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Some Planets Really Are Alien Invaders
by Ken Crosswell
Some people reach for the stars, but the stars themselves seem to be reaching for the planets. Although Earth and its planetary neighbors were born with the sun, a new study says billions of stars in our galaxy likely grabbed planets from the depths of space. The finding may explain the puzzling presence of worlds located far from their suns and even suggests that our solar system could harbor a planet that lurks unseen well beyond Pluto.
Planets form from a disk of gas and dust orbiting a star and so should not exist beyond the disk’s edge. In recent years, however, astronomers have reported giant planets more than 100 sun-Earth distances from their stars—much farther out than Pluto, whose mean distance from the sun is 39.5 times greater than Earth’s.
Now astronomers Hagai Perets of the Harvard-Smithsonian Center for Astrophysics in Cambridge, Massachusetts, and Thijs Kouwenhoven of the Kavli Institute for Astronomy and Astrophysics at Peking University in China say the far-out planets once roamed space free of any star, but they came in from the cold when their newfound suns captured them. Such free-floating planets arise when other planets kick them out of their homes; astronomers can detect them because their gravity magnifies the light of more distant stars. These observations suggest free-floating planets are roughly as abundant as stars…
(read more: Science NOW)
(image: David Lafrenière, et al./Gemini Observatory)

Some Planets Really Are Alien Invaders

by Ken Crosswell

Some people reach for the stars, but the stars themselves seem to be reaching for the planets. Although Earth and its planetary neighbors were born with the sun, a new study says billions of stars in our galaxy likely grabbed planets from the depths of space. The finding may explain the puzzling presence of worlds located far from their suns and even suggests that our solar system could harbor a planet that lurks unseen well beyond Pluto.

Planets form from a disk of gas and dust orbiting a star and so should not exist beyond the disk’s edge. In recent years, however, astronomers have reported giant planets more than 100 sun-Earth distances from their stars—much farther out than Pluto, whose mean distance from the sun is 39.5 times greater than Earth’s.

Now astronomers Hagai Perets of the Harvard-Smithsonian Center for Astrophysics in Cambridge, Massachusetts, and Thijs Kouwenhoven of the Kavli Institute for Astronomy and Astrophysics at Peking University in China say the far-out planets once roamed space free of any star, but they came in from the cold when their newfound suns captured them. Such free-floating planets arise when other planets kick them out of their homes; astronomers can detect them because their gravity magnifies the light of more distant stars. These observations suggest free-floating planets are roughly as abundant as stars…

(read more: Science NOW)

(image: David Lafrenière, et al./Gemini Observatory)