Neutron stars, the ultra-dense cores left behind after massive stars collapse, contain the densest matter known in the Universe outside of a black hole . New results from Chandra and other X-ray telescopes have provided one of the most reliable determinations yet of the relation between the radius of a neutron star and its mass. These results constrain how nuclear matter - protons and neutrons, and their constituent quarks, interact under the extreme conditions found in neutron stars.
Neutron Stars/X-ray Binaries
It's a pleasure to welcome Martin Durant, of the University of Toronto, for a guest blog article giving more background about his work on the striking variations discovered in the Vela Pulsar.
Pulsars, the remnants of exploded massive stars, are fascinating objects. They have more mass than the sun, squeezed into a ball the size of a city, making them denser than the nucleus of an atom. Add to this mixture immense magnetic fields and rapid rotation, and you have the perfect mix of high energy particles and fundamental forces – nuclear, electromagnetic and gravitational – to put the extreme limits of physical models to the test. Each pulsar, when studied in sufficient detail, appears to be unique. To understand the differences between these exotic objects, we must use all available information and collect data across the spectrum, from radio to gamma rays.
The finite speed of light means that we must always be out of date, no matter how hard we strive to keep up with the times. The term look-back time refers to the time in the past when the light we now observe from a distant object was emitted. For example, deep Chandra observations have detected X-rays that have been travelling through intergalactic space for billions of years since they were emitted by jets of gas that were likely produced by rotating supermassive black holes. With these data, astronomers use Chandra and other telescopes as one-way time machines that enable them to see objects as they were in the past.
Observations with NASA's Chandra, Swift, and Rossi X-ray observatories, Fermi Gamma-ray Space Telescope, and ESA's XMM-Newton have revealed that a slowly rotating neutron star with a comparatively very weak surface magnetic field is giving off bursts of X-rays and gamma rays. This discovery may indicate the presence of an internal magnetic field much more intense than the surface magnetic field, with implications for how the most powerful magnets in the cosmos evolve.
The composite image on the left shows an image from NASA's Chandra X-ray Observatory in purple and an optical image from the European Southern Observatory's Very Large Telescope (VLT) in red, blue and white. The Chandra source in the center of the image is the ancient pulsar PSR J0108-1431 (J0108 for short), located only 770 light years from us. The elongated object immediately to its upper right is a background galaxy that is unrelated to the pulsar. Since J0108 is located a long way from the plane of our galaxy, many distant galaxies are visible in the larger-scale optical image.
The press and image releases from the Chandra X-ray Center cover only a small fraction of the science results produced by Chandra each year. Some results are clearly not good candidates for publicity because they're obviously incremental - I've written papers like that myself. Or they can be highly esoteric, addressing questions that only the authors knew enough about the subject to ask! It also doesn't help if the results are completely unsurprising or if there isn't a decent image.
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