An almost invisible galaxy weighs as much as our own.
The Milky Way’s dark twin revealed : Nature News & Comment
http://www.nature.com/news/the-milky-way-s-dark-twin-revealed-1.20333
It took 33.5 hours on one of the world’s largest telescopes, but for the first time astronomers have measured the motion of stars inside a newly
recognized breed of dimly lit galaxy. The stars’ rapid speed reveals that the galaxy weighs as much as the far more brilliant Milky Way1.
“It’s an important measurement,” says Avi Loeb, chair of the astronomy department at Harvard University in Cambridge, Massachusetts, who was not
involved in the study. “It’s a very challenging measurement, and they should be saluted for getting it.”
‘Ultradiffuse’ galaxies came to attention only last year, after Pieter van Dokkum of Yale University in New Haven, Connecticut, and Roberto Abraham
of the University of Toronto in Canada built an array of sensitive telephoto lenses named Dragonfly. The astronomers and their colleagues observed
the Coma galaxy cluster 101 megaparsecs (330 million light years) away and detected 47 faint smudges.