ReportWire

Tag: The Milky Way

  • After Decades of Searching, Scientists Make a Major Breakthrough in the Mystery Surrounding Our Galaxy’s Black Hole

    [ad_1]

    Every large galaxy harbors a supermassive black hole at its center, each one emitting powerful winds of hot gas from its event horizon. Our galaxy should be no exception. Yet for the last 50 or so years, astronomers have been searching for winds coming from the black hole at the Milky Way’s center, and in all that time, they found nothing. Not even a gentle breeze.

    Until now. In a preliminary study, a team of scientists detail the strongest evidence found yet of winds flowing from the Milky Way’s black hole, Sagittarius A*. The breakthrough findings, posted to the preprint server arXiv in September, describe a large, cone-shaped region around the black hole where cold gas appears to have been blown away.

    “If this is true, then it would be a very exciting discovery with some pretty broad implications for the center of our galaxy,” Lia Hankla, a postdoctoral astrophysicist at the University of Maryland who was not involved in the study, told Science. While she notes that the missing gas is indirect evidence of the black hole’s wind, the findings are a major step forward in solving this case.

    Hunting for the winds of Sagittarius A*

    Contrary to popular belief, black holes don’t just suck up everything that comes too close. As gas spirals into the disk of material surrounding a supermassive black hole, it heats up. Through a complex combination of magnetic, radiation, and thermal effects, some of this gas gets belched out in the form of winds or high-speed jets of plasma.

    A supermassive black hole’s winds are so powerful, they shape how its host galaxy evolves. Astronomers know, for example, that the winds help keep intergalactic gas hot and suppress star formation, limiting the galaxy from growing too big. Understanding how these dynamics are playing out at the center of the Milky Way is key to knowing how it evolved over time, and to tracing our own origin story.

    Many an astronomer has searched for Sagittarius A*’s winds, but previous telescope observations have yielded conflicting results, largely because its just hard to peer through all the gas, dust, and stars that shroud the galactic nucleus.

    In this new study, however, a new telescope in Chile has risen to the occasion. The Atacama Large Millimeter/Submillimeter Array (ALMA) is the most powerful radio telescope in the world. Compared to optical telescopes, it’s exceptionally good at penetrating clouds of dust.

    How they did it

    Astrophysicist Lena Murchikova and astronomer Mark Gorski, both of Northwestern University, combined about five years of ALMA observations with state-of-the-art data processing techniques to produce an unprecedentedly detailed map of the cold molecular gas around Sagittarius A*.

    This map revealed a cone-shaped gap in the cold gas cloud. When the researchers overlaid their map onto X-ray data gathered by NASA’s Chandra X-ray Observatory, it matched the cone shape perfectly. The alignment suggests that hot plasma wind emanating from Sagittarius A* is blowing cold gas away, and emitting X-rays in the process.

    The findings bring scientists closer than ever to solving the mystery of Sagittarius A*’s missing wind, but the case isn’t quite closed. Direct evidence, such as measuring the velocity of an outflow of particles from the black hole, is still proving elusive. But with the answer so tantalizingly close, astronomers are still pushing to understand the mysterious heart of our galaxy.

    [ad_2]

    Ellyn Lapointe

    Source link

  • Breakthrough Image of Milky Way Black Hole Is Flawed, New Analysis Suggests

    Breakthrough Image of Milky Way Black Hole Is Flawed, New Analysis Suggests

    [ad_1]

    A team of researchers from Japan’s National Astronomical Observatory (NAOJ) is claiming that the groundbreaking image of the supermassive black hole at the center of our galaxy is not accurate.

    The original image of Sagittarius A* was constructed from data taken by the Event Horizon Telescope Collaboration, which revealed the picture to the public in May 2022. It showed our galaxy’s central black hole as an ominous black cloud surrounded by a ring of light—the hole’s accretion disk. In its paper, the recent team suggests that the the object is more likely to have an elongated disk. The team published its proposed black hole structure in the Monthly Notices of the Royal Astronomical Society.

    The 2022 image of the black hole depicts a four-million-solar-mass behemoth called Sagittarius A*. It is the first image of the object at our galaxy’s core and the Event Horizon Telescope (or EHT)’s second black hole image. The EHT’s first black hole image—the first-ever—depicted the black hole Messier 87 (M87), and published in 2019.

    Black holes are regions of spacetime with gravitational fields so intense that not even light can escape them at a certain distance. That distance is the black hole’s event horizon. There is a field of glowing superheated matter around the event horizon: the accretion disk. The team’s recent paper focused on the accretion disk of Sagittarius A*, which they claim has a different shape than previously thought.

    The EHT is a large radio observatory made up of a network of radio telescopes. EHT data reveal the black hole—an inherently invisible object, because light does not escape the event horizon—in its silhouette against a backdrop of its accretion disk.

    “We hypothesise that the ring image resulted from errors during EHT’s imaging analysis and that part of it was an artefact, rather than the actual astronomical structure,” said Miyoshi Makoto, an astronomer at the NAOJ and co-author of the paper, in a Royal Astronomical Society release.

    In its study, the team analyzed the same 2017 data on which the EHT Collaboration built its black hole image. But the team used a different method of analysis than the collaboration, indicating an elongated accretion disk compared to the doughnut structure seen in the 2022 image.

    A radio image of Sagittarius A* according to the recent team. Image: Miyoshi et al.

    The recent team contends that the black hole’s accretion disk is elongated. In other words, it has a different structure than the ring-like disk imaged in 2022. The M87 black hole also appears to have a ring-like shape in the EHT image, which a later team developed into a polarized image of the object, complete with the structure of its magnetic fields.

    In August, the EHT published a new method by which they improved the telescope’s resolution, hinting at sharper images of black holes in the near future. Should they follow through, future observations could clarify the actual structure of Sagittarius A*.

    Even further down the road, a space-based mission to improve the sharpness of EHT images may launch. The mission concept describes a $300 million investigation of black holes’ photon rings—is called the Event Horizon Explorer.

    Improving our understanding of the cosmos’ most extreme environments—the environments that foster black holes, neutron stars, and collisions of those two objects—will yield insights into the gravitational universe, as well as the core of our own galaxy.

    [ad_2]

    Isaac Schultz

    Source link