on august 21′ st, 2019, NASA’s NICER telescope on the ISS, observed the largest x-ray burst to date. the flare-up came from SAX j1808.4-3658, a binary system 11,000 light-years away, where a brown dwarf, a failed star to big to be a planet but not big enough to become a star, is orbiting a pulsar. the pulsar draws gas from its companion, the brown dwarf. hydrogen forms a disc around the pulsar. every few years, the disc becomes unstable. the strong magnetic field pulls the gas in, and fuses the hydrogen into helium, kind of like what is happening with our star!
then, when the conditions are just right. the helium layer expands with a brief, thermonuclear fireball. this is called a type-1a x-ray burst. some x-rays that are emitted bounce of the accretion disc. then, the helium settles back onto the surface. all this happens in 20 seconds!
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