An artist's impression of a gamma-ray burst, a powerful jet of energy lasting from less than a second to several minutes. The most powerful events in the universe, they are thought to be mostly associated with the explosion of stars that collapse into black holes. A. Roquette/ESO hide caption

itoggle caption A. Roquette/ESO

This image of the galaxy cluster Abell 520 — 2.4 billion light-years away — may challenge some of our basic theories about Dark Matter. It is overlaid with false-color maps showing concentrations of starlight (orange), hot gas (green) and mass (blue). The mass is mostly Dark Matter. M.J. Jee and A. Mahdavi/NASA/ESA/CFHT/CXO hide caption

itoggle caption M.J. Jee and A. Mahdavi/NASA/ESA/CFHT/CXO

The Warp in this Spiral Galaxy was probably the result of a cosmic collision with another galaxy. Hubble Heritage Team (STScI/AURA), C. Conselice (U. Wisconsin/STScI) et al., NASA hide caption

itoggle caption Hubble Heritage Team (STScI/AURA), C. Conselice (U. Wisconsin/STScI) et al., NASA