Their wide field of view and unique sensitivity were keys to our success,” explains Hervé Bouy. “The vast majority of our data comes from ESO observatories, which were absolutely critical for this study. The team of the COSMIC DANCE project used observations from several European Southern Observatory (ESO) telescopes located in Chile, along with NSF’s NOIRLab facilities, the Canada France Hawaii telescope and the Subaru telescope. “These measurements allowed us to securely identify the faintest objects in this region, the rogue planets.”
“We measured the tiny motions, the colours and luminosities of tens of millions of sources in a large area of the sky,” explains Núria Miret-Roig. To spot so many rogue planets, the astronomers used data spanning about 20 years from several telescopes on the ground and in space. They found at least 70 new rogue planets with masses comparable to Jupiter’s in a star-forming region close to our Sun, located within the Scorpius and Ophiuchus constellations. However, Núria Miret-Roig and her team took advantage of the fact that, in the few million years after their formation, these planets are still hot enough to glow, making them directly detectable by sensitive cameras on large telescopes. Rogue planets, lurking far away from any star illuminating them, would nor mally be impossible to image.
“We did not know how many to expect and are excited to have found so many,” says Núria Miret-Roig*, a postdoctoral researcher at the University of Vienna, Austria, who received her PhD from the University of Bordeaux, and is the first author of the new study published 22 December 2021 in the journal Nature Astronomy. This is the largest collection of rogue planets ever discovered, an important step towards understanding the origins and features of these mysterious galactic nomads. Not many were known until now, but the astronomers of the European project COSMIC DANCE, led by Hervé Bouy, a professor of the University of Bordeaux at the Laboratoire d’astrophysique de Bordeaux (LAB – CNRS and University of Bordeaux) have just discovered between 70 and 170 new rogue planets in the Milky Way. Rogue planets are elusive cosmic objects that have masses comparable to those of the planets in our Solar System but do not orbit a star, instead roaming freely on their own. Artist's impression of a free-floating planet lost in deep space © University of Bordeaux