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|作者：英语点津 文章来源：China Daily 点击数：41 更新时间：2017/4/26|
Point a high-powered telescope at the constellation Cetus, the sea monster, and it is just possible to make out a dim red dwarf star shining in the tail.
Although it might seem unspectacular, orbiting around that star is a rocky planet that could hold the answer to whether we are alone in the universe.
Scientists say the planet is a ‘Super-Earth’ which is the best place to look for signs of life outside of the Solar System.
Early indications suggest it has an atmosphere, and sits within the ‘Goldilocks Zone’ where it is neither too hot nor too cold for liquid water to exist.
And it is only 40 light years from Earth meaning that it could be possible to send a signal.
“This is the most exciting exoplanet I’ve seen in the past decade,” said lead author Jason Dittmann of the Harvard-Smithsonian Center for Astrophysics.
“We could hardly hope for a better target to perform one of the biggest quests in science -- searching for evidence of life beyond Earth.”
The planet was found by an international team of scientists who have been studying data from European Space Observatory’s High Accuracy Radial velocity Planet Searcher (HARPS) instrument which looks for regular changes in brightness of stars, which suggests a planet is passing by in orbit.
The new world - dubbed LHS 1140b - is ten times closer to its parent star than Earth but because a red dwarf is far cooler than our own yellow dwarf, the planet still sits in the habitable zone.
“The present conditions of the red dwarf are particularly favourable -- LHS 1140b spins more slowly and emits less high-energy radiation than other similar low-mass stars,” added team member Nicola Astudillo-Defru from Geneva Observatory, Switzerland.
For life as we know it to exist, a planet must have liquid surface water and retain an atmosphere.
In this case, the planet’s large size and closeness to its sun means that a magma ocean could have existed on its surface for millions of years, which fed steam into the atmosphere, replenishing the planet with water.
Astronomers estimate the age of the planet to be at least five billion years, just a little older than Earth. They also deduced that it has a diameter 1.4 times larger than the Earth.
But with a mass around seven times greater than the Earth, and hence a much higher density, it implies that the exoplanet is probably made of rock with a dense iron core.
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