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2017-06-22. Ten Earth-Sized Planets Found by Exoplanet-Hunting Telescope.

posted Jun 26, 2017, 9:30 PM by Alan Gould

By JoAnna Wendel, Earth & Space Science News, EoS, AGU. For GSS A Changing Cosmos chapter 8. Excerpt: NASA introduced 219 exoplanet candidates to the world on Monday. Ten of these are roughly Earth sized and orbit their stars in the so-called habitable zone, a distance at which temperatures could be ripe for liquid water. The candidate exoplanets appear in the eighth and newest catalog from the agency’s exoplanet-hunting Kepler space telescope and the final catalog from Kepler’s observations of the Cygnus constellation. The new catalog includes 4034 exoplanet candidates overall. Past “Kepler catalogs have shown us that small exoplanets are common,” Susan Thompson, lead author on the catalog study and a research scientist at the SETI Institute in Mountain View, Calif., told Eos. “With this [latest] catalog, we can show whether this is also true for exoplanets that are in orbital periods similar to those of the Earth.” Accompanying research also reveals that the majority of known exoplanets fall into two distinct sizes: rocky exoplanets up to 1.75 times the radius of Earth and Neptune-sized gassy exoplanets. The finding, soon to be published in The Astronomical Journal, deepens scientists’ understanding of exoplanet diversity. ...The team found that smaller exoplanets fall into two distinct size categories: rocky planets up to 1.75 times the radius of Earth and gassy planets 2–3.5 times the radius of Earth (or a touch shy of Neptune’s size). ...The researchers speculate that these two categories could stem from the bodies’ hydrogen and helium compositions when they first formed. Just enough gas, and the planet could balloon in size and “jump the gap” to become a mini-Neptune, said Andrew Howard, an astronomer at Caltech and principal investigator on the new research. But a small amount of gas would get blown away by radiation from the planet’s host star....  https://eos.org/articles/ten-earth-sized-planets-found-by-exoplanet-hunting-telescope