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Dozens of free-floating planets found in the Milky Way

By using telescope observations and archival data, a research team led by the University of Bordeaux has recently found more than 70 free-floating planets – astronomical bodies wandering through space without orbiting a parent star – in a nearby region of the Milky Way. This is the largest sample of such planets found in a single group and it nearly doubles the overall number of this type of planets known to scientists.

These free-floating planets with sizes close to that of Jupiter are located in the Upper Scorpius OB stellar association, an area of the Milky Way which is 420 light-years away from the Earth. This stellar association contains several of the most famous nebulae, such as the Rho Ophiuchi cloud, the Pipe Nebula, the Coalsack, and Barnard 68.

Free-floating planets have mostly been discovered through microlensing surveys, in which astronomers look for brief chance alignments between exoplanets and background stars. However, since microlensing events happen only once, follow-up observations are impossible.

The new planets were discovered through a different method. Since million years after their formation, they are still hot enough to glow, the scientists detected them by using highly sensitive cameras on the world’s largest and most performant telescopes.

“We measured the tiny motions, the colors and luminosities of tens of millions of sources in a large area of the sky,” explained study lead author Núria Miret-Roig, an astrophysicist at the University of Bordeaux. “These measurements allowed us to securely identify the faintest objects in this region.” 

“The treasure trove available in the NOIRLab Astro Data Archive has been fundamental to this study,” added project leader Hervé Bouy, an astronomer at the same university. “We needed very deep and wide-field images in both the optical and near-infrared, spanning a long time baseline. So the Dark Energy Camera and NEWFIRM were very appealing for our project because they are among the most sensitive wide-field cameras in the world.”

The researchers believe that the free-floating planets may have been ejected from their parent system millions of years ago. If this hypothesis is correct, there could be even more Earth-sized free-floating planets waiting to be discovered. “The free-floating Jupiter-mass planets are the most difficult to eject, meaning that there might even be more free-floating Earth-mass planets wandering the galaxy,” said Miret-Roig.

The study is published in the journal Nature Astronomy

By Andrei Ionescu, Staff Writer

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