An international team of astronomers has discovered a massive galaxy that consists of 99.99 percent dark matter. Even though it is relatively nearby, astronomers had missed the galaxy, named Dragonfly 44, for decades because it is very dim. The galaxy lies about 300 million light-years away in the constellation Coma.
A team of scientists has documented atmospheric changes on Io, Jupiter’s volcanically active satellite, as the giant planet casts its shadow over the moon during daily eclipses. Io’s thin atmosphere collapses as the sulfur dioxide gas emitted from volcanoes freezes when shaded by Jupiter. The atmosphere reforms when Io moves out of eclipse and the ice sublimates.
Since its detection in 2014, the brown dwarf known as WISE 0855 has fascinated astronomers. Only 7.2 light-years from Earth, it is the coldest known object outside of our solar system. Now, a team led by astronomers has succeeded in obtaining strong evidence for the existence of clouds of water or water ice — the first such clouds detected outside our solar system.
The placid appearance of NGC 4889 can fool the unsuspecting observer. But the elliptical galaxy, pictured here in front of hundreds of background galaxies, and deeply embedded within the Coma galaxy cluster in this new image from the NASA/ESA Hubble Space Telescope, harbours a dark secret. At its heart lurks one of the most massive black holes ever discovered.