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We may聽have just seen solid evidence for thousands of planets outside the Milky Way. It would be the first glimpse of planets outside our galaxy.

These traces were found with the help of gravitational lensing, which happens when an object magnifies the light of something more distant, making it appear larger to telescopes. The quasar RX J1131鈥�1231, a galactic nucleus surrounded by a ring of gas and dust, has a well observed rotation rate thanks to this effect. But the spectra of light emitted by the area around it seems to be shifting in small ways. So small and frequent, in fact, that it is unlikely to be caused by stars 鈥� which would cause a much larger redshift or blueshift.

and at the University of Oklahoma tried to measure the mass of what could be tugging on this quasar. 鈥淚f you use stars, it鈥檚 basically impossible. You have too much mass,鈥� says Guerras. 鈥淪o you need a lot of small objects.鈥� More massive objects would cause a few large disturbances, not many small ones.

Trillions of planets

Guerras and Dai think they are seeing the effect of around 2000 planets with masses between that of the moon and Jupiter. But they aren鈥檛 orbiting a star, like Earth is. These are planets that were flung out of their solar systems long ago, making them unattached planets

鈥淭he fraction of rogue planets per star [in the galaxy] estimated by this study makes sense to me, but it is subject to large observational errors,鈥� says at the University of Puerto Rico at Arecibo. He says those errors could be due to the light being distorted by smaller galaxies between us and this quasar.

The observed shift in light could be some innate part of the behaviour of the quasar, says Jonathan Lunine at Cornell University in New York. If it isn鈥檛, its galaxy as a whole could host a trillion planets.

Reference: Arxiv,

Read more: Hidden exoplanets could be revealed by echoing light

This article appeared in print under the headline 鈥淗ave we seen planets outside our galaxy?鈥�