Orphan Worlds: Astronomers Discover Over 70 Jupiter-Sized Planets Wandering in Space
An artist’s impression of a free-floating planet.
(NOIRLab/NSF/AURA/J. da Silva)
Our universe is home to approximately 200 billion trillion stars, and most of them are believed to have planets. In fact, planets are byproducts of the star formation process, as they are made of the protoplanetary disks that form around stars during their creation.
While most planets’ lives revolve around their parent stars (quite literally!), some planets do end up getting ejected from their solar systems, effectively becoming rogue planets. However, there also exist some stars that wander in space like lost souls, without a parent star in sight.
Now, in an amazing discovery, astronomers have found at least 70 and as many as 170 such free-floating planets in a nearby region of the Milky Way, roughly tripling the total number of such planets known to date. In fact, this is the largest sample of such ‘orphan’ planets found in a single group.
These worlds have the same size as Jupiter, but are 13 times less massive than the gas giant of our solar system. They were found in the Upper Scorpius OB stellar association, which is 420 light-years away from Earth and the nearest star-forming zone to the Sun.
Instead of being gravitationally associated with a star, these planets seem to be moving by interacting among themselves!
They were spotted by a team of astronomers led by the study’s first author, Núria Miret-Roig of the Laboratoire d’Astrophysique de Bordeaux, at the University of Bordeaux in France. They used observations and archival data from a number of large observatories, which amount to 80,000 wide-field shots from more than 20 years of observations.
As these planets lurked far away from any illuminating stars, they would have been impossible to image. However, Miret-Roig and her team took advantage of these orphans being ‘young’—as they were only a few million years old, they were still hot enough to glow, which made them directly detectable by sensitive cameras on large telescopes.
With no star around, their origin still remains a mystery. While some scientists believe they may have been expelled from their parent system, others think they could be a result of the collapse of a gas cloud too tiny to produce a star.
However, if the former ejection model is to be believed, it would indicate that along with these free-floating Jupiter-mass planets—which are the most difficult to eject given their massive nature—there could be an even greater number of free-floating Earth-sized worlds wandering in the galaxy.
And with the Vera C. Rubin Observatory set to begin its scientific operations this decade, it would soon become possible to find more such free-floating planets and improve our understanding of these rogue orphans.
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