NICER Caught a Astronomical Event That Caused a Thermonuclear Blast

NICER, or the Neutron star Interior Composition ExploreR is a NASA endeavor that studies the electromagnetic, gravitational, and nuclear-physics aspects of neutron stars. Examining the state of matter within these celestial objects, NICER is able to bring scientists to understand the reactions and behavior of these parts of our universe, that until now we were unable to observe, at least in this way.

But a recent discovery this year has made scientists really excited. The NICER detected a huge thermonuclear flash emanating from a pulsar, or the remnants of a collapsed star. This was the brightest event ever observed by NASA, and came from an object in space called J1808. A number of phenomenon occurred during the observation, including the brightness flashing again after it dimmed, something scientists still are unable to explain.

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Via NICER Catches Milestone X-ray Burst | NASA Goddard
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SAX J1808, or J1808 is a binary system that is approximately 11 million light years away from Earth. Here, you can see the pulsar, or collapsed star, surrounded by a ring of hydrogen gas and others. It is larger than a planet, but smaller than a star.
Every few years, the disc becomes unstable, causing a massive release of gas into the gravitational pull of the pulsar.

Via NICER Catches Milestone X-ray Burst | NASA Goddard
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These escaped gasses begin to be absorbed into the pulsar all at once. The pulsar, with enormous gravitational forces, sucks in the errant gasses onto its surface. There they gather and create an additional layer over the present one, until there is simply too much energy stored there.

Via NICER Catches Milestone X-ray Burst | NASA Goddard
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Hydrogen molecules fall to the surface, where they mix with and fuse with a layer of helium already on the surface. Similar to the reactions occurring on the surface of our Sun, once these gasses reach high enough concentrations, a powerful thermonuclear reaction occurs as the energy and gasses are expelled outward. This is also called a Type I X-Ray Burst.

Via NICER Catches Milestone X-ray Burst | NASA Goddard
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The brief but intense explosion first blows off the hydrogen layer, which expands before eventually dissipating. The increasing radiation eventually reaches a point where it blows off the helium layer as well.

Via NICER Catches Milestone X-ray Burst | NASA Goddard
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The remaining gasses after this secondary explosion begin to cool, eventually being reabsorbed by the pulsar. Though it took only 20 seconds, the amount of energy released was the same that the Sun gives off in 10 days.

Via NICER Catches Milestone X-ray Burst | NASA Goddard