Observations

Orbiting Observatory Observations

Black hole candidates--phenomena exhibiting black hole effects--have been discovered and studied through such NASA satellites as the Small Astronomy Satellites (SAS) and the much larger Orbiting Astronomical Observatories (OAO) and High Energy Astronomical Observatories (HEAO).

The most likely candidate is Cygnus X-1, an invisible object in the constellation Cygnus, the swan. Cygnus X-1 means that it is the first X-ray source discovered in Cygnus. X-rays from the invisible object have characteristics like those predicted from material as it falls toward a black hole.

The material is apparently being pulled from the hole's binary companion, a large star of about 30 solar masses. Based upon the black hole's gravitational effects on the visible star, the hole's mass is estimated to be about six times of our Sun.

In time the gargantuan visible star could also collapse into a neutron star or black hole or be pulled piece by piece into the existing black hole, significantly enlarging the hole's event horizon.