Astronomers have discovered eight new planets in the so-called “Goldilocks” habitable zone, orbiting at a distance where liquid water, and possibly life, can exist. Two planets are said to be the most similar to Earth of any known exoplanets to date.
This artist’s conception depicts an Earth-like planet orbiting an evolved star that has formed a stunning “planetary nebula.” Earlier in its life, this planet may have been like one of the eight newly discovered worlds orbiting in the habitable zones of their stars. David A. Aguilar (CfA)
“Most of these planets have a good chance of being rocky, like Earth,”Guillermo Torres, the lead scientist from the Harvard-Smithsonian Center for Astrophysics (CfA) in Cambridge, US, told a meeting of the American Astronomical Society in Seattle.
According to the astronomers, the two most Earth-like planets of the group are called Kepler-438b and Kepler-442b. Both orbit red dwarf stars that are smaller and cooler than the Sun. Their daily routine is as follows: Kepler-438b circles its star every 35 days, while Kepler-442b completes one orbit every 112 days.
According to the scientists’ calculations, with a diameter just 12 percent bigger than Earth, Kepler-438b boasts a 70-percent chance of being rocky. Its closest rival, Kepler-442b, is about one-third larger than Earth, but still has a 60-percent chance of being rocky.
To be in the habitable zone, an exoplanet must receive about as much sunlight as Earth. Too much and any water would boil away as steam, while too little means it will freeze solid, scientists explain. “For our calculations we chose to adopt the broadest possible limits that can plausibly lead to suitable conditions for life,” Torres said.
Kepler-438b gets about 40 percent more light than Earth. To compare, Venus, the second planet from the sun, gets twice as much solar radiation as Earth. So, the team believes, Kepler-438b enjoys a 70 percent probability of being in the habitable zone of its star.
Kepler-442b gets about two-thirds as much light as Earth. The scientists give the champion a 97 percent chance of being in the habitable zone.
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