NASA's Kepler mission has announced the discovery of a larger, older "cousin" of Earth, potentially bringing us a step closer to the realization we are not alone in the universe.
The near-Earth-size planet, dubbed Kepler-452b, is orbiting within the habitable zone (the distance at which liquid water is possible) of a G2-type star, like our sun.
"On the 20th anniversary year of the discovery that proved other suns host planets, the Kepler exoplanet explorer has discovered a planet and star which most closely resemble the Earth and our sun," said John Grunsfeld, associate administrator of NASA's Science Mission Directorate at the agency's headquarters in Washington. "This exciting result brings us one step closer to finding an Earth 2.0."
The Kepler-452 system is located 1,400 light-years away in the constellation Cygnus. It exists in a solar system with five other known planets. Kepler-452b is believed to have a diameter 60 percent larger than Earth, and while its mass has not been concretely determined, it is estimated to be about five times more massive than Earth, according to a NASA press conference. The researchers also believe the planet has a good chance of being rocky, meaning it would be very similar to our home planet and is characterized by active volcanoes and more cloud cover than is seen on Earh.
The fascinating planet has a 385-day orbit, which is only about 5 percent longer than our own orbit, and is only about 5 percent farther away from its host star. The parent star is estimated to be about six billion years old, which is 1.5 billion years older than our sun. It is also believed to be about the same temperature as the Sun, and about 10 percent larger and 20 percent brighter.
"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," said Jon Jenkins, Kepler data analysis lead at NASA's Ames Research Center in Moffett Field, California, who led the discovery team. "It's awe-inspiring to consider that this planet has spent [six] 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."
This planet has been deemed the "most Earth-like" ever discovered because the sunshine and predicted rockiness would feel a lot like home. On the other hand, the planet is believed to have twice the gravity of Earth. This means astronauts visiting the planet in the distant future would get quite a workout trying to move against the strong tug of the planet's gravity. While this would be a challenge, the researchers do not believe it would be impossible.
Today, Kepler-452b is recieving about 10 percent more energy from its host star than Earth does from the Sun. If the planet had the same mass as the Eath it would already be experiencing the runaway greenhouse effect and water loss, but since it is about five times more massive this is not expected to occur for about 500 million more years.
In addition to this groundbreaking discovery, the Kepler mission has added a whopping 521 new exoplanet candidates from May 2009 to May 2013, raising the overall number to 4,696. Twelve of these new candidates have diameters between one to two times that of Earth, and are believed to orbit within their star's habitable zone. Nine of these planets are orbiting stars that are similar in size and temperature to our Sun.
"We've been able to fully automate our process of identifying planet candidates, which means we can finally assess every transit signal in the entire Kepler dataset quickly and uniformly," said Jeff Coughlin, Kepler scientist at the SETI Institute in Mountain View, California, who led the analysis of a new candidate catalog. "This gives astronomers a statistically sound population of planet candidates to accurately determine the number of small, possibly rocky planets like Earth in our Milky Way galaxy."
These findings are presented in the seventh Kepler Candidate Catalog, and were published in a recent edition of the Astronomical Journal.
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