Where we see black sky, astonomers see mass – but whats tipping the scales?
spiral-shaped galaxies. Now, however, an ordinary and long-neglected piece of the universe – the humble dwarf galaxy – promises rich insights into our place in the cosmos. “These common and durable galaxies are the cosmic equivalent of rocks,” says John “Jay”Gallagher III, a professor of astronomy and a current explorer of miniature galaxies. “There are 10 times as many dwarf galaxies as giants, but for the most part they’ve been ignored.” These galaxies, which contain just a million or so stars, have become important because they seem to be jam-packed with dark matter, the hypothesized missing mass of the universe. Astrophysicists have long been trying to account for the chunk of the universe’s supposed mass that does not exist as stars, planets or other directly detectable phenomena. In dwarf galaxies, they might have found it. “The smallest ones seem to be absolutely loaded with dark matter,” says Gallagher. Because dwarf galaxies have so few stars, they could easily be ripped apart
