Experts have long known that planets would not be confined to our galaxy, but this is the first time that a celestial body has been discovered outside of the Milky Way.

Researchers from the University of Oklahoma used microlensing – an astronomical phenomenon that allows scientists to use gravity from huge objects such as stars to peer hundreds of billions of lightyears into the universe – to detect the planets.

The scientists say they have detected up to 2,000 planets beyond the Milky Way, in a galaxy around 3.8 billion light years away from Earth and ranging in mass sizes from the moon to Jupiter.

University of Oklahoma researchers used NASA's Chandra X-ray observatory and were even able to see a quasar – a large celestial object – up to six billion lightyears away.