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HindustanTimes Wed,17 Sep 2014

City-based scientist duo cracks celestial mystery

Joydeep Thakur, Hindustan Times  Kolkata, February 02, 2013
First Published: 13:46 IST(2/2/2013) | Last Updated: 13:50 IST(2/2/2013)

Two city-based scientists have for the first time unravelled the mystery behind the feeding habits of Black Holes - a region in space that is said to have the strongest appetite in the entire universe.

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While the black holes are known to feed on any kind of matter, the majority of food supply comes from its companion star that is torn apart by the black hole due to its tidal force-the same which causes the rise of the Earth’s ocean surface on account of the gravitational pull of the Sun and Moon.

“Till date, it was thought that black holes feed on this ‘cold’ matter with a temperature of around ten million degree Celsius. This matter obeys Kepler’s laws-the laws guiding planets orbiting the Sun,” Sandip Kumar Chakrabarti, senior professor and head of the department of Astrophysics and Cosmology at SN Bose National Centre for Basic Sciences in Kolkata, told HT.

The matter slows down during its long travel time from the companion at a rate of around 10 km per second. Thus, the slow moving matter, mostly protons and electrons, cover nearly 1 million km in about a day.

However, with the benefit of satellites, scientists observed very high-energy photons-particles that make up light, coming out from regions close to the black holes. The high energy X-rays and Gamma rays cannot have its origins in the cold food, contend celestial experts.

“Scientists and celestial experts believe that over the last couple of decades there must be hot electron clouds somewhere nearby that has been feeding the energy to low-energy photons emitted by the cold food, but the actual location eluded them,” Chakrabarti said.

This mysterious cloud was named Compton Cloud after US Nobel Laureate Arthur Holy Compton, who discovered how energy is exchanged between electrons and photons.

Teaming up with one of his students Kinshuk Giri, Chakrabarti not only cracked the mystery surrounding the Compton Cloud, but also revealed that just as us Earthlings on an eatout order starters before digging into the main course, black holes too have a two-course meal-one being cold and the other being the steaming hot Compton cloud.

“One is a low calorie dish-rich in low energy photons, and the other stuffed with high calories has a potent mix of a billion degree of hot proton and electron.

The black holes feed on both in much the same way as dipping a cold, sugar-free biscuit in a glass of thick, steaming hot chocolate,” Chakrabarti said.

Their research findings are currently in the process of being published in a series of articles in the prestigious British journal of the Royal Astronomical Society. The findings would feature in the journal’s latest issue due out in February.

Unlike the slow motion of the first course, which lends to the cooling effect and a known commodity to expert sky gazers, the ‘main course’ closes in on the black hole at a frenetic pace owing its low rate of rotation. It consumes a million kilometres in about an hour till it is barely a 100 km from the black hole.

After a strenuous research spanning four years, Chakrabarti and Giri found that the fast moving matter meets a strong, centrifugal force, slowing it down and generating a huge volume of heat energy.

“The hot gun powder turns the low energy photons into high energy variants in the first course, which are then radiated in all directions. These had been long been eluding the scientists before being picked up by satellites,” Chakrabarti said.

Chakrabarti touched off the debate on a two-course meal almost 17 years back along with Russian mathematician Lev Titarchuk.

“Our new research shows that the two-course meal is not only possible, but has to be a universal rule supported by robust mathematics. Only this picture allows us to interpret the observed data satisfactorily,” Chakrabarti said.


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