NASA has released an image of a short spike of X-rays bursting out from a pulsar. While it captures a fascinating moment in space science, the dramatic colors almost make it seem like the world-ending finale to a high-octane anime.
The agency explained Thursday that Neutron Star Interior Composition Explorer, or NICER for short, spotted the sudden surge on August 20 at 10:04 p.m. Eastern time. The rays emanated from the surface of a pulsar, the crushed leftovers from a star that exploded in a supernova. The thermonuclear flash witnessed in the image captured a number of firsts, including an unexplained phenomenon where the rays suddenly brightened toward the end. The team has written about the event in The Astrophysical Journal Letters.
“This burst was outstanding,” lead researcher Peter Bult, an astrophysicist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, and the University of Maryland, College Park, said in a statement. “We see a two-step change in brightness, which we think is caused by the ejection of separate layers from the pulsar surface, and other features that will help us decode the physics of these powerful events.”
Scientists classify the X-ray burst as a Type I, which refers to bursts with a quick rise and slow decline. The burst in question released around the same amount of energy in 20 seconds as the Sun does in 10 days.
A pulsar is an object characterized by its rapid spinning, which sends out X-rays from its magnetic poles. This pulsar is known as SAX J1808.4-3658, or J1808, and it’s located around 11,000 light-years away in the constellation Sagittarius. A nearby brown dwarf supplies hydrogen gas that gets trapped into an accretion disk. The disk becomes dense enough that its atoms start to lose its electrons, with hydrogen falling onto the pulsar and fusing into helium as it rains down.
“The helium settles out and builds up a layer of its own,” Zaven Arzoumanian, the deputy principal investigator for NICER and a co-author of the paper, said in a statement. “Once the helium layer is a few meters deep, the conditions allow helium nuclei to fuse into carbon. Then the helium erupts explosively and unleashes a thermonuclear fireball across the entire pulsar surface.”
NICER: how it’s capturing more of space than ever before
The NICER that captured the burst is a spectrometer fitted with 56 telescopes. It’s designed to spot emissions from neutron stars from far away, both thermal and non-thermal. While neutron stars come in with pulsar and magnetar forms, NICER is primarily focused on the pulsars that send out beams from their magnetized core. The system is also designed to test using pulsars as navigation beacons.
The instrument launched to the International Space Station on a SpaceX Falcon 9 in June 2017 as part of Commercial Resupply Service mission 11, or CRS-11.
It’s not the first impressive image captured during NICER’s time at the space station. In January 2019, it captured the “light echoes” around a new black hole 10 times the mass of the sun:
In May 2019, it captured X-ray patterns across the night sky:
With NASA’s new instrument, space is now looking a whole lot NICER.
Read the abstract of the team’s most recent paper below:
The Neutron Star Interior Composition Explorer (NICER) has extensively monitored the 2019 August outburst of the 401 Hz millisecond X-ray pulsar SAX J1808.4–3658. In this Letter, we report on the detection of a bright helium-fueled Type I X-ray burst. With a bolometric peak flux of (2.3 ± 0.1) × 10−7 erg s−1 cm−2, this was the brightest X-ray burst among all bursting sources observed with NICER to date. The burst shows a remarkable two-stage evolution in flux, emission lines at 1.0 and 6.7 keV, and burst oscillations at the known pulsar spin frequency, with ≈4% fractional sinusoidal amplitude. We interpret the burst flux evolution as the detection of the local Eddington limits associated with the hydrogen and helium layers of the neutron star envelope. The emission lines are likely associated with Fe, due to reprocessing of the burst emission in the accretion disk.