From University of California-Santa Cruz (US) : “Nearby star-forming region yields clues to the formation of our solar system”

From University of California-Santa Cruz (US)

August 16, 2021
Tim Stephens

Multi-wavelength observations of the Ophiuchus star-forming region reveal interactions between clouds of star-forming gas and radionuclides produced in a nearby cluster of young stars. The top image (a) shows the distribution of aluminum-26 in red, traced by gamma-ray emissions. The central box represents the area covered in the bottom left image (b), which shows the distribution of protostars in the Ophiuchus clouds as red dots. The area in the box is shown in the bottom right image (c), a deep near-infrared color composite image of the L1688 cloud, containing many well known prestellar dense-gas cores with disks and protostars (see larger image below). (Credit: Forbes et al., Nature Astronomy 2021.)

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 João 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.

See the full article here .


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UC Santa Cruz (US) Lick Observatory Since 1888 Mt Hamilton, in San Jose, California, Altitude 1,283 m (4,209 ft)

UC Observatories Lick Automated Planet Finder fully robotic 2.4-meter optical telescope at Lick Observatory, situated on the summit of Mount Hamilton, east of San Jose, California, USA.

The UCO Lick C. Donald Shane telescope is a 120-inch (3.0-meter) reflecting telescope located at the Lick Observatory, Mt Hamilton, in San Jose, California, Altitude 1,283 m (4,209 ft).
UC Santa Cruz (US) campus.

The University of California-Santa Cruz (US) , opened in 1965 and grew, one college at a time, to its current (2008-09) enrollment of more than 16,000 students. Undergraduates pursue more than 60 majors supervised by divisional deans of humanities, physical & biological sciences, social sciences, and arts. Graduate students work toward graduate certificates, master’s degrees, or doctoral degrees in more than 30 academic fields under the supervision of the divisional and graduate deans. The dean of the Jack Baskin School of Engineering oversees the campus’s undergraduate and graduate engineering programs.

UCSC is the home base for the Lick Observatory.

UCO Lick Observatory’s 36-inch Great Refractor telescope housed in the South (large) Dome of main building.

Search for extraterrestrial intelligence expands at Lick Observatory
New instrument scans the sky for pulses of infrared light
March 23, 2015
By Hilary Lebow

Astronomers are expanding the search for extraterrestrial intelligence into a new realm with detectors tuned to infrared light at UC’s Lick Observatory. A new instrument, called NIROSETI, will soon scour the sky for messages from other worlds.

“Infrared light would be an excellent means of interstellar communication,” said Shelley Wright, an assistant professor of physics at UC San Diego (US) who led the development of the new instrument while at the U Toronto Dunlap Institute for Astronomy and Astrophysics (CA).

Shelley Wright of UC San Diego with (US) NIROSETI, developed at U Toronto Dunlap Institute for Astronomy and Astrophysics (CA) at the 1-meter Nickel Telescope at Lick Observatory at UC Santa Cruz

Wright worked on an earlier SETI project at Lick Observatory as a UC Santa Cruz undergraduate, when she built an optical instrument designed by University of California-Berkeley (US) researchers. The infrared project takes advantage of new technology not available for that first optical search.

Infrared light would be a good way for extraterrestrials to get our attention here on Earth, since pulses from a powerful infrared laser could outshine a star, if only for a billionth of a second. Interstellar gas and dust is almost transparent to near infrared, so these signals can be seen from great distances. It also takes less energy to send information using infrared signals than with visible light.

Frank Drake, professor emeritus of astronomy and astrophysics at UC Santa Cruz and director emeritus of the SETI Institute, said there are several additional advantages to a search in the infrared realm.

Frank Drake with his Drake Equation. Credit Frank Drake.

“The signals are so strong that we only need a small telescope to receive them. Smaller telescopes can offer more observational time, and that is good because we need to search many stars for a chance of success,” said Drake.

The only downside is that extraterrestrials would need to be transmitting their signals in our direction, Drake said, though he sees this as a positive side to that limitation. “If we get a signal from someone who’s aiming for us, it could mean there’s altruism in the universe. I like that idea. If they want to be friendly, that’s who we will find.”

Scientists have searched the skies for radio signals for more than 50 years and expanded their search into the optical realm more than a decade ago. The idea of searching in the infrared is not a new one, but instruments capable of capturing pulses of infrared light only recently became available.

“We had to wait,” Wright said. “I spent eight years waiting and watching as new technology emerged.”

Now that technology has caught up, the search will extend to stars thousands of light years away, rather than just hundreds. NIROSETI, or Near-Infrared Optical Search for Extraterrestrial Intelligence, could also uncover new information about the physical universe.

“This is the first time Earthlings have looked at the universe at infrared wavelengths with nanosecond time scales,” said Dan Werthimer, UC Berkeley SETI Project Director. “The instrument could discover new astrophysical phenomena, or perhaps answer the question of whether we are alone.”

NIROSETI will also gather more information than previous optical detectors by recording levels of light over time so that patterns can be analyzed for potential signs of other civilizations.

“Searching for intelligent life in the universe is both thrilling and somewhat unorthodox,” said Claire Max, director of UC Observatories and professor of astronomy and astrophysics at UC Santa Cruz. “Lick Observatory has already been the site of several previous SETI searches, so this is a very exciting addition to the current research taking place.”

NIROSETI will scan the skies several times a week on the Nickel 1-meter telescope at Lick Observatory, located on Mt. Hamilton east of San Jose.