Scientists have released the largest and most detailed map yet of the chaotic gas cloud at the center of our galaxy. Analysis of the resulting images could take years, but they are expected to help solve the mystery of how early stars lived and died shortly after the Big Bang.
The new observations, taken with the Atacama Large Millimeter/Submillimeter Array (ALMA) radio telescope in Chile, cover 650 light-years worth of structure surrounding the Milky Way’s central black hole deep in the constellation Sagittarius. This region is known as the central molecular zone (CMZ) because of its large number of dense clouds of molecular gas, and is thought to closely reflect the dense and chaotic state of the oldest galaxies in the universe.
The complete image covers a portion of the sky the size of three full moons and is the largest image ever created by ALMA since it began operations in 2013. The ultra-detailed images include everything from giant clouds of supersonic gas to individual stars hopping around the galaxy’s center, and have already revealed some “rare and mysterious” structures that have no explanation.
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zone of chaos
The CMZ that snakes around the supermassive black hole Sagittarius A* is a vast collection of colliding clouds, supersonic gas highways, and hyperactive stars that grow rapidly and die young. This region contains most of the galaxy’s dense gas (about 80%, according to Harvard University and the Smithsonian Center for Astrophysics) and is the hottest, densest, and most turbulent region of the Milky Way.
Turbulent flows of molecular gas accelerate star formation in parts of the CMZ, while leaving other regions perplexingly empty. Scientists want to understand how the large-scale processes that push material into the CMZ control the evolution of small-scale objects such as individual stars and gas clouds.
Participate in ACES (ALMA CMZ Exploration Survey). The study brings together more than 160 scientists from 70 institutions around the world to study the mysterious CMZ. In a series of five papers accepted for publication in the Royal Astronomical Society’s monthly journal Monthly Notices, the ACES team shared preliminary findings from the study and how they could advance our understanding of the galactic center in the coming years.
By studying the different wavelengths of light emitted by gas within the CMZ, the researchers noted that they identified more than 70 types of molecules rolling around the center of the galaxy. These include both simple molecules like silicon monoxide and more complex organic molecules like ethanol and methanol, the researchers said.
By zooming in on specific regions of the image, the researchers were also able to see how specific processes, such as the eruption of shock waves released during collisions of large gas clouds, affect the thermal, kinetic, and chemical composition of different regions within the CMZ. All this will ultimately help scientists build a 3D map of the CMZ, revealing how the various substructures are interconnected and how large-scale material flows lead to star formation and destruction.
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“The CMZ is home to some of the most massive stars known in our galaxy, many of which live early and die young, ending their lives in powerful supernovae or even supernova explosions,” ACES team leader Professor Stephen Longmore, professor of astrophysics at Liverpool John Moores University, said in a statement.
relics and rarities
Preliminary findings also describe some unusual findings. One of the anomalies that the research team briefly noted was a structure called a millimeter-wave ultra-broad line object (MUBLO). This compact, dusty object appears only in millimeter-wavelength light and is otherwise invisible to X-ray, infrared, or radio telescopes.
Filled with fast-moving gas, Mburo exhibits some characteristics similar to the active young stars expected to populate galactic centers, but so far the object’s characteristics do not match any other known structures in the universe, the researchers added.
A closer look at anomalous phenomena like MUBLO and how they fit into the large-scale structure of the CMZ could open new doors to understanding the extreme environments of the ancient universe that are too distant to be directly observed.
“Studying how stars are born in the CMZ also gives us a clearer picture of how galaxies grow and evolve,” Longmore added. “We think this region shares many characteristics with galaxies in the early universe, where stars formed in chaotic, extreme environments.”
Editor’s note: This article was updated on February 25 at 10:30 a.m. to include additional images from CMZ.
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