Glowing black holes and Professor Hawking | The Daily Star
11:00 PM, November 16, 2009 / LAST MODIFIED: 11:00 PM, November 16, 2009

Glowing black holes and Professor Hawking

A black hole guzzles gas like a pig at a trough. It emits bursts of electromagnetic energy, which illuminate the entire scene.

BLACK holes are black because they eat up even the light that comes out of the matter being crushed into nothingness under its fearsome gravitational pull. However, it is from their pull on other objects outside them that black holes' presence can be known. While black holes themselves are invisible, their surroundings are dominated by powerful magnetic and gravitational forces. Those forces produce extremely bright radiations. Those radiations include cosmic rays, plasma jets and gamma-ray bursts that travel across the universe. It is very recently that scientists have started to unlock the mysteries of how those radiations are generated.
Earlier in 1974, it was the British theoretical physicist William Stephen Hawking (a man crippled by a rare degenerative motor neuron disease), who for the first time showed that black holes can emit radiation. But before he came into the scene, the general belief among the scientific community was that black holes cannot radiate any energy as they are the ultimate end of a star with masses greater than that of the sun. Due to huge mass, a black hole's force of degeneracy fails and gravitational force exerts its overwhelming force triggering a sudden collapse of the star.
Through its strong gravitational effect on nearby stars, a black hole can be located. In our galaxy a black hole which is six times bigger than the sun has been detected near the Signus X-1 stellar area. Due to quantum fluctuations near its 'event-horizon,' the boundary line of a black hole, virtual particles like gravitons (hypothetical particle of gravitation) or photon (light particles) collide with each other resulting in creation of real particles and emitting radiation. It is called Hawking Radiation. From the 'event-horizon' of a black hole, no event can be signalled. The hypothetical graviton has zero mass and can fly at the speed of light. A photon is an indivisible electromagnetic radiation having zero mass. Due to black hole's immense power, imaginary particles entering its abyss of void become real particles. However, inclusion of gravitation in the remaining forces of the universe is yet to be solved. Following emission of radiation, a black hole sometimes may lose its mass. However, its ultimate fate is not known. It is believed that a situation similar to the black holes existed in the early stages of the universe when it was creation from the Big Bang. Hawking says we may not find a unified role at all still it is imperative to try for it.

The writer is former senior Scientific officer, BCSIR.

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