Japan’s XRISM Astronomical Satellite on a Mission To Investigate the X-Ray Rainbow of the Universe Using Resolve Detector

Astronomers will glimpse the universe in X-ray light with an extraordinary combination of light-gathering power and energy resolution. The X-Ray Imaging and Spectroscopy Mission (XRISM), an astronomical satellite of the Japan Aerospace Exploration Agency (JAXA), will demonstrate this capability to distinguish rays of different energies.

A Glimpse of the Hot Universe

XRISM is scheduled to be lifted off by JAXA from Japan's Tanegashima Space Center on August 26, 2023, using an H-II rocket as its launching vehicle. It serves as the seventh Japanese X-ray observatory following the ASTRO-H Hitomi declared lost on April 28 after losing contact with spacecraft controllers.

XRISM aims to recover the promises of Hitomi's mission, focusing on resolving astrophysical problems through precise X-ray spectroscopy. It is designed to address some questions about the cosmos, such as the structure formation of the universe and the evolution of galaxy clusters. It also aims to investigate the circulation history of baryonic matter and the transport and circulation of energy in the universe.

Another one of the objectives of the mission is conducting high-resolution X-ray spectral observations of the hot gas plasma wind which blows through the galaxies in the universe. This will be made possible using a Resolve detector.

How Will the Resolve Detector Work?

Resolve is an X-ray microcalorimeter spectrometer tool developed in collaboration between NASA and JAXA. It measures the small temperature changes created when an X-ray strikes its 6-by-6-pixel detector. Then the sensor measures the tiny temperature increase and identifies the X-ray's energy by cooling it to negative 460 degrees Fahrenheit. After that, the instrument will reach its operating temperature after undergoing a multistage mechanical cooling process inside a liquid helium container as small as a refrigerator. Upon collecting thousands or millions of X-rays from a celestial object, Resolve will measure its high-resolution spectra.

Spectra refers to the measurement of the intensity of light over various ranges of energies. Most people are familiar with the colors of the rainbow as the components of visible light are spread by prisms. In early versions of spectrometers, scientists used prisms when searching for spectral lines, which appear when atoms or molecules absorb or release energy.

Recently, astronomers made innovations by using spectrometers tuned to all kinds of light to investigate cosmic objects' motions, physical states, and compositions. For Resolve, it will perform spectroscopic measurements for X-rays with energies that range from 400 to 12,000 electron volts. The energies of individual X-rays will be measured to form a spectrum.

According to XRISM principal investigator Richard Kelley from NASA's Goddard Space Flight Center, Resolve can provide new insights into some of the most energetic objects in the universe, such as black holes, galaxy clusters, and remnants of stellar explosions. He is also confident that astronomers will learn more about the behavior of these celestial objects and their composition once the mission sends data collected after the launch.