If humankind ever is to escape this not-so-gently-used rock called Earth, we’ll have to find somewhere hospitable to stay.
That’s what makes NASA’s Thursday announcement of the discovery of a planet much like ours so, ahem, earth shattering. Kepler-452b is the first confirmation of a near-Earth-size planet that can sustain liquid water and orbits a star much like the Sun. It was found through data collected by the Kepler Space Telescope, launched into space more than six years ago.
“As far as we can tell,” said John Grunsfeld, associate administrator for NASA’s Science Mission Directorate, “it’s a pretty good, close cousin to our planet and sun.”
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A bigger, heavier, older and quite distant cousin, the researchers added. Kepler-452b is 60 percent larger in diameter than our planet and packing twice the gravitational punch, while its sun is 6 billion years old (ours is 4.5 billion years) and located 1,400 light-years away in the constellation Cygnus.
Still, Kepler-452b carries enough similarities to Earth to seize scientists’ attention:
- Its orbit around star Kepler-452 is located in the “habitable zone,” not so close to its star where water vaporizes or so distant where water freezes.
- Also, that heliocentric orbit takes 385 days, just 5 percent longer than our solar year.
- The planet has “a better-than-even” chance of being rocky with, likely, very active volcanoes.
- Kepler-452 is about the same temperature as the Sun, although it is 20 percent brighter with a diameter 10 percent larger.
As for the possibility of life on Kepler-452b, that remains a mystery. But as Jon Jenkins, Kepler data analysis lead at NASA’s Ames Research Center, noted, for a planet to spend 6 billion years in its solar system’s habitable zone is more than enough time for life forms to develop either on the planet’s surface or in its oceans, “should all the necessary ingredients and conditions exist.”
Didier Queloz, professor of astrophysics at Cambridge University, noted it is only 20 years since the announcement of the first “exoplanet” discovery. And now, Kepler-452b brings the total number of confirmed planets to 1,030.
In addition, NASA said it has found 11 new, small, habitable zone “candidate” planets, with diameters one to two times that of Earth, although further research is needed to verify these are actual planets. Of those dozen, nine orbit stars similar to the Sun in size and temperature.
Confirmation of Earth-like conditions of Kepler-452b and the others comes from 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. Measurements taken at these sites helped the research team confirm Kepler-452b’s planetary status, refine the known size and brightness of its host star, as well as chart the size of the planet and its orbit.
If a dozen possible Earth-like planets don’t seem like many considering the vastness of the galaxy, think again. Jenkins pointed out for every Kepler-452b found, there are about 50 that can’t be seen due to the limits of detection and alignment issues with the telescope.
“We can say that near-Earth-like planets in the habitable zone of Sun-like stars are common in our galaxy,” Jenkins said.
In all, the number of planet candidates detected by the Kepler mission is up to 4,696.
Kepler’s discoveries are a testament to two necessary qualities of space explorers: infinite patience and powerful telescopes.
Shortly after the observatory was launched into orbit around the Sun in March 2009, the telescope was pointed toward an arm of our Milky Way. Kepler then snapped picture after picture in search of telltale signs of orbiting planets. Grunsfeld said these clues took the forms of eclipse-like sights: dimming starshine as planets transited past their stars and blocked Kepler’s vision. Data was transmitted to Earth once a month.
This unblinking gaze continued for four years before the failure of the spacecraft’s guidance system, which steadied the observatory for clearer photos. After the second of four reaction wheels went offline in May 2013, it seemed Kepler’s mission was over—until researchers developed a second use for the $600 million satellite.
In June 2014, Kepler began its “K2” mission, in which the craft’s position was adjusted every 80 days so it could continue viewing the sections of the cosmos while keeping sunlight away from its camera. As a result, Kepler’s planet-searching mission continues, but in a completely new way.
“It was crushing when that second reaction wheel failed,” Grunsfeld said. “But, in fact, it’s the best worst thing that could’ve happened to Kepler.”
