NASA builds a map of all the sky seen by X-rays, line by line with its NICER experience

In June 2017, NASA's Neutron Star Interior Composition Explorer was installed aboard the International Space Station (ISS). The purpose of this instrument is to provide high-precision measurements of neutron stars and other super-dense objects that are about to collapse into black holes. NICER is also the first instrument designed to test the technology that will use pulsars as navigation beacons.

NASA recently used data obtained during the first 22 months of NICER's scientific operation to create an X-ray map of the entire sky. This resulted in a beautiful image that resembles a long exposure image of fire dancers, to a solar flare activity caused by hundreds of stars or even to a web viewing. But in reality, each luminous point represents a source of X-rays, while the luminous filaments constitute their path in the night sky.

NICER's main scientific goal is to target and track the cosmic sources of X-rays and other energetic particles as the ISS rotates around the Earth every 93 minutes. However, the instrument detectors remain active even when it is "night" aboard the station, during which time they will walk between the targets.

It is these data, collected during the "night movements" of the NICER instrument, that contributed to the creation of the image. Each arc follows the movements of particularly bright X-ray sources – composed of pulsars, black holes and distant galaxies (shown in the picture above) – with respect to the ISS that revolves around the Earth.

The brightness of each point is the result of the time spent by the NICER instrument to observe it directly, as well as any additional energy captured during its "night movements". The image also reveals a diffuse glow that penetrates the sky even far from the light sources, which corresponds to the X-ray background (XRB).

The major arcs, on the other hand, are due to the fact that NICER often follows the same paths between targets, the brightest being sources that NICER regularly monitors. Keith Gendreau, lead investigator at NASA's Goddard Space Flight Center, summarized the importance of NICER in a recent NASA press release:

"Even with minimal processing, this image reveals the Cygnus Loop, a supernova remnant of about 90 light-years in diameter and believed to be 5,000 to 8,000 years old. We are gradually building a new X-ray image of all the sky, and it is possible that NICER's nocturnal scans reveal previously unknown sources. "

The main mission of NICER is to determine the size and density of stellar remains such as neutron stars with a margin of error of 5%. Pulsars, which are rapidly rotating neutron stars that appear impulsive (hence its name), are among NICER's usual targets because they are perfectly suited to this type of "mass-ray" search.

These measures that NICER brings together will help physicists finally solve the mystery of the form that matter takes in the nuclei of these super-compressed objects. In addition to NICER, pulsars are the main research center of the SEXTANT (Station Explorer) experiment for X-ray synchronization and navigation technology, which could contribute to the development of state-of-the-art navigation technology for space.

Like a GPS system, SEXTANT uses precise synchronization of pulsar X-ray pulses to autonomously determine the position and speed of NICER in space. Combined with NICER's proven ability to use pulsars as a timing source, this technology could be used to develop a deep space navigation system that can be used to conduct missions throughout the solar system, or even interstellar space.

Further reading: NASA