Scientists have unveiled the largest, most detailed map ever of the chaotic gas clouds at the center of our galaxy. The resulting image may take years to analyze, but promises to help unravel the mysteries of how the earliest stars lived and died soon after Big Bang.
The new observations, taken with the Atacama Large Millimeter/submillimeter Array (ALMA) radio telescope in Chile, cover 650 light-years of structures around the Milky Way’s central black holedeep in the constellation Sagittarius. This region is known as the Central Molecular Zone (CMZ) for its many clouds of dense molecular gas and is thought to mirror the compact and chaotic conditions of the earliest galaxies in the universe.
The entire image covers a parcel of sky roughly as wide as three full moons – the largest image ALMA has ever produced since operations began in 2013. This ultra-detailed view includes everything from giant clouds of supersonic gas to individual stars whipping around the galactic center and already shows some “rare and enigmatic“structures that defy explanation.
Zone of Chaos
Roll around the supermassive black hole Sagittarius A*The CMZ is a vast collection of colliding clouds, supersonic gas highways, and hyperactive stars that grow rapidly and die young. The region contains most of the dense gas in our galaxy — about 80%, according to Harvard and the Smithsonian Center for Astrophysics — and is the hottest, densest and most turbulent neighborhood in the Milky Way.
The turbulent flow of molecular gas supercharges star formation in parts of the CMZ, while other regions become confusingly empty. Scientists hope to understand how the large-scale processes that push matter through the CMZ control the evolution of small-scale objects, such as individual stars and gas clouds.
Enter the ACES – ALMA CMZ Exploration Survey, which brings together more than 160 researchers from 70 institutions around the world to study the mysterious CMZ. In a series of five papers Accepted for publication in the journal Monthly Notices of the Royal Astronomical Society, the ACES team shared the survey’s preliminary findings and how they could advance our understanding of the galactic center over the coming years.
The team noted that by studying the different wavelengths of light emitted by gas in the CMZ, the survey identified more than 70 types of molecules tumbling through the galactic center. These include both simple molecules, such as silicon monoxide, and more complex organic ones, such as ethanol and methanol, the researchers said.
By zooming in on specific areas of the image, the team was also able to see how specific processes — such as the eruption of shock waves released during massive gas cloud collisions — affected the heat, motion and chemical composition of different areas of the CMZ. All of this will eventually help scientists build a 3D map of the CMZ, revealing how different substructures are connected and how the large flow of matter leads to star formation and destruction.
“The CMZ hosts some of the most massive stars known in our galaxy, many of which live fast and die young, ending their lives in powerful supernova explosions and even hypernovae,” ACES team lead Steven Longmorea professor of astrophysics at Liverpool John Moores University, said in the statement.
Relics and curiosities
The preliminary findings also describe some unusual findings. One anomaly the team briefly noted is a structure called the Millimeter Ultra-Broad Line Object (MUBLO). The compact, dusty object appears only at millimeter wavelengths of light and is otherwise invisible to X-ray, infrared and radio telescopes.
Filled with fast-moving gas, MUBLO shows some characteristics similar to the active young stars expected to populate the galactic center — but so far the object’s characteristics do not match any other known structure in space, the team added.
Digging into anomalies like MUBLO and how they fit into the larger structure of the CMZ could open new doors to understanding the extreme environments of the ancient universe that are too far away to observe directly.
“By studying how stars are born in the CMZ, we can also get a clearer picture of how galaxies grew and evolved,” Longmore added. “We think the region shares many features 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 to include an additional image of CMZ.
