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New type of planet


Geneva-led team discovers ‘mega-Earth’




An international research team led by the University of Geneva has found an earth-like planet with 17 times more mass than our own, yet still made of rock – a phenomenon previously thought impossible.

Xavier Dumusque of the Harvard-Smithsonian Center for Astrophysics, who was involved in the research, said in a statement on Monday, “we were all very surprised when it became clear what we had found”, adding that it amounted to a new type of planet.

Previously, astronomers thought that planets with a similar mass – such as “gas giants” Uranus and Neptune – were always made up of a dense atmosphere composed of hydrogen and helium.

A so-called “super Earth”, at up to 14 times Earth’s mass, had already been discovered. This latest discovery, at 17 times Earth’s mass, has been dubbed a “mega-Earth”.

The first “mega-Earth” found by researchers is orbiting a small, hot star – similar to our own sun – in the Draco galaxy, 560 light-years away. It was discovered with the now-defunct Kepler space telescope.

With the telescope, researchers observed how the planet orbited its star and weakened its light. They were then able to calculate the size of the planet from the amount of light that was blocked out. With a diameter 2.3 times that of Earth, scientists assumed the planet was a sort of mini-Neptune.

However, using a precision spectrograph on the Italian Galileo Telescope, the researchers found the planet had a mass 17 times that of Earth.

Given that information, the planet’s density as calculated by the Kepler telescope was too large to be a gas planet, and it was determined to be the first-ever “mega-Earth” made of a rocky interior.

Although the planet is Earth-like in its makeup, it is not believed to harbour life. Researchers did not find any sign of life on the planet during their work.

The findings have been published in the journal Nature.

swissinfo.ch and agencies