Study finds new clues regarding formation of solar system

A study of the Ophiuchus star-forming complex has offered new insights into the conditions in which our own solar system was born.

The findings of the study were published in the journal 'Nature Astronomy'. A region of active star formation in the constellation Ophiuchus is giving astronomers new insights into the conditions in which our own solar system was born.

In particular, the study showed how our solar system may have become enriched with short-lived radioactive elements.

Evidence of this enrichment process has been around since the 1970s when scientists studying certain mineral inclusions in meteorites concluded that they were pristine remnants of the infant 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 from a type of massive star known as a Wolf-Rayet star.

The authors of the new study 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 produced in a nearby cluster of young stars.

Their findings indicated that supernovas in the star cluster are the most likely source of short-lived radionuclides in the star-forming clouds.

"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," said co-author Douglas NC Lin, professor emeritus of astronomy and astrophysics at UC Santa Cruz.

First author John Forbes at the Flatiron Institute's Center for Computational Astrophysics said data from space-based gamma-ray telescopes enable the detection of gamma rays emitted by the short-lived radionuclide aluminum-26.

The Ophiuchus cloud complex contains many dense protostellar cores in various stages of star formation and protoplanetary disk development, representing the earliest stages in the formation of a planetary system.

By combining imaging data in wavelengths ranging from millimetres to gamma rays, the researchers were able to visualise a flow of aluminum-26 from the nearby 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," Forbes said.

"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," he added.

Forbes developed a model that accounts for every massive star that could have existed in this region, including its mass, age, and probability of exploding as a supernova, and incorporates the potential yields of aluminum-26 from stellar winds and supernovas.

The model enabled him to determine the probabilities of different scenarios for the production of the aluminum-26 observed today.

"We now have enough information to say that there is a 59 per cent chance it is due to supernovas and a 68 per cent chance that it's from multiple sources and not just one supernova," Forbes said.

This type of statistical analysis assigns probabilities to scenarios that astronomers have been debating for the past 50 years, Lin noted.

"This is the new direction for astronomy, to quantify the likelihood," he added.