Our galaxy's center region is producing gamma rays, but astronomers are still debating whether pulsars or dark matter are the source. Three recent studies tackle the debate head-on.
Hubble has spotted more than 100 small, faint galaxies in the young universe, common as dust bunnies but previously out of reach of even the best telescopes.
Observations of lensed quasars suggest the universe is expanding more quickly than we thought. But they contradict what we know about the young universe.
Astronomers analyzing a new sky survey have found that the distribution of dark matter in the modern universe is smoother than predicted from observations of a far younger universe.