NASA’s space observatory Kepler may have discovered a possibly Earth-like planet, named Kepler-452b, a rocky world orbiting a Sun-like star at almost the exact same distance Earth orbits our own Sun.

“The new Earth” is located 1,400 light-years from us. It orbits a Sun-like star that is 4% more massive and 10% brighter than our Sun. Kepler-452b is 1.6 times the size of Earth and the scientists are fairly sure that it is a rocky world.

This artist’s concept depicts one possible appearance of the planet Kepler-452b, the first near-Earth-sized world to be found in the habitable zone of a star that is similar to our sun. Credits: NASA/JPL-Caltech/T. Pyle

A Kepler-452b year is 384.84 Earth days and the planet is 5% more distant from its star than our planet is from the Sun. This means the new planet is definitely in the habitable zone. In astronomy and astrobiology, the circumstellar habitable zone – CHZ, or simply the habitable zone, colloquially known as the Goldilocks zone, is the region around a star within which planetary-mass objects with sufficient atmospheric pressure can support liquid water at their surfaces.

The bounds of the CHZ are calculated using the known requirements of Earth’s biosphere, its position in the Solar System, and the amount of radiant energy it receives from the Sun. Due to the importance of liquid water to life, as it exists on Earth, the nature of the CHZ and the objects within is believed to be instrumental in determining the scope and distribution of Earth-like extraterrestrial life and intelligence.

The mass of Kepler-452b can’t be directly determined yet, but the scientists think it may be about five times that of Earth.

Kepler-452b/Earth comparison
Kepler-452b and its star compared to the Earth and the Sun and previously discovered Earth-like exoplanets. NASA/JPL-CalTech/R. Hurt.

This is not the first Earth-sized planet found in a habitable zone: for example, Kepler-186f, which was discovered last year about 490 light-years (151 pc) from the Earth, is more similar in size to our planet. But it is orbited a red dwarf star, smaller and cooler than the Sun.

We can’t know if there’s life on the planet, and probably we won’t know for a long time. But we’re on the track. John Grunsfeld, associate administrator of NASA’s Science Mission Directorate said that: “Kepler 452b is one small step in answering the question [of are we alone] today,”, in a press conference.

Launched in March 2009, Kepler is the first NASA mission to detect Earth-size planets orbiting distant stars in or near the habitable zone — the range of distances from a star in which the surface temperature of an orbiting planet might sustain liquid water. The telescope has since confirmed more than 1,000 exoplanets and more than 3,000 planet candidates spanning a wide range of sizes and orbital distances, including those in the habitable zone.

Kepler is part of NASA’s Discovery Program of relatively low-cost, focused primary science missions.

NASA Press Release about Kepler-452b

NASA’s Kepler Mission Discovers Bigger, Older Cousin to Earth

NASA’s Kepler mission has confirmed the first near-Earth-size planet in the “habitable zone” around a sun-like star. This discovery and the introduction of 11 other new small habitable zone candidate planets mark another milestone in the journey to finding another “Earth.”

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 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.”

Kepler-452b is 60 percent larger in diameter than Earth and is considered a super-Earth-size 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, Kepler data analysis lead at NASA’s Ames Research Center in Moffett Field, California, who led the team that discovered Kepler-452b. “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. The research paper reporting this finding has been accepted for publication in The Astronomical Journal.

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 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 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, presented in the seventh Kepler Candidate Catalog, will be submitted for publication in the Astrophysical Journal. These findings are derived from data publicly available on the NASA Exoplanet Archive.

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-size planets.

Ames manages the Kepler and K2 missions for NASA’s Science Mission Directorate. NASA’s Jet Propulsion Laboratory in Pasadena, California, managed Kepler mission development. Ball Aerospace & Technologies Corporation operates the flight system with support from the Laboratory for Atmospheric and Space Physics at the University of Colorado in Boulder.

Update: NASA retires Kepler Space Telescope

After nine and a half years of operation, the Kepler Space Telescope’s reaction control system fuel was depleted, and NASA announced its retirement on October 30, 2018.

During its service, the space telescope has observed 530,506 stars and detected 2,662 exoplanets.

The Legacy of NASA’s Kepler Space Telescope: More Planets Than Stars. After nine years spent in deep space collecting data that revealed our night sky to be filled with trillions of hidden planets, more planets even than stars, NASA is ending the Kepler Space Telescope’s science operations. Kepler leaves a legacy of more than 2,600 planet discoveries, some of which could be promising places for life, like Kepler-452b. Video credit: NASA/Ames Research Center


M. Özgür Nevres

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