Black Holes: - Black hole page from NASA's "Imagine the universe!" site; includes a section on observational aspects - "If We Can't See Them, How Do We Know They're There?.

Do Black Holes Exist?: - Brief text by Pablo G. Ostrov about the evidence for the existence of black holes, aimed at a general audience.

Field Guide to X-ray Sources: - Pages on the website of the Chandra X-Ray Observatory; includes information about stellar, mid-mass and supermassive black holes, Chandra images, and a podcast.

XMM: Black Holes and Quasars: - Educational pages on the website of the space-borne X-ray telescope XMM, hosted by the University of Birmingham. Information about black holes and other astronomical sources of X-rays.

Black Holes in Astrophysics: - Review article by Ramesh Narayan (Harvard-Smithsonian Center for Astrophysics) about the astrophysical evidence for black holes. (June 14, 2005)

The Afterglow of Massive Black Hole Coalescence: - Article by Milos Milosavljevic and Stearl Phinney; describes the kind of afterglow that should be visible for X-ray telescopes when two massive black holes merge. (March 14, 2005)

Radio Astronomers Lift 'Fog' on Milky Way's Dark Heart: - Press release by the National Radio Astronomy Observatory about observations of the immediate neighborhood of our galaxy's central supermassive black hole. (April 1, 2004)

Study of Accretion Processes on Black Holes: Fifty Years of Developments: - Review article by Sandip K. Chakrabarti of the research done on one of the main mechanisms by which black holes cause highly luminous phenomena in their immediate neighborhood. (February 24, 2004)

Detection of Hard X-ray Emission from the Galactic Nuclear Region with INTEGRAL: - Article by Guillaume Belanger and colleagues; recounts X-ray observations of the neighborhood of our galaxy's central black hole. (November 7, 2003)

Evidence for the Black Hole Event Horizon: - Review article by Ramesh Narayan about possible observational evidence for the defining feature of black holes. (October 23, 2003)

Closest Star Seen Orbiting the Supermassive Black Hole at the Centre of the Milky Way: - Article by R. Schodel and colleagues (Max Planck Institute for Extraterrestrial Physics) about the best evidence to date for the existence of a supermassive black hole in the center of our own galaxy - the way it influences the orbits of nearby stars. (October 18, 2002)

Astrophysical Evidence for the Existence of Black Holes: - Review article by Annalisa Celotti, John C. Miller, and Dennis W. Sciama (SISSA, Trieste) about the current state of the search for observational evidence for the existence of both stellar-mass and supermassive black holes. (December 9, 1999)

Hubble Space Telescope Discovers Disk Fueling Possible Black Hole: - News item published on the website of the Space Telescope Science Institute. (November 19, 1992)