Lost in Space: Rogue Planet Spotted?


Astronomers using the European Southern Observatory (ESO) Very Large Telescope (VLT) and the Canada-France-Hawaii Telescope have identified a body that is likely a wandering planet without a mother star. It is the most exciting candidate planet to date and the closest object to the solar system at a distance of about 100 light years. Its relative proximity and the absence of a bright star nearby allowed the team to study its atmosphere in detail. This object also gives astronomers insight into the exoplanets that future instruments aim to image around stars other than the Sun.

Floating planets are objects of planetary mass that roam space without any connection to a star. Possible examples of such objects have already been found, but without knowing their age, it was not possible for astronomers to know if they were really planets or brown dwarfs – “failed” stars that did not exist. lack the mass to trigger the reactions that make the stars shine.

But astronomers have now discovered an object, called CFBDSIR2149, which appears to be part of a nearby stream of young stars known as the AB Doradus Moving Group. Researchers found the object in observations from the Canada-France-Hawaii Telescope and harnessed the power of ESO’s VLT to examine its properties.

The AB Doradus Moving Group is the closest group to the solar system. Its stars are drifting together in space and are said to have formed at the same time. If the object is associated with this moving group – and it is a young object – much more can be deduced about it, including its temperature, mass, and the composition of its atmosphere. There remains a low probability that the association with the moving group is fortuitous.

The connection between the new object and the moving group is the essential clue that allows astronomers to find the age of the newly discovered object. It is the first isolated planetary mass object ever to be identified in a moving group, and association with this group makes it the most interesting candidate floating planet identified to date.

“Searching for planets around their stars is like studying a firefly sitting 1 centimeter from a distant and powerful car headlight,” said Philippe Delorme of the Institut de Planétologie et d’Astrophysique de Grenoble and the CNRS University. / Joseph de Fourier, in France. “This nearby floating object provided the opportunity to study the firefly in detail without the car’s dazzling lights spoiling everything.”

Floating objects like CFBDSIR2149 are believed to form either as normal planets that have been started out of their home systems, or as isolated objects like smaller stars or brown dwarfs. Either way, these objects are intriguing – either as starless planets or as the smallest possible objects in a range from the most massive stars to the smallest brown dwarfs.

“These objects are important because they can either help us better understand how planets can be ejected from planetary systems or how very light objects can result from the process of star formation,” Delorme said. “If this tiny object is a planet that has been ejected from its native system, it conjures up the vivid image of orphan worlds drifting in the void of space.”

These worlds could be common, perhaps as numerous as normal stars. If CFBDSIR2149 is not associated with the AB Doradus moving group, it is more difficult to be sure of its nature and properties, and it can instead be characterized as a small brown dwarf. Both scenarios represent important questions about how planets and stars form and behave.

“Further work should confirm that CFBDSIR2149 is a floating planet,” Delorme said. “This object could be used as a reference to understand the physics of all similar exoplanets discovered by future special high contrast imaging systems, including the SPHERE instrument that will be installed on the VLT.”


Arline J. Mercier