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Archive for the ‘Astronomy & Cosmology’ Category

Short Gamma-ray Bursts

For decades it was baffling. Out of the still night sky, astronomers peering through their telescopes would occasionally glimpse quick bursts of high-energy light popping off like flashbulbs at the far side of the universe.

These bursts seemed impossibly powerful: to appear so bright from so very far away, they must vastly outshine entire galaxies containing hundreds of billions of stars. These explosions, called gamma ray bursts (GRBs), are by far the brightest and most energetic phenomena in the known universe, second only to the Big Bang itself. Scientists were at a loss to imagine what could possibly cause them.

 

Read more at NASA website

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This week a paper puplished arxiv titled :Gravitational fields as generalized string models

We show that Einstein’s main equations for stationary axisymmetric fields in vacuum are equivalent to the motion equations for bosonic strings moving on a special nonflat background. This new representation is based on the analysis of generalized harmonic maps in which the metric of the target space explicitly depends on the parametrization of the base space. It is shown that this representation is valid for any gravitational field which possesses two commuting Killing vector fields. We introduce the concept of dimensional extension which allows us to consider this type of gravitational fields as strings embedded in D-dimensional nonflat backgrounds, even in the limiting case where the Killing vector fields are hypersurface orthogonal.

  Link : http://arxiv.org/abs/0809.4495

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cosmic microwave background radiation (CMB)The Big Bang theory predicts that the early universe was a very hot place and that as it expands, the gas within it cools. Thus the universe should be filled with radiation that is literally the remnant heat left over from the Big Bang, called the “cosmic microwave background radiation”, or CMB.

In 1965, two young radio astronomers, Arno Penzias and Robert Wilson, almost accidentally discovered the CMB using a small, well-calibrated horn antenna. It was soon determined that the radiation was diffuse, emanated unifromly from all directions in the sky, and had a temperature of approximately 2.7 Kelvin (ie 2.7 degrees above absolute zero). Initially, they could find no satisfactory explanation for their observations, and considered the possibility that their signal may have been due to some undetermined systematic noise.However, it soon came to their attention through Robert Dicke and Jim Peebles of Princeton that this background radiation had in fact been predicted years earlier by George Gamow as a relic of the evolution of the early Universe. This background of microwaves was in fact the cooled remnant of the primeval fireball – an echo of the Big Bang.

The CMB is nothing but a heavenly hisss…Wanna listen to it? Just click the play button.

cmb.mp3

Download

Credits:

1. Mp3- “Berlin Cosmic Microwave Experiment” (BECOME)

2. Image – Nasa

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Gravitational wave is a prediction of Einstein’s General Relativity . Gravitational waves are disturbance in curvature of space-time caused by the motions of matter and they propagate as a wave, traveling outward from a moving object or system of objects. Important examples of systems which emit gravitational waves are binary star systems, where the two stars in the binary are white dwarfs, neutron stars, or black holes.

Gravitational waves propagate through space-time at the same speed of light . It does not only propagate through space but also matter. Here is video on Gravitational wave you will like to enjoy:

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