Mystery Neutron Star Discovered

Last week we posted a fascinating piece on Neutron Stars and the Physics of Star Trek, which began by describing an episode from Star Trek, "Evolution," when the Nanites began eating the ship's computers as the crew was studying a neutron star that was about to erupt into the most spectacular explosion in the known universe -a supernova.

Astronomer's at the Harvard Chandra X-Ray Telescope took a new image that shows the 2,000 year-old-remnant of such a cosmic explosion, known as RCW 103, which occurred about 10,000 light years from Earth.

In Chandra's image (above), the colors of red, green, and blue are mapped to low, medium, and high-energy X-rays. At the center, the bright blue dot is likely the neutron star that astronomers believe formed when the star exploded. For several years astronomers have struggled to understand the behavior of the this object, which exhibits unusually large variations in its X-ray emission over a period of years.

Neutron stars are extremely dense remnants of exploded stars about the size of Manhattan consisting of tightly packed neutrons. When stars are more massive than about 8 times the Sun, they end their lives in a spectacular explosion called a supernova. The outer layers of the star are hurtled out into space at thousands of miles an hour, leaving a debris field of gas and dust. Where the star once was located, a small, collapsed, incredibly dense object, a neutron star, is often found. While only 10 miles or so across, the tightly packed neutrons in such a star contain more mass than the entire Sun.

The result of the final implosion is an unimaginably compacted core: atoms would be crushed together with their electrons squeezed into the nucleus, forming neutrons and a neutron star, with a core so dense that a single spoonful would weigh 200 billion pounds.

Most neutron stars house incredibly large magnetic fields. If they are spinning rapidly they make fabulous clocks, cosmic radio beacons we call pulsars. Pulsars can keep time to an accuracy better that one microsecond per year. Some pulsars generate more than 1000 pulses per second, which means, as Lawrence Krauss wrote in The Physics of Star Trek, that an object with the mass of the Sun packed into an object 10 to 20 kilometers across is rotating over 1000 times per second, or more that half the speed of light!

Oddly, though new evidence from Chandra implies that the neutron star near the center of RCW 103 is rotating only once every 6.7 hours, confirming recent work from the XMM-Newton Space Telescope. This is much slower than a neutron star of its age should be spinning.

One possible solution to this mystery is that the massive progenitor star to RCW 103 may not have exploded in isolation. Rather, a low-mass star that is too dim to see directly may be orbiting around the neutron star. Gas flowing from this unseen neighbor onto the neutron star might be powering its X-ray emission, and the interaction of the magnetic field of the two stars could have caused the neutron star to slow its rotation.

Posted by Casey Kazan

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