There is a graveyard of lost souls in Interstellar space. These planets float in the dark like ghost ships.
It takes patience and a good eye to catch sight of one. The European Southern Observatory's facilities have collected tens of thousands of images and have identified as many as 170 potential 'rogue' worlds.
It would suggest the Milky Way is home to many planets if a good number are confirmed to be planets.
There could be billions of giant planets in the sky without a host star.
Some of the clouds of gas and dust that give rise to a typical solar system may be too small for a star to form.
It's hard to say how many virgin births are created without a star in sight and how many are kicked out of their nest. We don't have enough information.
Being planets, they don't have the same glow as a star. They don't follow an Orbital path that would identify them as an exoplanet.
Most suspects have been glimpsed indirectly as a result of their massive bodies briefly distorting the background of starlight, a method that usually doesn't lend itself to a second look.
We need a large sample of rogues to track and analyze.
Astronomers took advantage of the fact newborn planets continue to glow with residual heat for millions of years.
They were able to find a huge list of candidate 'free-floating planets' within the Upper Scorpius and Ophiuchus constellations by scanning for this weak radiation signature.
Nria Miret-Roig is an astronomer at the Laboratoire d'Astrophysique de Bordeaux.
The faintest objects in this region are the rogue planets.
It's not likely that all will be planets. Only a few of the 170 signatures might qualify.
It's harder to estimate the mass of a planet from the light alone than it is from a star being tugged by a heavy companion.
A bigger rogue could be a brighter one. It could be a sign that it's been baked.
Some candidates could still be big enough to qualify as a low mass star if they were found in the same region of space.
The success of the technique puts us on a path to better understand the origins of these potential dark nomads.
The density of the rogues alone suggests that the isolated core collapse model can't be the only way to produce them.
We're on the verge of a new generation of space-watching technology which should help us expand our knowledge on such elusive objects, potentially allowing us to study their fates as well as their past.
"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 rogue planets we have found.
Nature Astronomy published this research.
