суббота, 9 ноября 2019 г.

NASA's NICER Catches Record-setting X-ray Burst

ISS - NICER - SEXTANT Mission patch.

Nov. 8, 2019

NASA’s Neutron star Interior Composition Explorer (NICER) telescope on the International Space Station detected a sudden spike of X-rays at about 10:04 p.m. EDT on Aug. 20. The burst was caused by a massive thermonuclear flash on the surface of a pulsar, the crushed remains of a star that long ago exploded as a supernova.

Image above: Illustration depicting a Type I X-ray burst. The explosion first blows off the hydrogen layer, which expands and ultimately dissipates. Then rising radiation builds to the point where it blows off the helium layer, which overtakes the expanding hydrogen. Some of the X-rays emitted in the blast scatter off of the accretion disk. The fireball then quickly cools, and the helium settles back onto the surface. Image Credits: NASA's Goddard Space Flight Center/Chris Smith (USRA).

The X-ray burst, the brightest seen by NICER so far, came from an object named SAX J1808.4-3658, or J1808 for short. The observations reveal many phenomena that have never been seen together in a single burst. In addition, the subsiding fireball briefly brightened again for reasons astronomers cannot yet explain.

“This burst was outstanding,” said lead researcher Peter Bult, an astrophysicist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, and the University of Maryland, College Park. “We see a two-step change in brightness, which we think is caused by the ejection of separate layers from the pulsar surface, and other features that will help us decode the physics of these powerful events.”

The explosion, which astronomers classify as a Type I X-ray burst, released as much energy in 20 seconds as the Sun does in nearly 10 days. The detail NICER captured on this record-setting eruption will help astronomers fine-tune their understanding of the physical processes driving the thermonuclear flare-ups of it and other bursting pulsars.

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