![]() Some researchers believe that dark matter could be responsible for light halos around galaxies. New images from GMOS also revealed a halo of star clusters similar to the halo around the Milky Way. The dim, spheroidal galaxy looks a bit like a dirty smudge on a photo of deep space. Using the Gemini Multi-Object Spectrometer (GMOS), they created a color image of the galaxy. The team then went to the Gemini Observatory, also in Mauna Kea, to take new photos of Dragonfly 44. This finding opens up a whole new class of massive objects that we can study." A dirty smudge in space The only such galaxies we had to study before were tiny. "It helps to have objects that are almost entirely made of dark matter so we don't get confused by stars and all the other things that galaxies have. "This has big implications for the study of dark matter," van Dokkum said. Of all the stuff in this Milky Way-size galaxy, we can see almost nothing. But the other 99.99 percent of Dragonfly 44's mass is the ever-elusive dark matter. ![]() Only 0.01 percent of the galaxy is made of ordinary, visible matter: stuff that is made of atoms containing protons, neutrons and electrons. In other words, van Dokkum and his team found evidence of way more mass than they could actually see. So there was a huge discrepancy: using Keck Observatory, we found many times more mass indicated by the motions of the stars, than there is mass in the stars themselves.” In the Dragonfly galaxy stars move very fast. “They don’t care what form the matter is, they just tell you that it’s there. “Motions of the stars tell you how much matter there is," van Dokkum said in a statement. They used a tool on the Keck II telescope called the Deep Imaging Multi-Object Spectrograph (DEIMOS) to study the movement of stars in the galaxy. To investigate the amount of dark matter in Dragonfly 44, the team turned to one of the largest telescopes on Earth, located at the W. They suspected that dark matter was responsible for holding the galaxy together, and this particular galaxy seemed like it contained a ton of it, so they set out to determine exactly how much. There wouldn't be enough gravity, and the stars would drift apart. Van Dokkum and his team later realized that there was something very odd about Dragonfly 44: a galaxy that big couldn't possibly hold itself together with so few stars. While it's as big as the Milky Way, it only emits about 1 percent as much light. ![]() Dragonfly 44 was one of the largest and brightest galaxies they found. But no one had noticed these galaxies hiding in the dark before. This distance is easily close enough for a telescope to see the Hubble Space Telescope can see billions of light-years away. ĭragonfly 44 is one of 47 ultradiffuse, or "fluffy" galaxies that Pieter van Dokkum of Yale University and colleagues found in the Coma Cluster, a group of at least 1,000 galaxies around 300 million light-years from Earth. With a combination of eight telephoto lenses and cameras, the array is designed to look at objects in space that aren't bright enough to see with other telescopes. This dark galaxy, named Dragonfly 44, was first detected in 2015, through the use of the Dragonfly Telephoto Array in New Mexico. ![]() Whatever it may be, about 80 percent of the mass in the universe is dark matter. No one really knows what dark matter is made of, but scientists believe it exists because they can see the effects of its gravity on other things in space. The other 99.99 percent of the stuff in this galaxy can't be seen. Only one-hundredth of one percent of the galaxy is ordinary, visible matter like stars and planets. Astronomers have discovered a galaxy as big as the Milky Way that consists almost entirely of dark matter, a mysterious and invisible substance that scientists have been trying to figure out for decades. ![]()
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