Ophiuchus Star-Forming Complex Could be an Analog for Solar System Formation

Astronomers have gained a better understanding of the conditions in which the solar system originated. This insight was offered by the constellation Ophiuchus, a zone of active star formation.

Specifically, a new investigation of the Ophiuchus star-forming complex displays how the solar system might have been enriched with short-lived radioactive elements.

Proof for this enrichment process has been there since the 1970s when researchers investigating a few mineral inclusions in meteorites came to a conclusion that they were pristine remnants of the infant solar system and included the decay products of short-lived radionuclides.

Such radioactive elements could have been thrust onto the nascent solar system by an exploding star (a supernova) in the vicinity or by the powerful stellar winds from a kind of massive star called a Wolf-Rayet star.

The researchers involved in the new study made use of multi-wavelength observations of the Ophiuchus star-forming region, such as spectacular new infrared data, to unravel interactions between the clouds of star-forming gas and radionuclides generated in a proximate cluster of young stars.

The study outcomes denote that the supernovas in the star cluster are probably the source of short-lived radionuclides in the star-forming clouds. The study was reported in the Nature Astronomy journal on August 16^th, 2021.

Our solar system was most likely formed in a giant molecular cloud together with a young stellar cluster and one or more supernova events from some massive stars in this cluster contaminated the gas which turned into the sun and its planetary system.

Douglas N. C. Lin, Study Co-Author and Professor Emeritus of Astronomy and Astrophysics, University of California Santa Cruz

“Although this scenario has been suggested in the past, the strength of this paper is to use multi-wavelength observations and a sophisticated statistical analysis to deduce a quantitative measurement of the model’s likelihood,” added Lin.

John Forbes, the first author of the study from the Flatiron Institute’s Center for Computational Astrophysics, said that the data obtained from space-based gamma-ray telescopes facilitate the detection of gamma rays discharged by the short-lived radionuclide called aluminum-26.

“These are challenging observations. We can only convincingly detect it in two star-forming regions, and the best data are from the Ophiuchus complex,” stated Lin.

The Ophiuchus cloud complex includes several dense protostellar cores in different stages of star formation and protoplanetary disk development. This constitutes the initial stages in the formation of a planetary system.

Integrating imaging data in wavelengths, varying from millimeters to gamma rays, helped scientists observe a flow of aluminum-26 from the proximate star cluster toward the Ophiuchus star-forming region.

The enrichment process we’re seeing in Ophiuchus is consistent with what happened during the formation of the solar system 5 billion years ago. Once we saw this nice example of how the process might happen, we set about trying to model the nearby star cluster that produced the radionuclides we see today in gamma rays.

John Forbes, Study First Author, Center for Computational Astrophysics, Flatiron Institute

A new model developed by Forbes considers each massive star that could have occurred in this region, such as its age, mass and likelihood of exploding as a supernova. Furthermore, it integrates the potential yields of aluminum-26 from stellar winds and supernovas. The model allowed Forbes to identify the possibilities of various scenarios for producing the aluminum-26 noted now.

“We now have enough information to say that there is a 59 percent chance it is due to supernovas and a 68 percent chance that it’s from multiple sources and not just one supernova,” stated Forbes.

According to Lin, this kind of statistical analysis assigns prospects to scenarios debated by astronomers in the past five decades. “This is the new direction for astronomy, to quantify the likelihood,” stated Lin.

Furthermore, the results of the new study demonstrate that the amount of short-lived radionuclides integrated into newly forming star systems can differ substantially.

Many new star systems will be born with aluminum-26 abundances in line with our solar system, but the variation is huge—several orders of magnitude. This matters for the early evolution of planetary systems, since aluminum-26 is the main early heating source. More aluminum-26 probably means drier planets.

John Forbes, Study First Author, Center for Computational Astrophysics, Flatiron Institute

The infrared data that helped the researchers peer through dusty clouds into the center of the star-forming complex was achieved by coauthor João Alves at the University of Vienna as part of the European Southern Observatory’s VISION survey of proximate stellar nurseries with the help of the VISTA telescope in Chile.

Alves stated, “There is nothing special about Ophiuchus as a star formation region. It is just a typical configuration of gas and young massive stars, so our results should be representative of the enrichment of short-lived radioactive elements in star and planet formation across the Milky Way.”

The researchers utilized the information gathered from the European Space Agency’s (ESA) Herschel Space Observatory, the ESA’s Planck satellite and NASA’s Compton Gamma Ray Observatory.

Journal Reference:

Forbes, J. C., et al. (2021) A Solar System formation analog in the Ophiuchus star-forming complex. Nature Astronomy. doi.org/10.1038/s41550-021-01442-9.