XMM-Newton and Suzaku help pioneer method for probing exotic matterAugust 28, 2007Astronomers using XMM-Newton and Suzaku have seen Einstein's predicted distortion of space-time and pioneered a ground-breaking technique for determining the properties of neutron stars. ESA's XMM-Newton and the JAXA/NASA Suzaku X-ray observatories have been used to see the distortion of space-time around three neutron stars. These objects contain the densest observable matter in the Universe. Neutron stars cram more than a Sun's worth of material into a city-sized sphere. This means that a cup of neutron-star stuff would outweigh Mount Everest. Astronomers use these collapsed stars as natural laboratories to study how tightly matter can be compacted under the most extreme pressure that nature can offer. "This is fundamental physics," says Sudip Bhattacharyya at NASA's Goddard Space Flight Center, USA. "There could be exotic kinds of particles or states of matter, such as quark matter, in the centres of neutron stars, but it's impossible to create them in the lab. The only way to find out is to understand neutron stars."
To address this mystery, scientists must accurately and precisely measure the diameters and masses of neutron stars. In two concurrent studies, one with XMM-Newton and the other with Suzaku, astronomers have taken a big step forward. Using XMM-Newton, Bhattacharyya and his colleague Tod Strohmayer observed a binary system known as Serpens X-1, which contains a neutron star and a stellar companion. They studied a spectral line from hot iron atoms that are whirling around in a disc, just beyond the neutron star's surface, at 40% the speed of light. Previous X-ray observatories detected iron lines around neutron stars, but they lacked the sensitivity to measure the shapes of the lines in detail. Thanks to XMM-Newton's large mirrors, Bhattacharyya and Strohmayer found that the iron line is broadened asymmetrically by the gas's extreme velocity, which smears and distorts the line because of the Doppler effect and beaming effects predicted by Einstein's special theory of relativity. The warping of space-time by the neutron star's powerful gravity, an effect of Einstein's general theory of relativity, shifts the neutron star's iron line to longer wavelengths. "We have seen these asymmetric lines from many black holes, but this is the first confirmation that neutron stars can produce them as well. It shows that the way neutron stars accrete matter is not very different from that of black holes, and gives us a new tool to probe Einstein's theory," says Strohmayer. A group led by Edward Cackett and Jon Miller of the University of Michigan, which includes Bhattacharyya and Strohmayer, used Suzaku's superb spectral capabilities to survey three neutron-star binaries: Serpens X-1, GX 349+2, and 4U 1820-30. This team observed a nearly identical iron line in Serpens X-1, confirming the XMM-Newton result. It detected similarly skewed iron lines in the other two systems as well. "We're seeing the gas whipping around just outside the neutron star's surface," says Cackett. "And since the inner part of the disc obviously cannot orbit any closer than the neutron star's surface, these measurements give us a maximum size of the neutron star's diameter. The neutron stars can be no larger than 29 to 33 km across, results that agree with other types of measurements." "Now that we have seen this relativistic iron line around three neutron stars, we have established a new technique," adds Miller. "It's very difficult to measure the mass and diameter of a neutron star, so we need several techniques to work together to achieve that goal." Knowing a neutron star's size and mass allows physicists to describe the 'stiffness' (or equation of state) of matter packed inside these incredibly dense objects. Besides using these iron lines to test Einstein's general theory of relativity, astronomers can use them to probe conditions in the inner part of a neutron star's accretion disc. European Space Agency Science News and Science Current Events Tag Cloud This tag cloud is a visual representation of term frequencies of random science news topics with common terms grouped together and emphasized by their display size. Gamma Ray Down syndrome Radiation Treatment Cancer Treatment Butterflies Brain Tumors Schizophrenia Dinosaur Spinal Cord Injury Blood transfusion Second-hand Smoke Curcumin Cox-2 Inhibitors Autophagy Electrons Fisheries Brain Region Narcolepsy Drug Discovery Liver Injury Glaucoma Quantum Physics Vitamin D Vitamin C Polyphenols
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Related Neutron Star Current Events and Neutron Star News Articles Keck Study Sheds New Light on 'Dark' Gamma-ray Bursts Gamma-ray bursts are the universe's biggest explosions, capable of producing so much light that ground-based telescopes easily detect it billions of light-years away. Rare radio supernova in nearby galaxy is nearest supernova in five years The chance discovery last month of a rare radio supernova - an exploding star seen only at radio wavelengths and undetected by optical or X-ray telescopes - underscores the promise of new, more sensitive radio surveys to find supernovas hidden by gas and dust. Astronomers catch a star being revved-up Researchers have witnessed a star being transformed into an object that spins at almost 600 times a second using telescopes in the USA and the Netherlands, and CSIRO's Parkes telescope in Australia. Star crust 10 billion times stronger than steel, IU physicist finds Research by a theoretical physicist at Indiana University shows that the crusts of neutron stars are 10 billion times stronger than steel or any other of the earth's strongest metal alloys. A young pulsar shows its hand A small, dense object only twelve miles in diameter is responsible for this beautiful X-ray nebula that spans 150 light years. NASA's Fermi Telescope Reveals Best-Ever View of Gamma-Ray Sky A new map combining nearly three months of data from NASA's Fermi Gamma-ray Space Telescope is giving astronomers an unprecedented look at the high-energy cosmos. To Fermi's eyes, the universe is ablaze with gamma rays from sources ranging from within the solar system to galaxies billions of light-years away. NASA's Swift, Fermi Probe Fireworks From a Flaring Gamma-Ray Star Astronomers using NASA's Swift satellite and Fermi Gamma-ray Space Telescope are seeing frequent blasts from a stellar remnant 30,000 light-years away. Scientists Discover New Planet Orbiting Dangerously Close to Giant Star A team of astronomers from Penn State and Nicolaus Copernicus University in Poland has discovered a new planet that is closely orbiting a red-giant star, HD 102272, which is much older than our own Sun. First gamma-ray-only pulsar observation opens new window on stellar evolution About three times a second, a 10,000-year-old stellar corpse sweeps a beam of gamma-rays toward Earth. NASA'S Fermi Telescope Discovers First Gamma-Ray-Only Pulsar About three times a second, a 10,000-year-old stellar corpse sweeps a beam of gamma-rays toward Earth. Discovered by NASA's Fermi Gamma-ray Space Telescope, the object, called a pulsar, is the first one known that only "blinks" in gamma rays. More Neutron Star Current Events and Neutron Star News Articles |
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