At the heart of our galaxy lies a supermassive black hole, a formidable entity that consumes any matter that ventures too close. However, recent data from the JWST reveals that in the vicinity of this cosmic giant, a dying star is still expelling matter into space.
While some stars end their lives as dazzling supernovae, outshining entire galaxies, not all stars meet such an explosive fate. Stars with up to eight times the mass of our Sun become large, reddish, and cool, shedding their outer layers over time, eventually transforming into white dwarfs, or perhaps even ‘celestial diamonds.’
Regardless of whether stars conclude their existence in explosive supernovae or slowly fade away, their demise gives rise to new life, a concept famously encapsulated by Carl Sagan’s phrase, “We are made of star-stuff.”
Using the JWST, astronomers have identified significant star-stuff, including water, dust, and oxygen-based chemical products, under extreme conditions.
“Galactic centers are among the most extreme environments, so understanding whether stars can continue enriching their surroundings there is an important question,” explains Florian PeiĂźker, an astrophysicist at the University of Cologne in Germany and lead author of a study detailing this discovery.
“With Webb, we can directly observe how stars behave under these conditions and see that dust production remains remarkably resilient.”
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The researchers examined the inner parsec, a 3.26-light-year stretch of the Milky Way, using JWST’s Mid-Infrared Instrument (MIRI), focusing on a particularly luminous dying star known as IRS 3.
Named for its infrared emissions, IRS 3 is an asymptotic giant branch (AGB) star, a later life stage of stellar evolution.
The star’s intense stellar winds propel its outer layers into space at approximately 15 kilometers (9 miles) per second. This has enveloped the star in a vast cloud of dust extending 10,000 astronomical units (AU), with one AU equaling the distance between Earth and the Sun, roughly 150 million kilometers.
IRS 3 is located a mere 0.55 light-years from Sagittarius A*, the massive black hole at the dynamic center of the Milky Way.
As previously mentioned, the star’s final stages contribute to the cosmic dust around it. However, astronomers have questioned whether this process could occur so close to a supermassive black hole. To address this, they conducted several simulations to align JWST’s findings with models of stars featuring diverse temperatures, luminosities, and chemical compositions.
Based on these models and observations, including the bow shock formed as the star’s envelope collides with interstellar space, researchers deduced key properties of IRS 3. It may have originated as far as 16 light-years from the galactic center before migrating inward. IRS 3 might be about six times more massive than the Sun and approximately 72 million years old, relatively young compared to the Sun’s anticipated 10-billion-year lifespan.
Although IRS 3’s effective temperature is a modest 2800 K (about 4,600 degrees Fahrenheit or 2,500 degrees Celsius), compared to the Sun’s surface temperature of 5,500 °C, it shines with a brightness 60,000 times greater.
This research highlights that even in harsh conditions, stars like IRS 3 can continue to provide chemically rich dust and water to galactic centers. “This is the first time a continuous mid-infrared spectrum has been collected for this star, allowing us to detect the features from the silicate dust and uncover the star’s true chemical identity,” says Macarena Garcia Marin, an ESA scientist for Webb’s MIRI instrument and one of the study’s co-authors.
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As the star nears the end of its life, it intermittently expels its outer layers, forming layers of shells over hundreds of years, potentially dating back 5,000 years, according to a previous study. “The detection of water is especially exciting because it shows that molecular material can survive in an environment dominated by intense radiation,” says Garcia Marin.
Related: There May Be 170 Million Black Holes Lurking in The Milky Way’s Graveyard
When water and other star-derived materials are mixed with radiation, the cosmic processes can create unexpected phenomena. “This tells us that even close to a supermassive black hole, stars can continue contributing material back into their surroundings,” Garcia Marin concludes.
This research was published in Astronomy & Astrophysics.
This article was fact-checked by Clare Watson and edited by Rebecca Dyer. While we pride ourselves on our process, we are only human. If you spot a mistake, please let us know.
