Five new superclouds of gas have been discovered just beyond the solar system. The work adds to two previously reported superclouds, including the Radcliffe Wave (illustrated), which wiggles above and below the plane of the fairly flat galaxy.
Ralf Konietzka, Alyssa Goodman, WorldWide Telescope
Astronomers have found a septet of superclouds lying just beyond the solar system. These giant strings of gas — five of which were previously unknown — sit nearly parallel to each other, and most of them undulate up and down in a wave pattern, researchers report in a paper submitted July 20 to arXiv.org.
“We finally [know] the interstellar cloud structure near us,” says independent astrophysicist Bruce Elmegreen, based in Katonah, N.Y. “It’s always been hard to see what is very local” to the solar system, because structures tend to blur together with most techniques.
Additionally, the superclouds, which may have formed from material shed by the Milky Way’s spiral arms, house most of the local stellar nurseries and probably gave rise to them. The gaseous behemoths could help researchers trace the hierarchy of structures that lead to star formation, says Elmegreen, a pioneer of supercloud research who was not involved in the study.
The find adds to the discovery of a nearby supercloud dubbed the Radcliffe Wave reported in 2020. It comes within 1,000 light-years of the solar system, and wiggles above and below the disk of the galaxy for thousands of light-years.
Building on that work, astrophysicist Lilly Kormann of the University of Vienna and colleagues examined a 3-D map of interstellar dust within some 50 million square light-years of the sun. The map was created using data from the Gaia spacecraft and published in 2024. Within that dust, “you see by eye some large-scale structures,” Kormann says. But she didn’t know exactly what they were.
Kormann turned the dust map into one showing the density of hydrogen, which fills up most of the space between stars. Searching for denser regions revealed 40 small clouds whose locations and orientations hinted that some were connected. After linking them up, the team identified seven long superclouds — including the Radcliffe Wave and a previously found one called the Split — lying nearly parallel to each other along the disk of the galaxy. All but the Split zigzag up and down, showing the shape is a common feature.
The seven superclouds range in length from about 3,000 light-years to 8,000 light-years and have masses roughly 800,000 to 3.5 million times that of the sun, making them our largest neighbors. They’re probably even bigger than that, Kormann says, since the calculations were confined to the map’s boundaries, and the huge strings of gas may extend beyond the edges.
Moreover, most of the known nearby stellar nurseries reside within the superclouds, particularly along their central axes. The arrangement suggests that superclouds are the “mothers” of smaller, denser clouds that collapse and produce stars, says astrophysicist João Alves of the University of Vienna.
Alves, Kormann and their colleagues are still figuring out why the superclouds weave up and down, how they spur star-birthing clouds and how they regulate their average densities — which closely match one another, despite considerable variation in the amount of material packed into any given stretch. “It’s just opening a lot of doors,” Alves says.
Elmegreen agrees. “This is just the beginning,” he says. The new catalog of superclouds and their features provides “tantalizing evidence that there’s a huge picture waiting to be discovered.”
