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| An image of the Milky Way from the MeerKAT radio telescope puts the James Webb Space Telescope’s Sagittarius C image in context, revealing supernova remnants and the bright core around the galaxy’s supermassive black hole, with massive vertical filaments echoing Webb’s findings in the hydrogen cloud. |
A recent follow-up study on an image of the Sagittarius C stellar nursery, captured by NASA’s James Webb Space Telescope, has provided new revelations about the enigmatic processes of star formation in the heart of our Milky Way galaxy. The findings highlight key phenomena, including ejections from still-forming protostars and the impact of powerful magnetic fields on the interstellar gas, which may explain the relatively low star formation rates in this region despite its dense clouds of gas and cosmic dust.
Astrophysicist John Bally of the University of Colorado Boulder, one of the lead researchers of the study, noted, “A big question in the Central Molecular Zone of our galaxy has been, if there is so much dense gas and cosmic dust here, and we know that stars form in such clouds, why are so few stars born here?” His team’s breakthrough research suggests that the strong magnetic fields present in this region may play a significant role in suppressing star formation.
The crowded and dusty environment of Sagittarius C has posed challenges for scientists attempting to study its young stars. However, the advanced infrared capabilities of Webb’s instruments have allowed astronomers to peer through the dense clouds and study these nascent stars in unprecedented detail.
“The extreme environment of the galactic center is a fascinating place to put star formation theories to the test, and the infrared capabilities of NASA’s James Webb Space Telescope provide the opportunity to build on past important observations from ground-based telescopes like ALMA and MeerKAT,” said Samuel Crowe, another principal investigator in the research and a senior undergraduate at the University of Virginia.
Two major papers from Bally and Crowe, both published in The Astrophysical Journal, detailed these groundbreaking discoveries.
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| The star-forming region Sagittarius C, about 200 light-years from the Milky Way’s supermassive black hole, Sagittarius A*, uses color coding in the James Webb Space Telescope’s image, where infrared data is shifted to visible light, with shorter wavelengths in blue and longer ones in red. |
Using Infrared to Unveil Forming Stars.
The research team utilized Webb’s near-infrared capabilities to confirm the formation of two massive protostars in the brightest cluster of Sagittarius C. These protostars are already more than 20 times the mass of our Sun, a significant finding that aligns with previous tentative results from the Atacama Large Millimeter Array (ALMA). Webb also revealed powerful outflows from each of these massive stars.
Identifying low-mass protostars, which are still enveloped in thick cocoons of cosmic dust, proved to be a more difficult task. However, by comparing Webb’s data with past ALMA observations, the team identified five promising candidates for low-mass protostars.
Additionally, the researchers discovered 88 features that appear to be shocked hydrogen gas, formed where material ejected from young stars collides with the surrounding gas cloud. This led to the identification of a new star-forming cloud distinct from the main Sagittarius C cloud, containing at least two protostars that are generating their own jets.
“The confirmation of these outflows in infrared light is very exciting,” said Crowe. “There is still so much we don’t know about star formation, particularly in the Central Molecular Zone, and understanding this region is crucial to understanding how our universe functions.”
The Role of Magnetic Fields in Star Formation.
One of the most striking features in the 2023 image of Sagittarius C captured by Webb is the presence of numerous filaments within a region of hot hydrogen plasma. Bally and his team suggest that these filaments are shaped by magnetic fields, which have been observed in previous studies by ground-based telescopes like ALMA and MeerKAT.
“The motion of gas swirling in the extreme tidal forces of the Milky Way’s supermassive black hole, Sagittarius A*, can stretch and amplify the surrounding magnetic fields,” explained Bally. “These amplified fields are likely shaping the plasma in Sagittarius C.”
The researchers propose that the strong magnetic fields in the galactic center could be powerful enough to prevent the plasma from dispersing, instead confining it into the distinct filaments observed in the Webb image. These fields might also resist the gravitational forces that would otherwise cause the gas and dust clouds to collapse and form new stars, helping to explain the surprisingly low rate of star formation in this dense region.
“This is an exciting area for future research,” said Crowe. “The role of strong magnetic fields in stellar ecology, both in the center of our galaxy and in other galaxies, has not been fully explored.”
The James Webb Space Telescope’s Role in Advancing Astrophysics.
The James Webb Space Telescope continues to make significant contributions to our understanding of the universe. Webb is uncovering mysteries in our solar system, studying exoplanets in distant star systems, and providing new insights into the complex structures and origins of the cosmos. Webb is an international project led by NASA, in partnership with the European Space Agency (ESA) and the Canadian Space Agency (CSA).
These recent discoveries offer a fresh perspective on star formation in one of the most challenging environments known, highlighting the importance of Webb’s infrared capabilities in expanding our knowledge of the cosmos. As research continues, the impact of magnetic fields on star formation could become a critical focus in understanding the life cycle of stars, not just in our galaxy, but throughout the universe.