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The endeavor, spearheaded by the Japanese Aerospace Exploration Agency and NASA, aims to illuminate a vital element for life
A global collection of researchers has offered an extraordinary assessment of elemental sulfur dispersed among the stars by analyzing data from the XRISM spacecraft, overseen by Japan.
“Sulfur plays a crucial role in how cells operate in our bodies here on Earth, yet numerous questions remain regarding its presence in the universe,” stated Lía Corrales, an assistant professor of astronomy at the University of Michigan.
Astronomers employed X-rays from two binary star systems to discover sulfur in the interstellar medium, the gaseous and dusty matter located in the voids between stars. This marks the initial direct quantification of both gaseous and solid phases of sulfur, showcasing the unique capabilities of X-ray spectroscopy, XRISM’s main technique for exploring the universe.
“Sulfur can swiftly transition between gas and solid states,” Corrales remarked. “The XRISM spacecraft delivers the resolution and sensitivity necessary to detect it in both forms and gain insights into where it might be concealed.”
A publication detailing these findings, led by Corrales, was released on June 27 in the Publications of the Astronomical Society of Japan.
By utilizing ultraviolet light, specialists have detected gaseous sulfur in the void between stars. In denser regions of the interstellar medium, such as the molecular clouds where stars and planets originate, this sulfur form vanishes rapidly. Researchers surmise that the sulfur solidifies, possibly bonding with ice or combining with other elements.
When a physician conducts an X-ray on Earth, they position the patient between an X-ray emitter and a receptor. Bones and tissues absorb varying degrees of light as it flows through the patient’s body, crafting contrast in the receptor. To examine sulfur, Corrales and her team implemented a similar approach.
They selected an area of the interstellar medium with appropriate density—not so sparse that all X-rays would pass through undiminished, yet not so dense that they would be entirely absorbed.
The team then identified a luminous X-ray source situated behind that section of the medium, a binary star system known as GX 340+0, positioned over 35,000 light-years away in the southern constellation Scorpius.
With the Resolve instrument aboard XRISM, researchers could gauge the energy of X-rays emitted by GX 340+0 and identified that sulfur existed not only as a gas but also as a solid, potentially amalgamated with iron.
“Chemical processes in environments like the interstellar medium differ significantly from what we experience on Earth, but we’ve modeled sulfur combined with iron, and it appears to align with what we’re observing with XRISM,” remarked co-author Elisa Costantini, a senior astronomer at the Space Research Organization Netherlands and the University of Amsterdam. “Our research division has created models for various elements to compare with astronomical findings for years. This project is ongoing, and shortly, we will have new sulfur measurements to compare with the XRISM data to enhance our understanding.”
Iron-sulfur compounds frequently appear in meteorites, leading scientists to speculate that this may be one mechanism in which sulfur solidifies from molecular clouds and navigates through the cosmos.
In their publication, Corrales and her colleagues suggest several compounds that would correspond with XRISM’s observations—pyrrhotite, troilite, and pyrite, often referred to as fool’s gold. The researchers also utilized data from a second X-ray binary labeled 4U 1630-472, which further validated their conclusions.
“NASA’s Chandra X-ray Observatory has previously investigated sulfur, but XRISM’s observations are the most comprehensive to date,” noted Brian Williams, the XRISM project scientist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland. “As GX 340+0 is located on the opposite side of the galaxy from our position, XRISM’s X-ray measurements serve as a unique examination of sulfur across a vast area of the Milky Way. There remains a wealth of knowledge to uncover about the galaxy we inhabit.”
XRISM is managed by JAXA, the Japan Aerospace Exploration Agency, in collaboration with NASA and contributions from the European Space Agency (ESA). NASA and JAXA designed Resolve, the mission’s microcalorimeter spectrometer.
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