Astronomers have spotted a large group of orphan planets: 170 candidates for such lonely worlds have been found in the Rho Cygnus cloud.
Planets are born close to young stars from the surrounding gas-dust cloud: this is usually where they stay. However, occasionally, a particular cataclysm may eject a planet from its home system and send it on an endless, lonely journey across the galaxy. It is assumed that something similar happened once in the Solar System, which lost one of its planets. In all, there must be billions of "orphan planets" in the Milky Way, although they are extremely difficult to spot, as they are no longer illuminated or warmed by the light of their mother star.
However, astronomers have recently spotted a large group of free-flying planets in the molecular cloud of the Ophiucus, a giant dark nebula 420 light years away, where active star formation is taking place. Scientists estimate that there are between 70 and 170 orphan planets the size of Jupiter alone. They write about it in an article published in the journal Nature Astronomy.
The authors of the paper analysed data from more than 20 years of observations by a number of ground-based telescopes (VLT, VST and others) as well as by the Gaia space observatory. "We measured the faint motions, colours and luminosities of tens of millions of sources over a wide area of the sky," says Núria Miret-Roig. - The data made it possible to identify the faintest objects in this area, the 'orphan planets'.
A total of about 170 candidates have been identified, of which at least 70 must be free-flying planets. It is not yet possible to be more precise, as the masses of the candidates have not been determined: the scientists were only guided by the brightness of the object's residual radiation. And this is not only related to its size, but also to its age: a similar signal can be received from a young, small orphan planet, and from an old, heavy brown dwarf, belonging to a completely different type of celestial body.
