Two dwarf galaxies (top and bottom) orbit the much larger Andromeda galaxy. DAVID DAYAG/WIKIMEDIA COMMONS ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ When astronomers fret about the “missing satellites problem,” they’re not talking about spacecraft in Earth orbit. Their problem is much bigger: For decades, far fewer dwarf galaxies have been seen orbiting the Milky Way and other large galaxies than predicted by models of galaxy formation. But now, two groups of astronomers have found evidence for not just a sufficient number of satellite galaxies to satisfy the simulations—but too many. “Maybe we’ve oversolved the problem,” says Marcel Pawlowski, an astronomer at the Leibniz Institute for...
