For the first time, scientists have made clear X-ray detection of chlorine and potassium in stellar debris using data from Japan's XRISM (X-ray Imaging and Spectroscopy Mission) spacecraft.
Decide instrument on board XRISMpronounced “Crisma,” discovered these elements in a supernova remnant called Cassiopeia A, or Cas A for short. The expanding cloud of debris is located about 11,000 light-years away in the northern constellation Cassiopeia.
“This discovery helps illustrate how the death of stars and life on Earth are fundamentally connected,” said Toshiki Sato, an astrophysicist at Meiji University in Tokyo. “Stars appear to twinkle quietly in the night sky, but they are actively creating materials that form planets and support life as we know it. Now, thanks to XRISM, we have a better understanding of when and how stars can create important but hard-to-find elements.”
A paper The result was published on December 4 in the journal Nature Astronomy. Sato led the study along with Kai Matsunaga and Hiroyuki Uchida, both of Kyoto University in Japan. JAXA (Japan Aerospace Exploration Agency) leads XRISM in collaboration with NASA, and also with participation ESA (European Space Agency). NASA and JAXA also jointly developed the Resolve tool.
Stars produce almost all the elements in the universe heavier than hydrogen and helium through nuclear reactions. Heat and pressure transform lighter ones, such as carbon, into heavier ones, such as neon, creating onion-like layers of materials in the interior of stars.
Nuclear reactions also occur during explosive events such as supernovaewhich occur when stars run out of fuel and collapse and explode. The elemental content and arrangement of the debris can respectively tell scientists about the star and its explosion even hundreds or thousands of years later.
Some elements, such as oxygen, carbon and neon, are more common than others and are easier to detect and trace back to a particular stage in a star's life.
Other elements, such as chlorine and potassium, are more elusive. Because scientists have less data about them, it's harder to model where in the star they formed. These rarer elements still play an important role in life on Earth. Potassiumfor example, helps the cells and muscles in our body function, so astronomers are interested in figuring out its cosmic origins.
The roughly circular supernova remnant Cas A is about 10 light-years in size, more than 340 years old, and at its center is a super-dense neutron star – the remnants of the original star's core. Scientists using NASA data Chandra X-ray Observatory used to have identified signs of iron, silicon, sulfur and other elements in Cas A.
Looking for other elements, the team used the Resolve instrument on board XRISM to study the remnant twice in December 2023. The researchers were able to isolate signatures of chlorine and potassium, determining that the residue contained much higher than expected ratios. Resolve also found possible traces of phosphorus, which had previously been detected. discovered to Kas A using infrared missions.
Photo: NASA Goddard Space Flight Center.
“Resolve's high resolution and sensitivity make measurements like this possible,” said Brian Williams, XRISM project scientist at NASA. Goddard Space Flight Center in Greenbelt, Maryland. “Combining the capabilities of XRISM with those of other missions allows scientists to detect and measure these rare elements that are so important to the formation of life in the Universe.”
Astronomers believe that stellar activity may have destroyed layers of nuclear fusion inside the star before it exploded. Such an upheaval could lead to constant large-scale mixing of material inside the star, creating conditions in which chlorine and potassium were produced in abundance.
The scientists also matched Resolve's observations with Chandra's image of Cas A and showed that the elements were concentrated in the southeastern and northern parts of the remnant.
This lopsided distribution could mean that the star itself had an asymmetry before it exploded, as suggested by Chandra's data. indicated earlier this year in a study led by Sato.
“Being able to measure these rarer elements with good statistical precision really helps us understand the nuclear fusion that occurs in stars before and during supernovae,” said co-author Paul Pluczynski, an astrophysicist at Center for Astrophysics | Harvard and Smithsonian Institution in Cambridge, Massachusetts. “We suspected that asymmetry might be a key part, and now we have more evidence of that. But there's still a lot we don't understand about how stars explode and distribute all these elements throughout the cosmos.”
TO Jeanette Kazmierczak
NASA Goddard Space Flight CenterGreenbelt, Maryland.
Media contact:
Claire Andreoli
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NASA Goddard Space Flight Center, Greenbelt, Maryland.
