Albert Einstein's theory on general relativity holds that the moment that marked the beginning of the Universe also determined the conception of gravitational waves. These are fluctuations that develop in the curvature of space and time, but, until now, they have proven to be extremely difficult to detect. One possible way of breaking this deadlock, experts say, is to analyze the light coming in from fast, millisecond pulsars, which spin several hundred times per second.
When some massive stars collapse and explode into a supernova, their cores compact the mass of the Sun into the size of the city. The conserved angular momentum within forces the whole star, now made entirely out of neutrons, to spin faster than a kitchen blender. Some of these neutron stars can spin several hundred times per second, emitting a beam of gamma-ray radiation that is visible from the Earth if it slams us head-on. When such a space structure is aligned correctly, we can see its light sweeping over us periodically, causing pulsations. This is the main reason why these stars are called pulsars.
An important thing to know about these pulsars is that they are extremely precise. In other words, their sweeps occur at clearly defined, periodic intervals, and some astronomers even go as far as saying that the stars are the most accurate natural clocks of the Universe. What investigators are hoping to accomplish at this point is the creation of a Global Positioning System (GPS) of sorts that will use the periodic sweeps of several pulsars in order to look for gravitational waves. At the forefront of this research, however, is NASA's Fermi Gamma-ray Space Telescope, which is able to detect the highly energetic photons making up this type of electromagnetic radiation.
Discovering millisecond pulsars is tremendously difficult, and only some 60 were discovered in the Milky Way since experts started looking for them. Therefore, Fermi acts like a pointer. It scans the skies non-stop, looking for gamma-ray sources, and then alerts its control team to the discoveries. Other telescopes are then used to determine the accuracy of the original findings, and the new objects are added to the international database that contains all known pulsars. And many of them are needed for the GPS system, experts say.
As they travel through the Universe, gravitational waves should produce gravitational radiation, which should become visible as nothing more than a wiggle inside the GPS “natural clock” network. If such abnormalities were discovered in the radiation “lightbeams” that the pulsars generated, then this could constitute definitive proof that gravitational waves did exist, experts said yesterday in Washington DC, at the 215th meeting of the American Astronomical Society (AAS).
“The Global Positioning System uses time-delay measurements among satellite clocks to determine where you are on Earth. Similarly, by monitoring timing changes in a constellation of suitable millisecond pulsars spread all over the sky, we may be able to detect the cumulative background of passing gravitational waves,” National Radio Astronomy Observatory (NRAO) researcher Scott Ransom said, quoted by
Space.
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