NASA’s James Webb Space Telescope has made a groundbreaking discovery, capturing a blowtorch-like eruption of gasses from a massive protostar located in the nebula Sharpless 2-284 (Sh2-284).
This spectacular stellar jet stretches across an astonishing 8 light-years, roughly twice the distance between the Sun and the nearest star system, Alpha Centauri.
Researchers have deemed this particular stellar outflow rare due to its immense size and strength, with the central protostar weighing as much as ten times the mass of our Sun, situated 15,000 light-years away in the outer reaches of our galaxy.
Lead author Yu Cheng of the National Astronomical Observatory of Japan remarked on the serendipitous nature of the Webb discovery, stating, “We didn’t really know there was a massive star with this kind of super-jet out there before the observation.”
He notes that such a spectacular outflow of molecular hydrogen from a massive star is uncommon in other regions of our galaxy.
The remarkable stellar jet, which stretches across space at hundreds of thousands of miles per hour, creates an optical effect resembling a double-bladed dueling lightsaber from the popular Star Wars franchise.
Stellar jets are known to be highly collimated streams of plasma that shoot out from newly forming stars, serving as a cosmic “birth announcement” to the universe.
The outflow is a result of gas collapsing around the protostar and is likely influenced by magnetic fields as material is expelled along the star’s spin axis.
Although hundreds of protostellar jets have been observed, most are from low-mass stars.
These jets provide valuable insight into the nature of newly forming stars, with their energetics, narrowness, and evolutionary time scales helping to refine models of both the environment and the physical properties surrounding the young star at the center of the outflow.
Co-author Jonathan Tan from the University of Virginia and Chalmers University of Technology shared his astonishment upon first seeing the jet’s order, symmetry, and size: “I was really surprised at the order, symmetry, and size of the jet when we first looked at it.”
The remarkable discovery adds to the understanding that protostellar jets scale up in size with the mass of the star generating them.
The larger the star, the more substantial the outflow, as suggested by the detailed filamentary structure observed in Webb’s infrared images.
These images indicate that the jet is interacting with interstellar dust and gas, producing distinct knots, bow shocks, and linear chains in its wake.
The tips of the jet, which are positioned in opposite directions, encapsulate the star’s formation history, revealing that material once close to the star has spread outward over 100,000 years, creating an older outflow in the process.
The host proto-cluster, where this intense stellar jet originates, is found nearly twice as far from the galactic center as our Sun, placing it within the outskirts of the Milky Way galaxy.
Within this cluster, hundreds of stars continue to form, and due to its location in the galactic periphery, these stars exhibit deficiencies in heavier elements beyond hydrogen and helium, characterized as low metallicity.
Low metallicity reflects a relatively pristine environment analogous to conditions present in the early universe, prior to the formation of heavier elements through stellar processes like nuclear fusion and supernovae.
Cheng emphasizes the significance of massive stars in the evolutionary process of galaxies, suggesting that this discovery aids in illuminating the formation mechanisms of massive stars within low-metallicity environments.
He notes, “Our discovery is shedding light on the formation mechanism of massive stars in low metallicity environments, so we can use this massive star as a laboratory to study what was going on in earlier cosmic history.”
The formation of massive stars is believed to be influenced by gravitational energy released as the stars grow in mass, with stellar jets encoding their formation history as they emerge.
Tan elaborated, “Webb’s new images are telling us that the formation of massive stars in such environments could proceed via a relatively stable disk around the star that is expected in theoretical models of star formation known as core accretion.”
Through the observations captured by Webb, the team has developed new theoretical models of core accretion, suggesting that the central star is approximately ten times larger than the Sun and is still undergoing growth as it powers the massive outflow.
For over three decades, astronomers have debated the methods by which massive stars form. Some proponents of the competitive accretion model argue that such formation necessitates a chaotic process where material falls from various directions, causing the disk’s orientation to shift over time.
In this case, the outflows generated would appear to twist and turn inconsistently due to competitive accretion dynamics.
However, the findings from Webb reveal a nearly symmetrical configuration of the jets, with opposite sides positioned approximately 180 degrees apart.
Tan emphasizes that such stability reinforces core accretion theory, noting that it indicates the central disk is held steady.
Cheng suggests that where one massive star is found, there could very well be others in the outer reaches of the Milky Way still in earlier stages of formation, potentially emitting jets not yet observable.
The Atacama Large Millimeter Array in Chile also contributed data suggesting the presence of another dense stellar core possibly in the initial stages of construction.
This groundbreaking research has been accepted for publication in The Astrophysical Journal, marking a significant contribution to the field of astrophysics.
As a premier space science observatory, the James Webb Space Telescope continues to unravel the mysteries of our solar system, investigate distant exoplanets, and probe the origins and structure of the universe.
The Webb mission is a collaboration between NASA, the European Space Agency (ESA), and the Canadian Space Agency (CSA).
To learn more about the James Webb Space Telescope and its discoveries, visit https://science.nasa.gov/webb.
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