In September 2023, the joint Japan Aerospace Exploration Agency (JAXA), European Space Agency (ESA), and NASA X-Ray Imaging and Spectroscopy Mission (XRISM) telescope launched into low-Earth orbit atop a Japanese H-IIA rocket. Since then, the X-ray telescope has undergone a commissioning phase and officially begun performing scientific observations on the universe’s structure, outflows from galaxy nuclei, dark matter, and more.
One of XRISM’s first targets were black holes and supernova remnants. During these observations, the telescope collected data on the environments surrounding these objects, which allowed scientists to investigate the structure, motion, and temperature of the material surrounding these objects. The team of scientists recently presented their results, which are also the first scientific results from XRISM to be published, to the public.
As mentioned, XRISM is an X-ray telescope that is capable of observing the highly energetic X-ray light that is produced by the extremely hot gas within and around supernova remnants and black holes. With its advanced X-ray technology and instruments, XRISM is able to reveal the speed and temperature of the material and gas around these objects, as well as the three-dimensional structures that are produced around black holes, exploded stars, and other cosmic objects.
“These new observations provide crucial information in understanding how black holes grow by capturing surrounding matter and offer a new insight into the life and death of massive stars. They showcase the mission’s exceptional capability in exploring the high-energy Universe,” said Matteo Guainazzi, who serves as an XRISM project scientist for the European Space Agency (ESA).
Infographic detailing XRISM, its instruments, and goals. (Credit: ESA)
In the newly published results, the scientists focused on supernova remnant N132D and a supermassive black hole located within the galaxy NGC 4151. N132D was a part of XRISM’s “first light” observations and is located within the Large Magellanic Cloud, approximately 160,000 light-years from Earth, and is believed to have been created from the explosion of a massive star around 3,000 years ago.
XRISM was able to reveal the structure surrounding N132D through the use of its Resolve instrument, which is an X-ray spectrometer that operates as a microcalorimeter that detects X-ray photons as they hit a detector. When the photons are detected, the detector warms up, changing the detector’s conductive properties and allowing for the energy of the absorbed X-ray photons to be calculated.
Before XRISM’s observations of N132D, scientists believed the remnant was spherically shaped, but were surprised to find that the remnant is actually shaped like that of a doughnut. The scientists were able to measure the velocity of the gas and material surrounding the remnant through the use of the Doppler effect. Their results showed that the remnant is expanding at a speed of around 1,200 km per second.
Image showing XRISM’s observation of supernova remnant N132D and the energy levels of different materials within the remnant. (Credit: JAXA)
Resolve also utilized its spectrometer characteristics to reveal the elements and compounds present within the remnant. The instrument found traces of iron that could be as hot as 10 billion degrees Kelvin. The iron atoms were heated to these extraordinary temperatures through violet shock waves produced during the supernova explosion that ultimately resulted in the remnant. Astronomers have long predicted this phenomenon, but it had never been directly observed until XRISM’s observations.
N132D is an example of a supernova remnant that could hold important clues and insight into how stars evolve over time and how elements, especially elements vital to the existence of life, are distributed throughout the universe. XRISM is one of the first X-ray observatories to directly reveal the velocity and temperature distribution of gas and material surrounding a supernova remnant, as previous X-ray observatories have had difficulty revealing such characteristics.
In addition to N132D, XRISM also investigated the environment surrounding a black hole within the spiral galaxy NGC 4151, which is located around 62 million light-years from Earth. XRISM’s new observations revealed the presence of a mysterious structure of gas and material surrounding the black hole, which masses at around 30 times that of the Sun.
Using Resolve and other instruments, XRISM observed the matter circling and ultimately falling into the black hole. The radius at which this matter circles spans from 0.001 to 0.1 light-years, which is comparable to the distance between the Sun and Uranus multiplied by 100.
Scientists were able to map out the three-dimensional structures surrounding the black hole by determining the X-ray signatures produced by the motions of iron atoms. Their results showed three distinct regions of matter and gas around the black hole: the inner accretion disk, the “broad line region” (BLR), and the doughnut-shaped torus. Within the accretion disk, gas and material move at speeds equal to that of a few percent of the speed of light. In the BLR, the speeds of the gas and material slow down to just thousands of kilometers per second, and then subsequently slow down even further in the torus region.
The black hole within NGC 4151 and the different structures of gas and dust surrounding it. (Credit: JAXA)
XRISM’s findings have provided scientists with insight into how black holes grow by “eating” the gas and material surrounding them. Although this isn’t the first time these structures, especially the torus, have been spotted around black holes, the spectroscopic technique employed by XRISM to investigate the movements and speeds of gas and material surrounding the black hole is a first in radio, infrared, and X-ray telescopic observations.
Though XRISM’s first scientific results have been officially published, the telescope’s teams are still working to refine and update instrument performance and data analysis methods on the telescope. To do this, XRISM’s team has selected 60 key targets to observe with the telescope. While teams work on the telescope using these targets, an additional set of 104 new targets was recently selected from over 300 proposals submitted by scientists from across the globe. Fortunately, XRISM’s performance in orbit thus far has been exceptional and has already surpassed initial expectations.
(Lead image: Artist’s impression of the black hole at the center of spiral galaxy NGC 4151. Credit: JAXA)
