What is a Black Hole in space?

Term coined by John A. Wheeler for an object so compact that nothing, not even light, can escape its gravitational attraction.

Although the discussions of the capture of light by massive objects can be dated to John Mitchell and Pierre Simon Laplace in the eighteenth century, a proper understanding lies in the realms of general relativity theory.

Karl Schwarzschild calculated the boundary radius or event horizon, of such a theoretical (nonrotating) body to be about 3 km for a body of one solar mass.

Interior to the event horizon relativity theory suggests that any matter collapse into an infinitesimally small volume or singularity.

In 1963, a solution for a rotating object was provided by Robert P. Kerr. Stephen W. Hawking in the 1970s applied quantum mechanical concepts to the theory of black holes to show that they may not exist forever but can radiate energy.

To address the physical origin for black holes, J. Robert Oppenheimer and Hartman Snyder in 1939 first considered the collapse of a star.

Modern astronomy inquiry identifies two observational classes or black holes candidates, stellar black holes in X-ray binary systems and massive black holes on the nuclei of galaxies.

A dozen or more black hole candidates are known, including Cygnus X-1 and ScorpionX-1. The second category, a few million to a few billion solar masses, is postulated as the central engine responsible for a wide range of energetic phenomena (radio, X-ray, and gamma-ray emission, jets and others) associated with the nuclei of some galaxies.

Such active galactic nuclei objects include Seyfert galaxies, radio lobe galaxies, and quasars. Massive black holes also may be present in the centers of some nonactive galaxies.
What is a Black Hole in space?

The Hubble Space Telescope

The Hubble Space Telescope
Initial discussion of an orbiting telescope, led by Lyman Spitzer and Leo Goldberg in the late 1940s, generally met with little enthusiasms.

Ground based astronomy remained more attractive to most astronomers, as shown by the national observatory campaign of the next decade.

During the 1960s, however, NASA’s Orbiting Astronomical Observatories program rekindled interest in the concept and led to suggestions for a federally funded Large Space Telescope with a 3-meter mirror.

The telescope soon became linked with the proposed space shuttle as an important payload and as a target for later maintenance missions.

As part of a continuous concern with the costs, astronomers joined NASA officials to redraft plans for the instrument during the 1970s, ultimately decreasing the mirror size to 2.4 meters and minimizing scientific goals in favor a program design that congress would accept.

The instrument proved much more difficult to design than originally thought, leading to higher costs, further modifications and a complete management shake-up in 1983.

The successful launch of the telescope in April 1990 appeared to justify the $1.6 billion project costs (more than four times the original estimate), but the instrument soon proved seriously flawed. The main mirror had been ground to the wrong figure, making precise focusing impossible.

The NASA review panel report, issued in November, concluded that inadequate testing procedures had led to the misshapen mirror.

The scientific rewards that Hubble Space Telescope promised are at hand. In 1996, Hubble Space Telescope took its 100,000 exposure – a milestone that some thought would never come.

The newly improved telescope is often more productive than the most productive ground based telescope with which it works.

With proper care and maintenance, it could last well into the first decades of the 21st century.
The Hubble Space Telescope