system
The Ophiuchus star-forming complex offers an analog for the formation of
the solar system, including the sources of elements found in primitive meteorites

Date:
August 16, 2021
Source:
University of California - Santa Cruz
Summary:
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, a new study of the
Ophiuchus star- forming complex shows how our solar system may
have become enriched with short-lived radioactive elements.



FULL STORY ==========================================================================
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, a new study of the Ophiuchus
star-forming complex shows 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, published August 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 produced in a nearby
cluster of young stars.

Their findings indicate 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 coauthor Douglas
N. C. 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 to use multi- wavelength observations
and a sophisticated statistical analysis to deduce a quantitative
measurement of the model's likelihood." 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.

"These are challenging observations. We can only convincingly detect it
in two star-forming regions, and the best data are from the Ophiuchus
complex," he said.

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
millimeters to gamma rays, the researchers were able to visualize 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." 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 percent chance
it is due to supernovas and a 68 percent 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 said.

The new findings also show that the amount of short-lived radionuclides incorporated into newly forming star systems can vary widely. "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,"
Forbes said. "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." The infrared data, which enabled the team
to peer through dusty clouds into the heart of the star-forming complex,
was obtained by coauthor Joa~o Alves at the University of Vienna as part
of the European Southern Observatory's VISION survey of nearby stellar nurseries using the VISTA telescope in Chile.

"There is nothing special about Ophiuchus as a star formation region,"
Alves said. "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 team also used data from the European Space Agency's
(ESA) Herschel Space Observatory, the ESA's Planck satellite, and NASA's Compton Gamma Ray Observatory.

========================================================================== Story Source: Materials provided by
University_of_California_-_Santa_Cruz. Original written by Tim
Stephens. Note: Content may be edited for style and length.


========================================================================== Journal Reference:
1. John C. Forbes, Joa~o Alves & Douglas N. C. Lin. A Solar System
formation
analogue in the Ophiuchus star-forming complex. Nature Astronomy,
2021 DOI: 10.1038/s41550-021-01442-9 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2021/08/210816112047.htm

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