Mystery behind x-ray light from black holes solved

PTI | Jun 15, 2013, 06.29 PM IST

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WASHINGTON: Scientists claim to have solved the mystery how black holesproduce so many high-power X-rays. 

In a new study, astrophysicists from The Johns Hopkins University, NASA and the Rochester Institute of Technology conducted research that bridges the gap between theory and observation by demonstrating that gas spiralling toward a black hole inevitably results in X-ray emissions. 

The study states that as gas spirals toward a black hole through a formation called an accretion disk, it heats up to roughly 10 million degrees celsius. 

The temperature in the main body of the disk is roughly 2,000 times hotter than the sun and emits low-energy or "soft" X-rays. However, observations also detect "hard" X-rays which produce up to 100 times higher energy levels. 

Julian Krolik, professor of physics and astronomy in the Zanvyl Krieger School of Arts and Sciences, and his fellow scientists used a combination of supercomputer simulations and traditional hand-written calculations to uncover their findings. 

Supported by 40 years of theoretical progress, the team showed for the first time that high-energy light emission is not only possible, but is an inevitable outcome of gas being drawn into a black hole. 

"Black holes are truly exotic, with extraordinarily high temperatures, incredibly rapid motions and gravity exhibiting the full weirdness of general relativity," Krolik said. 

"But our calculations show we can understand a lot about them using only standard physics principles," Krolik said. 

As the quality and quantity of the high-energy light observations improved over the years, evidence mounted showing that photons must be created in a hot, tenuous region called the corona. 

This corona, boiling violently above the comparatively cool disk, is similar to the corona surrounding the sun, which is responsible for much of the ultra-violet and X-ray luminosity seen in the solar spectrum, researchers said.

Med-diet good for older adults: Study

The MeDiet is characterised by a high consumption of fruits, vegetables, legumes, olive oil, nuts, and whole grain; a moderate consumption of wine, dairy products, and poultry, and a low consumption of red meat, sweet beverages, creams, and pastries.
Due to its antioxidant and anti-inflammatory properties, the MeDiet might play a role in decreasing SUV concentrations.
 Reversion of hyperuricemia was achieved by adherence to the MeDiet alone, without weight loss or changes to physical activity, researchers said.

Map signals existence of other universes

LONDON: Scientists believe they have for the first time found evidence of the existence of other universes by analyzing data gathered by the European Space Agency's Planck spacecraft.
Theories that our universe could be just one of billions  or perhaps an infinite number  have been discussed for decades but until now, they have not been backed by any evidence.


However, a few weeks ago, scientists published a new map of the cosmic microwave background — the 'radiation' left behind after the Big Bang that created the universe 13.8 billion years ago. The map, based on the Planck's data, showed anomalies in the background radiation that, some experts say, could only have been caused by the gravitational pull of other universes outside our own.
"These anomalies are the first hard evidence for the existence of other universes that we have seen,, " said Laura Mersini-Houghton , a theoretical physicist at the University of North Carolina at Chapel Hill. Mersini-Houghton and her colleague Richard Holman at Carnegie Mellon University published a series of papers from 2005 onwards predicting what Planck would see. In particular, they claimed that the ancient radiation permeating our universe would show anomalies generated by the pull from other universes . The scientists analyzing the Planck data have now published a paper acknowledging the anomalies exist and cannot be explained by conventional means.
"It may be that the statistical anomalies described in this paper are a hint of more profound physical phenomena that are yet to be revealed," it said.
Planck gathered radiation from when the universe was just 3,70,000 years old — still glowing from the Big Bang. Planck's data showed the radiation is stronger in one half of the sky than the other. There is also a large 'cold' spot where the temperature is below average.