets in our own solar system," Borucki said.

Kepler-69c appears to orbit a star similar to Earth's sun, Barclay said. As it's estimated to be about 70% larger than Earth, it may also be a water world, with oceans thousands of kilometers deep. This planet is also exciting because it is the smallest scientists have found that orbits a sun-like star in the habitable zone.

It's not likely to have a rocky surface, Barclay said. According to what little we know about it, Kepler-69c is probably significantly warmer than Earth and could be more like Venus.

"Probably, if there is life, it would be very unlike what we see on our own world," Barclay said.

If scientists' notions of a "habitable zone" were applied to our own solar system, both Earth and Mars would fit the bill. But Mars doesn't have enough gravity to hold onto an atmosphere that could heat it sufficiently, said Lisa Kaltenegger, research group leader at the Max Planck Institute for Astronomy in Heidelberg, Germany, in a press conference. Still, the Mars rover Curiosity has uncovered evidence that the Red Planet was, indeed, hospitable to life in the past.

Other worlds that may have life

Borucki said the new planets are "by far" better candidates for life than any others we know about, but a handful of others also have been identified as potentially capable of hosting life.

You may recall planet Kepler-22b, which was announced in December 2011 and also was hailed as a potential candidate for hosting life. That planet had a radius 2.4 times that of Earth and is 600 light-years away.

Kepler-22b was thought to have a temperature similar to that of Earth, according to modeling by Borucki and colleagues. The planet's host star is dimmer and cooler than our sun, but the planet is also 15% closer than we are to the sun.

There is also a planet called Gliese-581g, discovered in September 2010, which is thought to be even more like Earth than Kepler-22b in terms of its suitability for plants and animals. It's only 20 light-years from Earth -- a lot closer than the newly discovered planets, though there has been some controversy about its existence.

In its solar system there is another planet, Gliese-581d, that is also of interest in the search for life, according to the Planetary Habitability Laboratory at the University of Puerto Rico at Arecibo. The group's catalog lists a few other candidates.

However, just like the other planets, we haven't seen or tested the atmospheres of any of these planets, so whether they're habitable remains theoretical.

Often, when you find an example of a kind of planet, you start seeing a lot of them, said Sara Seager, professor of planetary science at Massachusetts Institute of Technology. She used to be part of the Kepler team but is now independent.

"Planets in the habitable zones of stars must be everywhere," she said.

Seager called the discovery of the three planets "a huge milestone," but her excitement is tempered because potentially habitable planets have been announced in the past and there's currently no way to get more details, given how far away they are.

"We'll possibly never know if these particular ones do have water oceans or signs of life," she said.

More space news on CNN's Light Years

Identifying planets, not atmospheres

The goal of the Kepler mission wasn't to find alien lifeforms, however. The satellite is supposed to investigate Earth-sized planets around stars that resemble our sun.

The Kepler telescope, launched in 2009, allows scientists to measure changes in brightness of individual stars over time; these dimming events signal that a planet is nearby. Scientists undertake sophisticated calculations to verify that such signals are planets and not passing rocks.

The satellite finds planets that are very far away because it's surveying so many stars. Imagine, said Seager, that you are in Times Square and you want to see 150,000 people at once. You wouldn't be able to do it in such a way that you could see any details of the people; you'd have to get far enough away that that many people would fit into your field of view.

In total, Kepler has found 122 confirmed planets and more than 2,700 planet candidates. A total of seven confirmed planets were announced Thursday -- the three in the habitable zone, and four others that are not.

This isn't the only planet-finding technique. The Gliese-581 system was found with the Keck I Telescope in Hawaii, using what is called the radial velocity method. The telescope's spectrometer allows scientists to look for wobbles in the motion of a star, which happens in response to the gravity of nearby planets.

It would take a different kind of mission to investigate the atmosphere of one of these distance planets to find out answers to the most-pressing questions. Is there carbon dioxide and water? Is there oxygen?

"Future NASA missions are going to focus on more nearby stars that we can look at in much more detail," Barclay said.

You can read more about the Kepler discoveries at the mission website.

More space and science news from CNN Light Years

ADVERTISEMENT
Part of complete coverage on
Space
July 23, 2014 -- Updated 1653 GMT (0053 HKT)
Seems NASA's fascination with the moon is in the past. It's focused on something far more menacing: incoming asteroids
July 15, 2014 -- Updated 0356 GMT (1156 HKT)
Scientists looking for signs of life in the universe -- as well as another planet like our own -- are a lot closer to their goal than people realize.
July 25, 2014 -- Updated 1237 GMT (2037 HKT)
Back in July 1969, I stood on the talcum-like lunar dust just a few feet from our home away from home, Eagle, the lunar module that transported Neil Armstrong and me to the bleak, crater-pocked moonscape.
July 16, 2014 -- Updated 1311 GMT (2111 HKT)
solar flare july 2014
From Earth, the sun appears as a constant circle of light, but when viewed in space a brilliant display of motion is revealed.
July 17, 2014 -- Updated 1731 GMT (0131 HKT)
The full moons of this summer -- July 12, August 10 and September 9 -- are supermoons, as NASA calls them.
June 29, 2014 -- Updated 1551 GMT (2351 HKT)
If you think you saw a flying saucer over Hawaii, you might not be crazy -- except what you saw didn't come from outer space, though that may be its ultimate destination.
June 27, 2014 -- Updated 0147 GMT (0947 HKT)
The U.S. space shuttle program retired in 2011, leaving American astronauts to hitchhike into orbit. But after three long years, NASA's successor is almost ready to make an entrance.
June 13, 2014 -- Updated 1421 GMT (2221 HKT)
When I first poked my head inside Virgin Galactic's newest spaceship, I felt a little like I was getting a front-row seat to space history.
June 10, 2014 -- Updated 2303 GMT (0703 HKT)
The sun is putting on a fireworks show again.
June 24, 2014 -- Updated 2302 GMT (0702 HKT)
A year is a very long time on Mars -- 687 days. NASA's Curiosity rover can attest that it's enough time for some unexpected life changes.
May 8, 2014 -- Updated 2205 GMT (0605 HKT)
It's hard to describe billions of years of cosmic history. But scientists have used a code to create a model of how the universe as we know it today might have evolved.
May 2, 2014 -- Updated 1800 GMT (0200 HKT)
At least one corner of the solar system may be serving up an ice-and-water sandwich, with the possibility of life on the rocks.
April 9, 2014 -- Updated 1503 GMT (2303 HKT)
Planetary nebula Abell 33 has taken on romantic proportions.
April 8, 2014 -- Updated 1555 GMT (2355 HKT)
You can't see it happening on Earth, but space itself is stretching. Ever since the Big Bang happened 13.8 billion years ago, the universe has been getting bigger.
March 26, 2014 -- Updated 2059 GMT (0459 HKT)
Scientists have added another celestial body to the short list of objects in our solar system that have rings around them.
March 27, 2014 -- Updated 1759 GMT (0159 HKT)
Astronomers have discovered a dwarf planet that's even farther away than Pluto.
February 28, 2014 -- Updated 1259 GMT (2059 HKT)
Our galactic neighborhood just got a lot bigger. NASA announced the discovery of 715 new planets.
March 18, 2014 -- Updated 1437 GMT (2237 HKT)
Scientists have made a breakthrough in understanding how our world as we know it came to be.
February 25, 2014 -- Updated 2027 GMT (0427 HKT)
From a sheep ranch in Western Australia comes the oldest slice of Earth we know.
February 19, 2014 -- Updated 1902 GMT (0302 HKT)
Cassiopeia A was a star more than eight times the mass of our sun before it exploded in the cataclysmic, fiery death astronomers call a supernova.
February 10, 2014 -- Updated 2207 GMT (0607 HKT)
Researchers have found clues that water could be flowing in the present, at least during warm seasons.
February 15, 2014 -- Updated 1602 GMT (0002 HKT)
The "jelly doughnut" rock that seemed to appear out of nowhere on Mars last month did not fall out of an extraterrestrial pastry box.
February 7, 2014 -- Updated 0356 GMT (1156 HKT)
It's a dot in the sky.
February 13, 2014 -- Updated 0744 GMT (1544 HKT)
Reports of Jade Rabbit's demise may have been premature.
January 16, 2014 -- Updated 1358 GMT (2158 HKT)
It's rare for astronomers to spot a planet in a star cluster. That's partly why a cluster called Messier 67 is so special: We now know that it has three planets orbiting stars.
ADVERTISEMENT