Back in 2016, researchers claimed to have found a galaxy made almost completely of dark matter. Now that claim has fallen apart. The galaxy, Dragonfly 44 (DF44), belongs to a class of mysterious objects known as ultra-diffuse galaxies, or UDGs. Researchers have debated since the 1980s whether these vast, dim objects have a low mass, like dwarf galaxies smeared across huge reaches of space, or are heavy, Milky Way-style galaxies that seem dim for two reasons: because they have almost no stars, and because a huge fraction of their mass is dark matter found in the outer fringes of the galaxy in so-called dark matter haloes that emit no light. In a paper published in 2016 in the Astrophysical Journal Letters, scientists argued that DF44 was one of these galaxies with a big dark matter halo and few stars. They estimated its mass and found it was at least 98 per cent dark matter.
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"We knew that this would be a historic comet"
Astronomer David Levy was immortalised for his co-discovery of Comet Shoemaker-Levy 9 â its impact with Jupiter 29 years ago held the world in awe
CELESTRON STARSENSE EXPLORER DX 102AZ
Innovative technology provides the simplest and quickest solution yet to finding objects to observe, and this instrument will be very popular with beginners
MOON TOUR - COPERNICUS
Get up close to the âMonarch of the Moonâ
A HUNGRY BLACK HOLE 'SWITCHES ON' AS ASTRONOMERS WATCH IN SURPRISE
J221951 is one of the most extreme examples yet
MYSTERIES OF THE UNIVERSE - WHY DOES JUPITER CHANGE COLOUR?
For years, scientists have tried to work out why Jupiterâs bands frequently move and change colour. Now they believe theyâve found the answer
MARS HELICOPTER PHONES HOME AFTER A 63-DAY SILENCE
Rugged terrain had kept Ingenuity from communicating with its robotic partner, the Perseverance rover
SIX OF THE BEST SPACE PRANKS
It turns out that the sky isnât the limit when it comes to a good old-fashioned practical joke
CLIMATES CHANGE IN THE SOLAR SYSTEM
Alongside Earth, our planetary neighbourhood is changing. But not for the betterâŠ
TIME APPEARED TO MOVE FIVE TIMES SLOWER IN THE FIRST BILLION YEARS AFTER THE BIG BANG
Time dilation, brought about by the relativistic expansion of space, has resulted in the observed slowing of âclocksâ in the early universe
WHAT CAN WE DO WITH A CAPTURED ASTEROID?
Asteroids could provide us with rare resources