Some tightly-packed globular clusters show signs of unseen black holes affecting the movements of their stars. Astronomers are using the Hubble Space Telescope to look for evidence of such hidden monsters.
Galaxy clusters serve as gravitational zoom lenses for the Hubble Space Telescope, magnifying the light from more remote background galaxies to shed light on the nature of such lenses and the distribution of dark matter.
Messier 17 is a familiar target for amateur astronomers, an impressive nebula in even modest telescopes. But the Swan reveals its vast extent in a spectacular shot from the European Southern Observatory’s 2.2-metre La Silla telescope.