The planets in our Solar System have mass comparable to that of the rogue planets, but they do not have a star. Astronomers using data from several European Southern Observatory (ESO) telescopes and other facilities have just discovered at least 70 new rogue planets. This is the largest group of rogue planets ever discovered, an important step towards understanding the origins and features of the mysterious galactic nomads.
Nria Miret- Roig, an astronomer at the Laboratoire d'Astrophysique de Bordeaux, France and the University of Vienna, Austria, and the first author of the paper, said they did not know how many they would find.
It would be hard to image a rogue planet far away from a star. Miret- Roig and her team took advantage of the fact that the planets are still hot enough to glow in the few million years after they were formed. There are at least 70 new rogue planets with Jupiter's mass comparable to the ones found in the Upper Scorpius and Ophiuchus constellations.
The team used data from a number of telescopes on the ground and in space to spot so many rogue planets. "We measured the motions of millions of sources in a large area of the sky," says Miret- Roig. The faintest objects in this region are the rogue planets.
The team used a variety of telescopes, including the Very Large Telescope, the VISTA, the VLT Survey Telescope, and the MPG/ESO 2.2-metre telescope. The majority of our data comes from the observatory. The leader of the new research at the Laboratoire d'Astrophysique de Bordeaux, France, says that their wide field of view and unique sensitivity were keys to their success. We used tens of thousands of wide-field images from the facilities of the European Organization for Astronomy.
The data from the European Space Agency's Gaia satellite was used by the team to explore and understand the Universe.
There could be many more starless planets that we have yet to discover according to the study. There could be billions of free-floating giant planets without a host star.
Astronomers may find clues to how the rogue planets form. Some scientists believe that rogue planets can form from the collapse of a gas cloud that is too small to lead to a star, or that they could have been kicked out of their parent system. Which mechanism is more likely is not known.
The mystery of these nomadic planets will be unlocked by further advances in technology. The team hopes to continue to study them with the upcoming ELT, which is due to start observations later this decade. "These objects are extremely faint and little can be done to study them," says Bouy. The ELT will be crucial to gathering more information about the planets we have found.
There are notes.
The exact number of rogue planets found by the team is hard to pin down because the observations don't allow the researchers to measure the mass of the probed objects. The count cannot include objects with a mass greater than 13 times Jupiter's mass. Since the team didn't have values for the mass, they had to rely on studying the planets' brightness to limit the number of rogue planets observed. The age of the planets itself is related to the brightness of the planet, as the older the planet, the less brightness it will have. If the region is young, the bright objects in the sample are likely below 13 Jupiter mass. The method gives a rogue planet count of between 70 and 170.
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