Gamma-ray beams seen in the Milky Way's central black hole suggest that the galaxy's center was much more active in the past, according to new research.

WASHINGTON, April 12, 2012 /PRNewswire-USNewswire/ -- Astronomers are actively hunting a class of supermassive black holes throughout the universe called blazars thanks to data collected by

There's more to the cosmos than meets the eye. About 80 percent of the matter in the universe is invisible to telescopes, yet its gravitational influence is manifest in the orbital speeds of stars around galaxies and in the motions of clusters of galaxies.

The human eye is crucial to astronomy. Without the ability to see, the luminous universe of stars, planets and galaxies would be closed to us, unknown forever. Nevertheless, astronomers cannot shake their fascination with the invisible.

Detectable for only a few seconds but possessing enormous energy, gamma-ray bursts are difficult to capture because their energy does not penetrate the Earth's atmosphere.