Rotating pulsar radiates in the gamma light

Neutron star discovered in the center of the nearby supernova remnant CTA 1

The supernova remnant CTA 1 and the gamma radiation of the hidden pulsar. © NASA / S. Pineault, DRAO / G. Kanbach
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For the first time, an international team of scientists has identified a rotating neutron star - a pulsar - based on its gamma radiation. The researchers report on their discovery using the Fermi Gamma-Ray Space Telescope in the current issue of "Science Express".

The life of very massive stars ends after a few million years in a supernova. As remnants of the stars that are visible from afar, the ejected shells remain as explosion clouds and the nuclei as neutron stars or black holes. In the gas clouds, the higher elements produced by fusion reactions in the interior of the stars are distributed in the interstellar medium. After the explosion cloud has dissolved, often only the compact neutron star exists.

Lighter than the planet Venus

Ten to fifteen thousand years ago, in the constellation of Cepheus, not far from the Celestial North Pole, a magnificent new star must have shone for a few months: a supernova that beamed with the double brightness of the planet Venus. The explosion cloud of this star measures three full moon diameters in the sky today and was detected in the 1960s with a radio telescope.

This object called CTA 1 is about 4, 600 light-years from Earth, and near its center astronomers detected a compact source of X-rays and gamma rays. Presumably, this is the nucleus of the massive, exploded star - the neutron star. However, the proof of this hypothesis has not been available so far.

Pulsating light

This assumption has now been confirmed by researchers around Gottfried Kanbach from the Max Planck Institute for Extraterrestrial Physics in Garching with the new, powerful Fermi Gamma-Ray Space Telescope - formerly called GLAST - which circles the earth on a circular orbit at a height of 560 kilometers. display

With it, the rotation of a pulsar could be detected for the first time in the gamma-ray: A young, highly magnetic neutron star rotates about its axis about three times per second. An intense gamma ray, like a lighthouse, sweeps the earth - and the astronomers register a periodic (pulsating) illumination. The energy of the gamma radiation of the pulsar in CTA 1 corresponds to about one thousand times the luminosity of our sun.

Most of the 1, 800 pulsars known so far have been discovered in the radio industry and are typically one million years old. The newly discovered neutron star belongs to a small family of high-energy pulsars that has only been around ten members so far. Even more: We have a completely new type in front of us here, because without the gamma-ray measurement, this energetic, young pulsar would have remained unknown, "says Kanbach.

On the trail of the chemical evolution of the Milky Way

Young gamma pulsars such as those found in CTA 1 are therefore particularly suited to open a new window for the study of supernova remnants and our understanding of stellar evolution and the chemical evolution of the Milky Way "To deepen, " explains Kanbach. Presumably, many of the gamma sources discovered so far, but not yet identified, are members of this new class of objects, ie young pulsars.

Launched on June 11, 2008, NASA's Fermi Gamma-Ray Space Telescope has now begun scanning the entire sky with sensitivity unrivaled in the gamma range. The construction of Fermi detectors and the operation of the observatory are involved alongside NASA and the US Department of Energy Institutes in the United States, France, Italy, Sweden, Germany and Japan.

(MPG, 17.10.2008 - DLO)