Using data from observations of ground-based and space telescopes for almost two decades, astronomers have discovered in the region of star formation close to us 70 planets freely wandering in space. The discovery of worlds not associated with any star is an important step towards understanding the origin and properties of these mysterious galactic wanderers. The results of the study are presented in the journal Nature Astronomy.
“There are probably far more elusive, lonely planets out there than we’ve been able to find so far. There may be several billion of them in the Milky Way, ”says Hervé Bui, co-author of the study at the Astrophysical Laboratory of Bordeaux (France).
Taking pictures of free-floating planets devoid of starlight is an almost impossible task, unless they have a large mass and have not cooled down since their formation, with a weak glow available to highly sensitive instruments. It is these gigantic young worlds with an age of only a few million years that were discovered when analyzing a huge set of observational data, including about 80 thousand images in the optical and infrared ranges.
“We measured the microscopic movements, colors and luminosities of tens of millions of sources over a large area of the sky. This allowed us to reliably identify the weakest objects in the area – roaming planets, ”explained Mirae-Roig, lead author of the study at the Bordeaux Astrophysical Laboratory.
Previously, wandering planets were only found using microlensing, in which astronomers observe a brief random alignment of such an object and a star in the background. At the same time, given that the event is no longer repeated, both further study and confirmation of the candidate are impossible.
By studying the discovered roaming planets, astronomers can find an explanation for how exactly these mysterious objects are formed. Some scientists believe they can form when clouds of gas are compressed, which are too small to form a star. For others, these planets were thrown out of the parent system. But which of the mechanisms is more likely remains unclear.
“The ejection model assumes that the number of free-floating planets the size of the Earth can be huge, since it is much more difficult to expel giant worlds with the mass of Jupiter from the system. Unfortunately, these objects are extremely faint, so little can be done with existing instruments to study them. The use of next-generation telescopes will be essential to gather more complete information on the population of roaming planets, ”concluded Mirae-Roig.