A telescope mounted to the outside of the International Space Station (ISS) picked up on a sudden spike of X-rays coming from a distant neutron star on 20 August 2019. While this kind of signal itself isn't a new discovery, the explosion was powerful enough to release, in 20 seconds, the amount of energy our sun releases in 10 days. These highly-energetic X-ray pulses are called "pulsars", which are rapidly spinning neutron stars that beam jets of charged particles from their magnetic poles.
Turns out researchers caught something extra in this particular pulsar " a signature, in the form of a huge thermonuclear flash that astronomers have dubbed 'J1808'. This pulsar, the crushed remains of a star that exploded in a supernova and is 11,400 light-years away and in the same line of sight as the constellations Sagittarius (a.k.a. the Archer) to an observer on Earth.
In the past five decades, scientists have studied these compact, mysterious stellar objects from space using different instruments that can see (and capture) different wavelengths of light, especially sensitive to astronomical phenomena like pulsars, which are far more energetic than the radio waves picked up by a variety of space/ground-based telescopes.
The Neutron star Interior Composition Explorer mission (NICER, if you'd rather) is the first mission from NASA devoted to the study of pulsars. The mission also famously observed the first recorded pulsar, known today as PSR B1919+21, in November 1967. NICER was launched to the International Space Station in June 2017 and began its science experiments in July the same year.
X-ray observations made by NICER are a window into some of the lesser-known fundamental forces in the natural universe that may or may not challenge the laws of physics as we understand it. The inner working of a pulsar simply don't exist anywhere else and can't be reproduced in a laboratory as of today, which makes them interesting subjects for astrophysics researchers.
"What's inside a pulsar?" is one of many long-standing astrophysics questions about these ultra-dense, fast-spinning, powerfully magnetic objects, according to a NASA press release.
Today, scientists know of over 2,000 pulsars. These rotating "lighthouse" neutron stars begin their lives as stars between about seven and 20 times the mass of our sun. Some are found to spin hundreds of times per second, faster than the blades of a household blender, and they possess enormously strong magnetic fields.
The newly-observed rarity offered some interesting insight about pulsars " there was a brief expansion of its many layers as the intensity was built up and the energy of the blast built up enough to blow the pulsar's hydrogen layer into space. The flickering of these "burst oscillations" is also interesting to scientists since it appears to rise and fall at the pulsar's spinning frequency, just like its X-ray signals do. Yet, these happen at different locations on the pulsar's surface than the hotspots associated with its normal X-ray pulses.
A paper describing the findings has been published by The Astrophysical Journal Letters.