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Monday, 19 June 2017

NASA’s Kepler Telescope has detected Ten Earth size planets that may have life

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NASA has announced that its Kepler space telescope has updated its catalogue of extrasolar planets, or exoplanets, with 219 new candidates. Ten of these newly spotted exoplanets are nearly the size of Earth and orbit in their star's habitable zone, meaning temperatures could be right for liquid water to exist on the surface.

The new announcement adds to a long list of planet candidates discovered by Kepler since the telescope achieved first light in April 2009. The Kepler catalogue now includes 4,034 planet candidates, 2,335 of which have been verified as exoplanets by follow-up observations from other telescopes. Of these thousands of discovered planets, about 50 are roughly Earth-sized and orbit in a habitable zone, and more than 30 of those have been verified as bona fide planets by additional observations.

"The Kepler data set is unique, as it is the only one containing a population of these near Earth-analogs–planets with roughly the same size and orbit as Earth," said Mario Perez, Kepler program scientist at NASA, in a press release. "Understanding their frequency in the galaxy will help inform the design of future NASA missions to directly image another Earth."

Kepler detects exoplanets by measuring a temporary reduction in light emissions coming from a star when the planet moves in front, or transits. These measurements can also be used to determine the approximate radius of the discovered exoplanets, work that is generally done by additional telescopes such as the W. M. Keck Observatory in Hawaii.

The researchers found that smaller exoplanets fall into two distinct categories: Earth-sized planets and gas planets smaller than Neptune, commonly called mini-Neptunes. Very few planets smaller than Neptune fall outside of these two categories. Planetary scientists hope to use this growing repository of data to learn about planet formation throughout the galaxy and to answer a more enticing question: How many planets like Earth are out there?

"We like to think of this study as classifying planets in the same way that biologists identify new species of animals," said Benjamin Fulton, doctoral candidate at the University of Hawaii and lead author of a study about the updated Kepler catalogue. "Finding two distinct groups of exoplanets is like discovering mammals and lizards make up distinct branches of a family tree."

The next step in exoplanet study is to determine what elements are present in these alien atmospheres. It will be difficult, but a new generation of telescopes should be powerful enough to perform spectral analyses of the light from stars as it is filtered through the atmospheres of distant planets, revealing the chemical composition. Bio signatures such as abundant oxygen or complex organic molecules could be indicators of life on alien worlds.

In the meantime, Kepler forges ahead, cataloguing every exoplanet it can spot. It may be that one of those 4,000 entries in the Kepler catalogue is home to extra-terrestrial life.

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THE NASA STATEMENT IN FULL

NASA’s Kepler space telescope team has released a mission catalogue of planet candidates that introduces 219 new planet candidates, 10 of which are near-Earth size and orbiting in their star's habitable zone, which is the range of distance from a star where liquid water could pool on the surface of a rocky planet.

This is the most comprehensive and detailed catalogue release of candidate exoplanets, which are planets outside our solar system, from Kepler’s first four years of data. It’s also the final catalogue from the spacecraft’s view of the patch of sky in the Cygnus constellation.

With the release of this catalogue, derived from data publicly available on the NASA Exoplanet Archive, there are now 4,034 planet candidates identified by Kepler. Of which, 2,335 have been verified as exoplanets. Of roughly 50 near-Earth size habitable zone candidates detected by Kepler, more than 30 have been verified.

Additionally, results using Kepler data suggest two distinct size groupings of small planets. Both results have significant implications for the search for life. The final Kepler catalogue will serve as the foundation for more study to determine the prevalence and demographics of planets in the galaxy, while the discovery of the two distinct planetary populations shows that about half the planets we know of in the galaxy either have no surface, or lie beneath a deep, crushing atmosphere – an environment unlikely to host life.

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The findings were presented at a news conference Monday at NASA's Ames Research Center in California's Silicon Valley.

“The Kepler data set is unique, as it is the only one containing a population of these near Earth-analogs – planets with roughly the same size and orbit as Earth,” said Mario Perez, Kepler program scientist in the Astrophysics Division of NASA’s Science Mission Directorate. “Understanding their frequency in the galaxy will help inform the design of future NASA missions to directly image another Earth.”

The Kepler space telescope hunts for planets by detecting the minuscule drop in a star’s brightness that occurs when a planet crosses in front of it, called a transit.

Click here to visit NASA’S EXOPLANET ARCHIVE

This is the eighth release of the Kepler candidate catalogue, gathered by reprocessing the entire set of data from Kepler’s observations during the first four years of its primary mission. This data will enable scientists to determine what planetary populations – from rocky bodies the size of Earth, to gas giants the size of Jupiter – make up the galaxy’s planetary demographics.

To ensure a lot of planets weren't missed, the team introduced their own simulated planet transit signals into the data set and determined how many were correctly identified as planets. Then, they added data that appear to come from a planet, but were actually false signals, and checked how often the analysis mistook these for planet candidates. This work told them which types of planets were over counted and which were undercounted by the Kepler team’s data processing methods.

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“This carefully-measured catalogue is the foundation for directly answering one of astronomy’s most compelling questions – how many planets like our Earth are in the galaxy?” said Susan Thompson, Kepler research scientist for the SETI Institute in Mountain View, California, and lead author of the catalogue study.

One research group took advantage of the Kepler data to make precise measurements of thousands of planets, revealing two distinct groups of small planets. The team found a clean division in the sizes of rocky, Earth-size planets and gaseous planets smaller than Neptune. Few planets were found between those groupings.

Using the W. M. Keck Observatory in Hawaii, the group measured the sizes of 1,300 stars in the Kepler field of view to determine the radii of 2,000 Kepler planets with exquisite precision.

“We like to think of this study as classifying planets in the same way that biologists identify new species of animals,” said Benjamin Fulton, doctoral candidate at the University of Hawaii in Manoa, and lead author of the second study. “Finding two distinct groups of exoplanets is like discovering mammals and lizards make up distinct branches of a family tree.”

It seems that nature commonly makes rocky planets up to about 75 percent bigger than Earth. For reasons scientists don't yet understand, about half of those planets take on a small amount of hydrogen and helium that dramatically swells their size, allowing them to "jump the gap" and join the population closer to Neptune’s size.

The Kepler spacecraft continues to make observations in new patches of sky in its extended mission, searching for planets and studying a variety of interesting astronomical objects, from distant star clusters to objects such as the TRAPPIST-1 system of seven Earth-size planets, closer to home.

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