![]() It relies on the ability of the gravitational field of a massive object - in this case a planet and its star - to bend light and act as a magnifying lens, as predicted by Einstein’s general theory of relativity.Īstronomers from two groups - Microlensing Observations in Astrophysics, based in New Zealand and Japan, and the Optical Gravitational Lensing Experiment, based in Poland and Chile - monitor the light from a vast field of background stars, looking for brief blips of increased brightness caused by a planet and its host star passing in the foreground. The new work was done using a method known as gravitational microlensing, which is more sensitive to planets farther out. “The implications of this discovery are profound,” wrote Joachim Wambsganss, of Heidelberg University in Germany, in an accompanying commentary in Nature. Now it seems as if the planets outnumber the stars. Before this research, it was thought that only about 10 or 20 percent of stars harbored Jupiter-mass planets. “It’s a bit of a surprise,” said David Bennett, a Notre Dame astronomer who was part of the team. There are two Jupiter-mass planets floating around for each of the 200 billion stars in the Milky Way galaxy, according to measurements and calculations by an international group of astronomers led by Takahiro Sumi, of Osaka University in Japan, and reported in the journal Nature. Astronomers said Wednesday that space was littered with hundreds of billions of planets that had been ejected from the planetary systems that gave them birth and either were going their own lonely ways or were only distantly bound to stars at least 10 times as far away as the Sun is from the Earth.
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