The newly discovered Kepler-452b is the smallest planet to date discovered orbiting in the habitable zone — the area around a star where liquid water could pool on the surface of an orbiting planet — of a G2-type star like our Sun. The confirmation of Kepler-452b brings the total number of confirmed planets to 1,030.
“On the 20th anniversary year of the discovery that proved other suns host planets, the Kepler exoplanet explorer has discovered a planet and star that most closely resemble the Earth and our Sun,” said John Grunsfeld from NASA’s Science Mission Directorate at the agency’s headquarters in Washington, D.C. “This exciting result brings us one step closer to finding an Earth 2.0.”
Kepler-452b is 60 percent larger in diameter than Earth and is considered a super-Earth-sized planet. While its mass and composition are not yet determined, previous research suggests that planets the size of Kepler-452b have a good chance of being rocky.
While Kepler-452b is larger than Earth, its 385-day orbit is only 5 percent longer. The planet is 5 percent farther from its parent star, Kepler-452, than Earth is from the Sun. Kepler-452 is 6 billion years old, 1.5 billion years older than our Sun, has the same temperature, and is 20 percent brighter and has a diameter 10 percent larger.
“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 from 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.”
To help confirm the finding and better determine the properties of the Kepler-452 system, the team conducted ground-based observations at 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. These measurements were key for the researchers to confirm the planetary nature of Kepler-452b, to refine the size and brightness of its host star, and to better pin down the size of the planet and its orbit.
The Kepler-452 system is located 1,400 light-years away in the constellation Cygnus.
In addition to confirming Kepler-452b, the Kepler team has increased the number of new exoplanet candidates by 521 from their analysis of observations conducted from May 2009 to May 2013, raising the number of planet candidates detected by the Kepler mission to 4,696. Candidates require follow-up observations and analysis to verify they are actual planets.
Twelve of the new planet candidates have diameters between one to two times that of Earth and orbit in their star’s habitable zone. Of these, nine orbit stars that are similar to our Sun in size and temperature.
“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 data set quickly and uniformly,” said Jeff Coughlin from the SETI Institute in Mountain View, California. “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.”
Scientists now are producing the last catalog based on the original Kepler mission’s four-year data set. The final analysis will be conducted using sophisticated software that is increasingly sensitive to the tiny telltale signatures of Earth-sized planets.