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Chilling out on the youngest neutron star KEITH COOPER ASTRONOMY NOW Posted: 15 April The interior of the youngest neutron star in the Galaxy is being cooled by the emission of neutrinos, hinting at the processes that are at work inside these exotic objects, says Dr Wynn Ho of the University of Southampton, who is presenting his work today at the RAS’ National Astronomy Meeting in Glasgow.
The Cassiopeia A supernova remnant, imaged by the Chandra X-ray Observatory. Somwhere deep within the filaments of the debris is the neutron star. Image: NASA/CXC/MIT/UMass Amherst/M D Stage et al.
The neutron star in question is the Cassiopeia A supernova remnant, which is the debris of a massive star that exploded sometime in the latter part of the seventeenth century and left behind its crushed core, made almost entirely of neutron particles. Following the supernova the neutron star would have been billions of degrees hot, but has since cooled substantially to about two million degrees Celsius. Extremely hot objects emit X-rays and, for the past ten years, NASA’s Chandra X-ray Observatory has been taking snapshots of the neutron star every two years. Over this period Wynn Ho and Dr Craig Heinke of the University of Alberta in Canada observed the neutron star’s temperature drop by three percent. This temperature drop is evidence that nuclear reactions deep within the core of the neutron star are producing neutrinos that carry away thermal energy. Neutrinos are particles of barely any mass, and they very rarely interact with other matter, making their detection tricky – only ten neutrinos were detected from the far more powerful supernova 1987A. Consequently, we can only infer their presence via the cooling of the neutron star. At first the core, which is the hottest part of the neutron star, cools at a much faster rate than the outer layers because the hot conditions there produce more neutrinos. After a few hundred years the core gradually equalises in temperature with the outer layers, and the cooling becomes steady. However, although the neutron star should be around the age at which equilibrium is reached, the cooling is still observed to be a bit bumpy, implying that there are other forces at work other than neutrino emission. “The neutron star may not yet have relaxed into the steady cooling phase, or we could be seeing other processes going on,” says Dr Ho. “We don't know whether the interior of a neutron star contains more exotic particles, such as quarks, or other states of matter, such as superfluids and superconductors. We hope that with more observations, we will be able to explain what is happening in the interior in much more detail.” |
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The Planets
Hubble Reborn
3D Universe
This special publication features the photography of British astro-imager Nik Szymanek and covers a range of photographic methods from basic to advanced. Beautiful pictures of the night sky can be obtained with a simple camera and tripod before tackling more difficult projects, such as guided astrophotography through the telescope and CCD imaging.Starry Night Explore the Universe with these new versions of the award-winning Starry Night Software. Available now from the Astronomy Now Store.Exploring Mars Astronomy Now is pleased to announce the publication of Exploring Mars. The very best images of Mars taken by orbiting spacecraft and NASA's Spirit and Opportunity rovers fill up the 98 glossy pages of this special edition!Mars rover poster This new poster features some of the best pictures from NASA's amazing Mars Exploration Rovers Spirit and Opportunity. |
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