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NASA's NICER telescope on ISS captures X-burst recording setting



NASA has detected a massive thermonuclear explosion coming from outer space, caused by a massive thermonuclear flash on the surface of a pulsar – the crushed remains of a star that long ago exploded like a supernova.

The explosion released as much energy in 20 seconds as the sun does in almost ten days.

NASA's Neutron Star Interior Composition Explorer (NICER) telescope at the International Space Station (ISS) discovered a sudden spike of X-rays on August 20, the United States Space Agency reports.

The X-ray burst, the brightest that NICER has seen so far, came from an object named "J1808".

The observations reveal many phenomena that have never been seen together in a single burst. [1

9659002] In addition, the sinking fireball briefly shone again for reasons that astronomers cannot yet explain.

"This burst was outstanding. We see a two-step change in brightness, which we believe is caused by the ejection of separate layers from the pulse surfac e, and other features that help us decode the physics of these powerful events," says the lead researcher Peter Bult, an astrophysicist at NASA's Goddard Space Flight Center in Maryland.

The detail NICER captured in this record burst will help astronomers fine-tune their understanding of the physical processes driving the thermonuclear inflations of it and other explosive pulsars.

"J1808" lies about 11,000 light-years away in the constellation Sagittarius.

It spins in a staggering 401 rotations every second, and is a member of a binary system. Its companion is a brown dwarf, an object larger than a giant planet but still too small to be a star. A steady stream of hydrogen flows from the companion to the neutron star, and it accumulates in a huge storage structure called an accretion disk.

Astronomers use a concept called the "Eddington Frontier", named after the English astrophysicist Sir Arthur Eddington, to describe the maximum radiation intensity a star can have before that radiation causes the star to expand.

This point is strongly dependent on the composition of the material above the emission source.

"Our study utilizes this long-standing concept in a new way," said co-author Deepto Chakrabarty, professor of physics at MIT.

"We apparently see the Eddington boundary for two different compositions in the same X-ray. This is a very powerful and direct way of following the nuclear reactions that underlie the incident."

A document describing the results has been published by The Astrophysical Journal Letters.


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