Kepler Discovers Earth's Older Sister

NASA’s Kepler space telescope has found the closest match yet to a world that is similarly sized to Earth and circling a sun-like star at the right distance for liquid surface water, a condition believed to be necessary for life, scientists said Thursday.

NASA's Kepler space telescope has found the closest match yet to a world that is similarly sized to Earth and circling a sun-like star at the right distance for liquid surface water, a condition believed to be necessary for life, scientists said Thursday.

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The newly found world, called Kepler-452b, is located about 1,400 light-years away in the constellation Cygnus.

"In my mind, this is the closet thing we have to another planet like the Earth," Jon Jenkins, head of Kepler data analysis at NASA's Ames Research Center in Moffett Field, Calif., told reporters on a conference call Thursday.

Kepler-452b is about 60 percent wider than Earth and estimated to have five times the mass, making it most likely a rocky world. It circles a G2-type star very much like the sun, but estimated to be closer to 6 billion years old, compared to the 4.6-billion-year age of the solar system.

"That's a considerable opportunity for life to arise, should all the necessary ingredients and conditions for life exist on this planet," Jenkins said.

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"It's simply awe-inspiring to consider that this planet has spent 6 billion years in the habitable zone of its star," Jenkins said. "That's considerable time and opportunity for life to arise somewhere on its surface, or in its oceans, should all the necessary ingredients and conditions for life exist on this planet."

Kepler-452b orbits its parent star every 385 days, so it is located just about 5 percent farther away from the star than Earth circles the sun. The star's age means it's about 10 percent bigger and 20 percent brighter than the sun, Jenkins said.

If Kepler-452b is rocky, scientists expect it would be about five times more massive than Earth and twice Earth's surface gravity. It would have a thicker, cloudier atmosphere and most likely active volcanoes, Jenkins added.

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Today, Kepler 452-b receives 10 percent more energy from its parent star than Earth does from the sun, but that wasn't always the case.

"When this star was young, it was only about 80 percent of its present size and 64 percent as bright, so the planet received 64 percent as much energy then," Jenkins said.

As the star continues to grow, Kepler 452-b will no longer be in a habitable, water-friendly zone, a future that awaits Earth as well.

Kepler-452b is the first of 12 potential Earth-twins that has been confirmed as a planet, all of which circle in life-friendly orbits around their parent stars. More than half of those stars are the same type as the sun.

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"A lot of them are very interesting candidates. For example, one of them appears to be just 15 percent larger than Earth ... and receiving about three-fourths the energy that Earth does. There's a lot of other ones similar to that that are really tantalizing to go after," Jeff Coughlin, a Kepler research scientist at SETI Institute in Mountain View, Calif., told Discovery News.

Overall the list of candidate planets found by Kepler has reached 4,696. Another 1,030 Kepler finds have been confirmed, NASA said.

The research will be published in an upcoming issue of The Astronomical Journal.

This artist's concept depicts one possible appearance of the planet Kepler-452b, the first near-Earth-size world to be found in the habitable zone of star that is similar to our sun.

Exquisite Exoplanetary Art

Sept. 19, 2011 --

They're alien worlds orbiting distant stars far out of reach of detailed imaging by even our most advanced telescopes. And yet, day after day, we see vivid imaginings of these extrasolar planets with the help of the most talented space artists. The definition of an extrasolar planet -- or "exoplanet" -- is simply a planetary body orbiting a star beyond our solar system, and nearly 700 of these extrasolar worlds have been discovered so far (plus hundreds more "candidate" worlds). With the help of NASA's Kepler space telescope, the ESO's High Accuracy Radial velocity Planet Searcher (HARPS), French COROT space telescope and various other advanced exoplanet-hunting observatories, we are getting very good at detecting these worlds, but to glean some of the detail, we depend on artist's interpretations of fuzzy astronomical images and spectral analyses. That's the way it will be until we build a vast telescope that can directly image an exoplanet's atmosphere or physically travel to an alien star system. So, with the flurry of recent exoplanet discoveries, Discovery News has collected a few of the dazzling pieces of art born from one of the most profound searches mankind has ever carried out: the search for alien worlds orbiting other stars; a journey that may ultimately turn up a true "Earth-like" world.

The Transit

As an exoplanet passes in front of its star as viewed from Earth, a very slight dip in starlight brightness is detected. Observatories such as NASA's Kepler space telescope use this "transit method" to great effect, constantly detecting new worlds.

Hot Jupiters

Some exoplanets orbit close to their parent stars. Due to their close proximity and generally large size, worlds known as "hot Jupiters" are easier to spot than their smaller, more distant-orbiting cousins.

Habitable Worlds

The primary thrust of exoplanet hunting is to find small, rocky worlds that orbit within their stars' "habitable zones." The habitable zone, also known as the "Goldilocks zone," is the region surrounding a star that is neither too hot nor too cold. At this sweet spot, liquid water may exist on the exoplanet's surface. Where there's water, there's the potential for life.

A Phantom

Usually, exoplanet hunters look for the slight dimming of a star or a star's "wobble" to detect the presence of an exoplanet. However, in the case of Kepler-19c, its presence has been detected by analyzing its gravitational pull on another exoplanet, Kepler-19b. Kepler-19c is therefore the Phantom Menace of the exoplanet world.

Keeping Warm

The habitable zone seems to be the pinnacle of extraterrestrial living. If you're an alien with similar needs to life on Earth, then you'll need liquid water. If your planet exists outside your star's habitable zone, well, you're in trouble. Either your world will be frozen like a block of ice, or boiling like a kettle. But say if your world had the ability to extend your star's habitable zone? There may be some atmospheric factors that might keep water in a comfy liquid state. Even better, if you like deserts, a dry world could even be oddly beneficial.

Crazy Aurorae

Planets with a global magnetic field, like Earth, have some dazzling interactions with the winds emanating from their stars. The high-energy particles bombard the planet's atmosphere after being channeled by the magnetism. A wonderful auroral lightshow ensues. But say if there's an exoplanet, with a magnetosphere, orbiting really close to its star? Well, stand back! The entire world would become engulfed in a dancing show, 100-1000 times brighter than anything we see on Earth.

The "Candidates"

"Candidate" exoplanets are often mentioned, especially when talking about detections by the Kepler space telescope. But what does this mean? As a world passes in front of its star, slightly dimming the starlight, this isn't considered a "confirmed" exoplanet detection. To make sure that signal is real, more orbital passes of the exoplanet need to be logged before a bona fide discovery can be announced. Until then, these preliminary detections are called exoplanet candidates.

Angry Suns, Naked Planets

Exoplanets come in all sizes and all states of chaos. Some might have wonky orbits, others might be getting naked. Other times, they're simply being ripped apart by X-rays blasted from their parent star. Bummer.


Super-Earths get a lot of press. Mainly because "Earth" is mentioned. Sadly, most of these worlds are likely completely different to anything we'd call "Earth." And you can forget calling the vast majority of them "Earth-like." It's simply a size thing -- they're bigger than Earth, yet a lot smaller than Jupiter, hence their name, "super-Earth." Easy.

Let's Go!

For now, we have to make do with artist's renditions of exoplanets for us to visualize how they may look in their alien star systems. However, plans are afoot to send an unmanned probe to an interstellar destination. Although these plans may be several decades off, seeing close-up photographs of these truly alien worlds will be well worth the wait.