Black Hole
A black hole is an astronomical object whose gravity is so strong that nothing—even light—can escape from within its event horizon. It forms when a massive star’s core collapses or through other processes, and may have an accretion disk of infalling matter that emits radiation. Supermassive black holes at galaxy centers influence stellar orbits, and mergers produce gravitational waves.
Source: nasa.gov
APODs including "Black Hole"
A Year of Resolving Backgrounds
30/12/2000
No matter which direction you look, no matter what type of light you see, the sky glows - but why? The sources of many of these background radiations have remained long-standing puzzles, but this millennial year brought some partial resolutions. In X-ray light the recently launched spacecraft Chandra and XMM resolved much of the seemingly uniform X-ray background into many discrete sources, many of which appear to be black holes at the centers of galaxies accreting matter. In microwave light, the BOOMERANG and MAXIMA-1 missions resolved with new clarity the seemingly uniform microwave background. The size and distribution of these spots indicates a geometrically flat universe, which, when combined recent supernovae results, indicate a universe with an accelerating expansion rate filled with dark matter and dark energy. Pictured above, a map spanning ten degrees of the microwave sky resolves the microwave background into hot and cold spots, as indicated in microkelvins.