Space

Kepler discovers "Earth's bigger, older cousin"

Artist's concept of Kepler-425b
Artist's concept of Kepler-425b
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Artist's concept of Kepler-425b
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Artist's concept of Kepler-425b
NASA's exoplanet missions
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NASA's exoplanet missions
Progress in seeking Earthlike exoplanets
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Progress in seeking Earthlike exoplanets
Comparing the habitable zones of the Sun and Kepler-425
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Comparing the habitable zones of the Sun and Kepler-425
Graph showing habitable zones of various exoplanets
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Graph showing habitable zones of various exoplanets
Age of Earth and Kepler-425b, showing their progress through the habitable zone
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Age of Earth and Kepler-425b, showing their progress through the habitable zone
Kepler's small habitable zone planets
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Kepler's small habitable zone planets
Kepler planet candidates and those just added
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Kepler planet candidates and those just added
New Kepler small habitable zone candidate planets
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New Kepler small habitable zone candidate planets
Kepler candidate planet assessment graph
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Kepler candidate planet assessment graph
Kepler-425b and the first detected exoplanet
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Kepler-425b and the first detected exoplanet
The Kepler space telescope
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The Kepler space telescope
The main Earth-like exoplanets
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The main Earth-like exoplanets

The odds of finding a habitable planet outside of our Solar System got a significant boost today, as NASA announced the discovery of the most Earthlike world orbiting the most Sunlike star yet. Named Kepler-425b, the new world located 1,400 light-years away in the constellation Cygnus was detected by the Kepler space telescope. It has been characterized by the space agency as "Earth's bigger, older cousin."

According to NASA, planet Kepler-425b is remarkable because it combines a number of factors that make it the most likely candidate for habitability found outside the Solar System so far. It's not only roughly Earth-sized, but it also orbits in the habitable zone of a sun-like star.

To date, the Kepler mission has confirmed the existence of 1,030 exoplanets, but so far the search for a planet similar enough to Earth to support life has been an exercise in extremely rough approximations. The technique used by the unmanned Kepler space telescope (launched in 2009) to detect exoplanets relies on measuring the dip in a star's light as a planet passes in front of it. This tends to favor finding large planets orbiting very close to their stars, which means that the easiest ones to find have been very hot super-Jupiters.

Comparing the habitable zones of the Sun and Kepler-425
Comparing the habitable zones of the Sun and Kepler-425

Another problem is that even if a small rocky planet like Earth is found, it has to be in its star's habitable zone. That is, its distance from its star is such that the possible surface temperature could allow liquid to exist, so it can't be too close or too far away.

However, one particular sticking point until today is the kind of star these planets revolve around. The most common type of stars in our galaxy are red dwarfs, which are K or M types. Since they're so numerous, it's no surprise that most exoplanets are found orbiting them, but these are small, old, and cold stars, which poses many problems for the habitability of their planets.

Earth, on the other hand, orbits a young, medium-sized G2 star, which is relatively warm and stable with a lifespan long enough for life to establish itself. Since so little is known about other star systems, and ours is the only one known to have life, scientists tend to favor sun-like stars as the best candidates for habitable planets.

The Kepler space telescope
The Kepler space telescope

These are the reasons why Kepler-425b has NASA so excited. According to NASA scientists at today's press conference, they believe from computer models that it's a rocky planet 60 percent larger than Earth with five times the mass and a surface gravity twice that of ours. It may have active volcanoes, and an atmosphere that may be thicker than Earth's. Equally important, its 385-day orbit is similar to that of Earth and is only five percent farther from its star – putting it smack in the habitable zone.

But the clincher is that the planet's star, Kepler-425, is also a G2-type. It's 6 billion years old, which makes it older than the Sun by 1.5 billion years, is 10 percent bigger and 20 percent brighter, but has the same temperature, though it emits more energy. Put this all together and Kepler-425b is the best chance yet for an exoplanet where life could exist. However, NASA does point out that the composition of the atmosphere and other factors have yet to be determined, so don't pack your bags yet.

Age of Earth and Kepler-425b, showing their progress through the habitable zone
Age of Earth and Kepler-425b, showing their progress through the habitable zone

NASA says that the Kepler data was confirmed by ground observations from the University of Texas at Austin's McDonald Observatory, the Fred Lawrence Whipple Observatory on Mt. Hopkins, Arizona, and the W. M. Keck Observatory atop Mauna Kea in Hawaii.

"We can think of Kepler-452b as an older, bigger cousin to Earth, providing an opportunity to understand and reflect upon Earth’s evolving environment," says Jon Jenkins, Kepler data analysis lead at NASA's Ames Research Center in Moffett Field, California. "It’s awe-inspiring to consider that this planet has spent 6 billion years in the habitable zone of its star; longer than Earth. That’s substantial opportunity for life to arise, should all the necessary ingredients and conditions for life exist on this planet."

NASA also announced today that the latest Kepler findings have produced 521 new planetary candidates. This brings the total to 4,696, with 12 Earthlike candidates orbiting in their stars' habitable zones.

The recent discoveries have been accepted for publication in The Astronomical Journal.

The video below outlines the movement of Kepler-425b and the Earth through their respective habitable zones over time.

Source: NASA

Kepler -- Window Into Time

9 comments
danmar
"1,400 light-years away" Not very useful is it? :-) Hey! Maybe Bugatti can build the world's fastest spaceship next! What an experience it would be to visit the planet though wouldn't it? Even if you died the next day!
salcen
it would be interesting if they found out this planet has moons.
MarylandUSA
Every time I read a phrase like "60 percent larger than Earth," I wonder, "Did the writer mean that Kepler-452b is 60 percent wider or 60 percent greater in volume?" Judging from its mass (5 times that of Earth), I'd say he meant that it's 60 percent wider; that ratio would give it just over four times the volume of Earth ( http://www.calculateme.com/cVolume/VolumeOfSphere.htm ), which correlates well with five times the mass, especially if Kepler-452b is composed of more rock and less water.
Douglas Bennett Rogers
The time on the space ship will approach zero as the speed approaches the speed of light. In Newtonian mechanics it takes about one year to reach the speed of light at 1g. For antimatter fuel this is a mass ratio on the order of one. For fusion fuel, around 200. At some point, the fusion ramjet effect would kick in. This is only about 4 Mev so it is very ineffiecient at relativistic speed.
Scott in California
I share more characteristics with any person randomly chosen walking down the street, than 425-B and Earth share. Is every person my "cousin"?? Let's leave the erroneous use of "cousin" out (where is the common source that cousins possess?) and simply state "fellow planet".
michael_dowling
Unless there is a civilization there that is thousands of years old,I agree with danmar. Even if there is a very old culture on the planet,they have probably stopped using radio for communication millennia ago.
Mark Randombard
Just curious; if it has five times the mass, how is the surface gravity only twice that of earth?
PetriPulkkinen
We just need access to the "Secret Space Program" and then we can go and check the rock out. They've probably already been there. Google Corey Goode he's the latest whistleblower about the SSP.
maarvarq
PetriPulkkinen, the 60% greater planetary radius accounts for 5x mass but 2x surface gravity (inverse square law). 2x surface gravity is a bit of a disincentive to move there, even if you could breathe the air, and get there within a lifetime. Think of how much faster and stronger the wildlife would be!