NASA Announces Kepler Mission Breakthrough: Two Earth-Sized Planets Orbiting Star
In its search for extraterrestrial life, NASA’s Kepler space telescope has found two new planets orbiting a distant sun-like star, and the researchers who made the find say these two are the first ever the size of Earth or smaller –a critical factor in the search for life elsewhere in the universe. Until now, scientists said their instruments were not sensitive enough to detect them
“Theoretical considerations imply that these planets are rocky, with a composition of iron and silicate,” wrote Francois Fressin of the Harvard-Smithsonian Center for Astrophysics, the leader of the team that made the discovery. “The outer planet could have developed a thick water vapour atmosphere.”
The two newly-found planets, called Kepler-20e and Kepler-20f orbiting a star about 950 light-years away, are too distant to be seen directly. Scientists measured the faint dimming of their host star as they passed in front of it toi estimate their size.
Kepler-20e and f are probably too hot to be friendly to life — one of them circles its sun in just six Earth days, and the other does it in 19. This newest Kepler find increases the odds that some day soon we will find a planet of just the right size and temperature to have at least a chance of being a habitable.
In less than 20 years, astronomers have gone from not knowing if other planets exist in the universe, to our current Kepler cataclog on almost 2000 planets. Our Milky Way galaxy may be home to at least two billion Earthlike planets, a recent study based on initial data from from Kepler space telescope shows — a number that is actually far lower than many scientists anticipated.
Based on what Kepler’s found so far, the study authors think that up to 2.7 percent of all sunlike stars in the Milky Way host so-called Earth analogs. As of this February, Kepler has confirmed 15 new planets and found an additional 1,235 planet candidates, including the smallest planet yet spied outside our solar system. Kepler will collect transit data for a minimum of three and a half years, allowing for a more complete planetary census at a later date.
“There are about a hundred billion sunlike stars within the Milky Way,” said study co-author Joe Catanzarite, a scientist with NASA’s Jet Propulsion Laboratory (JPL). “Two percent of those might have Earth analogs, so you have two billion Earth analog planets in the galaxy,” he added. “Then you start thinking about other galaxies. There are something like 50 billion, and if each one has two billion Earthlike planets, it’s mind boggling.”
Although the figure seems large, Catanzarite and co-author Michael Shao, also of JPL, say their results actually show that Earths are “relatively scarce,” which means a substantial effort will be needed to identify suitable target stars for followup missions designed to study the chemical signatures of Earth-size worlds. The chemical signals may hint whether the planets have oxygen atmospheres, liquid water — or even signs of life.
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