A 'ghost' galaxy made up almost entirely of dark matter has been discovered by scientists

Perseids meteor shower with the Milky Way

“We found many times more mass indicated by the motions of the stars than there is mass in the stars themselves.”

Without the extra gravity of dark matter binding it together, Dragonfly 44 would quickly fall apart.

The scientists, whose findings are published in the The Astrophysical Journal Letters, suspect there could be other dark matter galaxies waiting to be discovered.

Co-author Professor Roberto Abraham, from the University of Toronto in Canada, said: “We have no idea how galaxies like Dragonfly 44 could have formed.

“The data shows that a relatively large fraction of the stars is in the form of very compact clusters, and that is probably an important clue. But at the moment we’re just guessing.”

Dark matter is one of the great unsolved mysteries of the universe.

Scientists now know that only 5% of the interchangeable mass-energy in the universe is made up of “normal” matter that we can see and touch.

Dark matter, which exerts a gravitational pull, makes up 27%. It does not reflect light and cannot be detected directly by any means known to science. Despite a number of theories, the true nature of dark matter remains unknown.

The remaining 68% of the universe is made from something even more baffling, dark energy - a kind of anti-gravity force that appears to be repelling galaxies away from each other at an accelerating rate.

Dr Van Dokkum added: “This has big implications for the study of dark matter. Ultimately what we really want to learn is what dark matter is.

“The race is on to find massive dark galaxies that are even closer to us than Dragonfly 44, so we can look for feeble signals that may reveal a dark matter particle.”