Nearby star-forming region yields clues to the formation of our solar system

A region of active star formation in the constellation Ophiuchus gives astronomers new insights into the formation conditions of our own solar system. In particular, a new study of the star formation complex Ophiuchus shows how our solar system could have been enriched with short-lived radioactive elements.

Evidence for this enrichment process has existed since the 1970s when scientists studying certain mineral inclusions in meteorites concluded that they were pristine remnants of the young solar system and contained the decay products of short-lived radionuclides. These radioactive elements could have been blown onto the nascent solar system by a nearby exploding star (a supernova) or by the strong stellar winds of a massive star known as the Wolf-Rayet star.

The authors of the new study, published Aug. 16 in Nature Astronomy, used multi-wavelength observations of the Ophiuchus star-forming region, including spectacular new infrared data, to reveal interactions between the clouds of star-forming gas and radionuclides found in a nearby cluster of young Stars. Their results suggest that supernovae in the star cluster are the most likely source of short-lived radionuclides in the star formation clouds.

“Our solar system was most likely formed in a giant molecular cloud along with a young star cluster, and one or more supernova events from some massive stars in that cluster contaminated the gas that turned into the sun and its planetary system,” said co-author Douglas NC Lin, Professor Emeritus of Astronomy and Astrophysics at UC Santa Cruz. “Although this scenario has been suggested in the past, the strength of this paper is that it uses multiple wavelength observations and sophisticated statistical analysis to derive a quantitative measure of the likelihood of the model.”

First author John Forbes of the Flatiron Institute’s Center for Computational Astrophysics said data from space-based gamma-ray telescopes enables the detection of gamma rays emitted by the short-lived radionuclide aluminum-26. “These are challenging observations. We can only convincingly demonstrate it in two star-forming regions, and the best data come from the Ophiuchus complex, ”he said.

The Ophiuchus cloud complex contains many dense protostellar nuclei in various stages of star formation and protoplanetary disk evolution, which represent the earliest stages in the formation of a planetary system. By combining image data in the wavelength range from millimeters to gamma rays, the researchers were able to visualize an aluminum-26 flow from the nearby star cluster towards the Ophiuchus star-forming region.

“The enrichment process we see in Ophiuchus is consistent with what happened during the formation of the solar system 5 billion years ago,” Forbes said. “When we saw this beautiful example of how the process might go, we tried to model the nearby star cluster that produced the radionuclides we see today in gamma rays.”

Forbes developed a model that takes into account every massive star that could have existed in this region, including its mass, age, and probability of exploding as a supernova, and takes into account the potential yields of aluminum-26 from stellar winds and supernovae. The model enabled him to determine the probabilities of various scenarios observed today for the manufacture of the aluminum-26.

“We now have enough information to say that there is a 59 percent chance of supernovae and a 68 percent chance of multiple sources, not just one,” Forbes said.

This type of statistical analysis assigns probabilities to scenarios that astronomers have debated over the past 50 years, Lin noted. “This is the new direction for astronomy to quantify probability,” he said.

The new findings also show that the amount of short-lived radionuclides that are incorporated into newly emerging star systems can vary widely. “Many new star systems are born with aluminum-26 abundances in line with our solar system, but the variation is huge – several orders of magnitude,” Forbes said. “This is important for the early development of planetary systems, since aluminum-26 is the most important early heat source. More aluminum-26 probably means drier planets. “

The infrared data, which enabled the team to look through dusty clouds into the heart of the star formation complex, were collected using VISTA by co-author João Alves from the University of Vienna as part of the VISION study of nearby star kindergartens run by the European Southern Observatory. won telescope in Chile.

“Ophiuchus as a star-forming region is nothing special,” said Alves. “It’s just a typical configuration of gas and young massive stars, so our results should be representative of the accumulation of short-lived radioactive elements in the formation of stars and planets in the Milky Way.”

The team also used data from the European Space Agency’s (ESA) Herschel Space Observatory, ESA’s Planck satellite, and NASA’s Compton gamma-ray observatory.

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