Scottish astronomers have discovered planets that appear to have been formed without a parent star.
A dozen of the 'orphan' planets were found in a star-forming region called Rho Ophiuchus B, 500 light years away.
They show that planets can be spawned on their own from the same process that makes stars.
One of the planets, named Rho Ophiuchus B-11, has nine times the mass of Jupiter.
"It's a planet but it has all the hallmarks of an embryonic star," said Ms Jane Greaves from the Royal Observatory in Edinburgh, who helped make the discovery.
Until recently it was thought that planets could only form from gas and dust swirling in a disc around a newborn star. Then in 2000 astronomers spotted isolated planets in the Orionis Sigma star cluster. How they got there remained a mystery.
Rho Ophiuchus B-11 has now solved the puzzle. The astronomers saw evidence of fast streams of gas jetting from the planet's polar regions - a trait characteristic of forming stars.
"Though Rho Ophiuchus B-11 is planet-sized, it is in the process of condensing from an isolated gas cloud in exactly the same way as a young star," Ms Greaves told New Scientistmagazine.
The astronomers believe such orphan planets might be common in the galaxy. In fact, there could be as many lonely planets as there are stars.
PA