Archive for the ‘Pulsars’ Category

Former Missile-Tracking Telescope Helps Reveal Fate Of Baby Pulsar

November 5, 2013 Leave a comment

A radio telescope once used to track ballistic missiles has helped astronomers determine how the magnetic field structure and rotation of the young and rapidly rotating Crab pulsar evolves with time. The findings are published in the journal Science today (Friday).

The Crab pulsar is a neutron star which formed in a massive cosmic explosion seen in both Europe and China in AD 1054 as a bright star in the daytime sky. Now rotating 30 times a second, this highly-compact star emits beams of radio waves that, like a lighthouse, produce flashes each time it rotates. The star itself is only about 25 km across but contains the mass of nearly 1 million Earths.

Professor Andrew Lyne and his colleagues from The University of Manchester report on a steady change in these flashes during a 22-year experiment watching the star, telling us about its very strong magnetic field and helping us learn about the otherwise-inaccessible interior of the star.

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Astronomers Uncover A ‘Transformer’ Pulsar

October 1, 2013 Leave a comment

An international team of scientists using a fleet of orbiting X-ray telescopes, including NASA’s Swift and Chandra X-ray Observatory, has discovered a millisecond pulsar with a dual identity. In a feat that has never before been observed, the star readily shifts back and forth between two mutually exclusive styles of pulsed emission — one in X-rays, the other in radio.

The discovery, say scientists, represents a long-sought intermediate phase in the life of these powerful objects.

“This transitional object took us decades to find, and it provides us with a unique opportunity to observe a pulsar’s intense magnetic field in action,” said Sergio Campana, an astronomer at Brera Observatory in Merate, Italy, and a co-author of a paper on the object that appears in the Sept. 26 issue of the journal Nature.

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Astronomers Use Precision Pulsar Positions To Break Record

An international team of scientists led by astronomer Adam Deller (ASTRON) have used the Very Long Baseline Array (VLBA) to set a new distance accuracy record, pegging a pulsar called PSR J2222-0137 at 871.4 light-years from Earth. They did this by observing the object over a two-year period to detect its parallax, the slight shift in apparent position against background objects when viewed from opposite ends of Earth’s orbit around the Sun. With an uncertainty less than four light-years, this distance measurement is 30 percent more accurate than that of the previous-best pulsar distance. The VLBA observations were even able to discern the orbital motion of the pulsar around its as-yet undetected companion object, despite this motion being no larger than a small coin observed at a tenth of the distance to the Moon. The results of the research have been published in The Astrophysical Journal.

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Baffling Pulsar Leaves Astronomers In The Dark

February 6, 2013 Leave a comment

New observations of a highly variable pulsar using ESA’s XMM-Newton are perplexing astronomers. Monitoring this pulsar simultaneously in X-rays and radio waves, astronomers have revealed that this source, whose radio emission is known to ‘switch on and off’ periodically, exhibits the same behaviour, but in reverse, when observed at X-ray wavelengths. It is the first time that a switching X-ray emission has been detected from a pulsar, and the properties of this emission are unexpectedly puzzling. As no current model is able to explain this switching behaviour, which occurs within only a few seconds, these observations have reopened the debate about the physical mechanisms powering the emission from pulsars.

“There is a general agreement about the origin of the radio emission from pulsars: it is caused by highly energetic electrons, positrons and ions moving along the field lines of the pulsar’s magnetic field, and we see it pulsate because the rotation and magnetic axes are misaligned,” explains Wim Hermsen from SRON, the Netherlands Institute for Space Research in Utrecht, The Netherlands. “How exactly the particles are stripped off the neutron star’s surface and accelerated to such high energy, however, is still largely unclear,” he adds.

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A Black Widow’s Tango Mortale In Gamma-Ray Light

October 26, 2012 Leave a comment

Pulsars are the compact remnants from explosions of massive stars. Some of them spin around their own axis hundreds of times per second, emitting beams of radiation into space. Until now, they could only be found through their pulsed radio emissions. Now, scientists at the Max Planck Institute for Gravitational Physics (Albert Einstein Institute/AEI) in Hanover assisted by the Max Planck Institute for Radio Astronomy have discovered a millisecond pulsar solely via its pulsed gamma radiation. A new data analysis method developed by the AEI was crucial for the success. The pulsar is accompanied by an unusual sub-stellar partner, which it is vaporizing, hence the name “black widow”.

To unambiguously identify a gamma-ray pulsar, astronomers must know its properties to very high precision. This includes its position, spin frequency, and how the latter changes over time. If the pulsar is in a binary system, the analysis problem is even more complicated: at least three additional orbital parameters have to be determined as well.

“We developed a particularly efficient method to search the data from NASA’s Fermi satellite for gamma-ray millisecond pulsars, including those in binary systems. Only this method enabled us to probe the wide parameter ranges,” says Holger Pletsch, lead author of the article published in Science. The new analysis method enables scientists to conduct a ‘blind search’ for gamma-ray millisecond pulsars for the first time – right up to very high spinning frequencies.

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Has The Speediest Pulsar Been Found?

NASA’s Chandra X-ray Observatory and ESA’s XMM-Newton in space, and the Parkes radio telescope in Australia — may have found the fastest moving pulsar ever seen.

The large area of diffuse X-rays seen by XMM-Newton was produced when a massive star exploded as a supernova, leaving behind a debris field, or supernova remnant known as SNR MSH 11-16A. Shocks waves from the supernova have heated surrounding gas to several million degrees Kelvin, causing the remnant to glow brightly in X-rays.

The Chandra image reveals a comet-shaped X-ray source well outside the boundary of the supernova remnant. This source consists of a point-like object with a long tail trailing behind it for about 3 light years.

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Interstellar Beacons Could Help Future Astronauts Find Their Way

The use of stars, planets and stellar constellations for navigation was of fundamental importance for mankind for thousands of years. Now a group of scientists at the Max-Planck Institute for Extraterrestrial Physics in Garching, Germany have developed a new technique using a special population of stars to navigate not on Earth, but in voyages across the universe. Team member Prof. Werner Becker will present their work at the National Astronomy Meeting in Manchester on Friday 30 March.

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