The Swarm
28.01.2005

What do you call a group of black holes ... a flock, a brace, a swarm? Monitoring a region around the center of our Galaxy, astronomers have indeed found evidence for a surprisingly large number...

Black Holes Are Black
19.01.2001

Q: Why are black holes black? A: Because they have an event horizon. The event horizon is that one-way boundary predicted by general relativity beyond which nothing, not even light, can return. X-ray astronomers...

Microquasar in Motion
16.09.2004

Microquasars, bizarre binary star systems, generating high-energy radiation and blasting out jets of particles at nearly the speed of light, live in our Milky Way galaxy. The energetic microquasar systems seem to consist...

The Swarm
29.07.2006

What do you call a group of black holes ... a flock, a brace, a swarm? Monitoring a region around the center of our Galaxy, astronomers have indeed found evidence for a surprisingly large number...

N44C: A Nebular Mystery
14.05.2002

Why is N44C glowing so strangely? The star that appears to powers the nebula, although young and bright, does not seem hot enough to create some of the colors observed. A search for a hidden hotter star in X-rays has come up empty.

X Ray Moon and X Ray Star
9.09.2000

An x-ray star winks out behind the Moon in these before (left) and after views of a lunar occultation of the galactic x-ray source designated GX5-1. The false color images were made using data from the ROSAT (ROentgen SATellite), orbiting observatory.