Astronomers observe the oscillation of the Radcliffe wave

A few years ago, astronomers discovered one of the Milky Way’s greatest secrets: a huge chain of wave-shaped gaseous clouds in the backyard of our sun, giving rise to clusters of stars along the spiral arm of the galaxy we call home.

Naming this astonishing new structure Radcliffe Wave, in honor of Harvard’s Radcliffe Institute, where the ripple was originally discovered, the team now reports in Nature that Radcliffe’s wave not only looks like a wave, but also moves like one, oscillating in space-time much like “the wave” moving in a stadium full of fans.

Ralf Konietzka, lead author of the paper and a Ph.D. student at Harvard’s Kenneth C. Griffin Graduate School of Arts and Sciences, explains: “Using the movement of baby stars born in gas clouds along the Radcliffe Wave, we can trace the movement of their native gas to show that the Radcliffe wave is in fact, I wave. »

In 2018, when Professor João Alves of the University of Vienna was a member of the Harvard Radcliffe Institute, he worked with Catherine Zucker, a researcher at the Center for Astrophysics, then a doctoral student. student at Harvard and Alyssa Goodman, the Robert Wheeler Willson Professor of Applied Astronomy, to map the 3D positions of stellar nurseries in the galactic neighborhood of the sun.

By combining brand new data from the European Space Agency’s Gaia mission with the intensive 3D Dust Mapping technique — developed by Harvard Professor Doug Finkbeiner and his team — they noticed the emergence of a model that led to the discovery of the Radcliffe wave in 2020.

“It’s the largest coherent structure that we know of, and it’s really, really close to us,” said Zucker, who describes the collaboration’s work in a related Sky and Telescope article. “It’s always been there. We just didn’t know it, because we couldn’t build these high-resolution models of the distribution of gaseous clouds near the sun, in 3D.”

The 3D dust map from 2020 clearly showed that the Radcliffe Wave existed, but no measurements available at the time were good enough to see if the wave was moving. But in 2022, using a newer version of Gaia data, Alves’ group attributed 3D motions to young Radcliffe Wave star clusters.

With the positions and movements of the clusters in hand, Konietzka, Goodman, Zucker and their collaborators were able to determine that the entire Radcliffe wave does indeed undulate, moving like what physicists call a “traveling wave.”

A progressive wave is the same phenomenon we see in a sports stadium when people stand up and sit down in sequence to “do the wave.” Likewise, star clusters along the Radcliffe Wave move up and down, creating a pattern that runs across our galactic backyard.

Konietzka continued: “In the same way that fans in a stadium are pulled back to their seats by Earth’s gravity, the Radcliffe wave oscillates due to the gravity of the Milky Way.”

Understanding the behavior of this gargantuan 9,000 light-year structure in our galactic backyard, just 500 light-years from the sun at its closest point, allows researchers to now turn their attention to even more difficult questions. No one yet knows what caused the Radcliffe wave or why it moves the way it does.

“Now we can test all these different theories about why the wave formed in the first place,” Zucker said.

“These theories range from massive star explosions, called supernovae, to out-of-galaxy disturbances, such as a dwarf satellite galaxy colliding with our Milky Way,” Konietzka added.

THE Nature The paper also includes a calculation of the amount of dark matter that could contribute to the gravity responsible for the wave’s motion.

“It turns out that no significant dark matter is needed to explain the motion we observe,” Konietzka said. “The gravity of ordinary matter alone is enough to cause the wave to move.”

Furthermore, the discovery of the oscillation raises new questions about the preponderance of these waves both in the Milky Way and in other galaxies. Since the Radcliffe wave appears to form the backbone of the nearest spiral arm in the Milky Way, the undulation of the wave could imply that the spiral arms of galaxies oscillate in general, making the galaxies even more dynamic than previously thought.

“The question is: what caused the displacement giving rise to the unrest we are seeing?” Goodman said. “And does this happen everywhere in the galaxy? In all galaxies? Does it happen occasionally? Does it happen all the time?”