A telescope mounted on the International Space Station has detected a record-breaking X-ray emanating from lightning on the remains of an exploded star.
On August 20, at 10:04 pm EDT (0204 GMT on August 21), NASA's neutron star NICER telescope (Interior Composition Explorer), located on the space station, has a sudden and extreme rise in the sky X-rays detected. According to NASA, the brightest X-ray ever observed by NICER released as much energy in 20 seconds as our sun in about 10 days.
The eruption came from the object SAX J1808.4-3658 or J1808, a pulsar (a type of neutron star or the remnants of a star that exploded as a supernova in the past). The extra bright eruption was generated by a thermonuclear flash on the surface of this pulsar. Related: This Newly Discovered X-Ray Pulsar Is Orbiting Its Partner at Record Speed
"This eruption was outstanding," said researcher Peter Bult, an astrophysicist at NASA's Goddard Space Flight Center in Maryland, said in the statement. "We are seeing a two-step brightness change, which in our opinion is caused by the ejection of separate layers from the pulsar surface, and other features that will help us decipher the physics of these powerful events."
This ultrabright record-setting event is classified as Type I X-ray Burst, the most common type. It is identified by a brightness that often rises rapidly and then slowly decreases.
With this NICER observation, scientists can improve their understanding of such extreme eruptions and learn more about what causes them on objects such as the J1808 pulsar.
Generation of a thermonuclear outbreak
Pulsars often turn quickly and emit X-rays from hotspots at their poles. J1808, which is about 11,000 light-years away from Earth in Sagittarius, rotates about 401 times per second.
The eruption on the surface of this pulsar goes back to the binary system where there is a brown dwarf (an object that is too big to be a planet and too small to be a star). Hydrogen gas flows from this object to J1808 and forms an accretion disk. After a while, this gas becomes so dense that some of its electrons lose (or ionize), which makes it harder for this gas, and thus for the light, to move around the pulsar in that disk.
Trapped in this slow motion, this energy begins to build, heat, ionize and generate even more of this "trapped energy", making it even more difficult for gas to move in the disk. Finally, the gas in the disc turns inwards until it finally falls on the pulsar. The hydrogen in the gas falls on the surface and contributes to a "sea" of such material. At the bottom of this ocean, extreme temperatures and pressures force hydrogen nuclei to merge into helium nuclei – a process known as nuclear fusion.
"The helium settles and builds its own layer, and as soon as the helium layer is a few meters deep, helium nuclei can fuse to carbon under the given conditions, causing the helium to explode and release a thermonuclear fireball over its entire surface Pulsar surface, "said Goddards Zaven Arzoumanian, the deputy chief investigator for NICER, in the statement.
After the outbreak began, the breakout's brightness diminished for a second before slowly increasing, as the NICER data showed. This short stoppage and speed change was caused by an energy build-up that blew the hydrogen layer of the pulsar into space. The helium layer of the object was next blown into space after the eruption continued to grow. After the helium layer was blown out into space, it quickly overtook the hydrogen and then sat down again on the pulsar.
After this wild explosion, the pulsar became lighter again, but scientists still can not explain this final lightening.
Researchers have studied these observations in an article published on October 23 in The Astrophysical Journal Letters.