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A potential discovery of a dark galaxy composed mainly of dark matter has emerged from observations in the local universe. Dark galaxies are hypothesized to be starless systems whose identification could significantly enhance our understanding of galaxy formation processes.
The new candidate for a dark galaxy has been located within a large, rapidly moving gas cloud, which has been observed since the 1960s. High-resolution data shared in a recent study published in Science Advances indicates a compact gas clump that may qualify as a dark galaxy.
Astronomer Jin-Long Xu from the Chinese Academy of Sciences in Beijing remarked, “This is the first discovery of a potential dark galaxy in the nearby universe.” However, skepticism remains among some members of the astronomical community. Tobias Westmeier from the University of Western Australia expressed caution, suggesting that the evidence might be insufficient to classify the clump definitively as a dark galaxy. He posits that it could instead be a conventional gas cloud located at the Milky Way’s outskirts, stating, “There’s no convincing evidence.”
Since the early 2000s, several candidates for dark galaxies have been noted around the Milky Way, yet many have ultimately been reclassified upon further observation. Instances of initially overlooked faint stars have often distinguished these misidentified galaxies. Westmeier notes, “People have been trying to find these starless galaxies for many years and so far without much success.”
The recent findings stem from analyses conducted using three radio telescopes, including data from China’s Five-hundred-meter Aperture Spherical Telescope. These observations revealed that the clump contains hydrogen gas, which is detectable through radio wavelengths. Additionally, information from two stellar surveys indicated the absence of stars within the clump.
Researchers analyzed the radio telescope data to ascertain the speed and direction of hydrogen movement, also allowing them to estimate the distance to the clump at about 900,000 light-years from Earth. The rotational dynamics observed in the clump’s gas suggest it could resemble a disk galaxy, as opposed to merely a gas cloud.
Ming Zhu, another co-author of the study from the Chinese Academy of Sciences, shared enthusiasm about the identification of a rotating disk structure within the clump. Yet, Westmeier cautioned that errors in distance estimation could lead to misinterpretations of the observed rotational features. Zhu concurred, underscoring the necessity for more accurate distance assessments and finer resolution data to validate the candidate as a bona fide dark galaxy.
Theories suggest that dark galaxies might serve as foundational components in the evolution of larger galaxies. It is believed that as dark galaxies interact with starry counterparts, their gaseous mass encourages star formation. They may also arise from regular galaxies that have experienced stellar loss due to collision interactions. The team behind the latest study theorizes that their potential dark galaxy formed by colliding with surrounding intergalactic gas.
Ultimately, the discovery of dark galaxies could advance astronomers’ computer simulations, improving their models of galaxy formation and evolution. Additionally, studying these structures may provide insights into the composition of dark matter itself. Xu emphasizes the significance of this discovery in confirming whether galaxy formation initiates with dark galaxies, stating, “Dark galaxies are the most primitive state of a general galaxy formation.”
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