.A pair of strange new worlds that blur the boundaries between planets and stars have been discovered beyond our Solar System.
Dubbed "planemos", they circle each other rather than orbiting a star.
Their existence challenges current theories about the formation of planets and stars, astronomers report in the journal Science.
The pair belongs to what some astronomers believe is a new class of planet-like objects floating through space; so-called planetary mass objects, or "planemos", which are not bound to stars.
And while they have similar masses to many of the giant planets discovered beyond our Solar System (the largest weighs in at 14 times the mass of Jupiter and the other is about seven times more massive), they are not thought to be true planets either.
The two objects have similar spectra and colours, suggesting that they formed at the same time about a million years ago.
They are separated by about six times the distance between the Sun and Pluto, and can be found in the Ophiuchus star-forming region some 400 light years away. They go under the official name Oph 162225-240515, or Oph 1622 for short.
Oph 1622 was discovered using the ESO's New Technology Telescope at La Silla, Chile. Follow-up studies were conducted with the ESO's Very Large Telescope.