Radcliffe wave oscillates, astronomers discover

Our Sun lies within 300 parsecs (about 1,000 light years) of a 2,700-parsec- (about 9,000-light-year-) long sinusoidal chain of dense gas clouds known as the Radcliffe wave. The wave-like shape of the structure was discovered using 3D dust mapping, but initial kinetic searches for oscillating motion were inconclusive. According to the new research, the Radcliffe wave oscillates through the plane of our Milky Way galaxy while also moving radially away from the galactic center.

A Radcliffe wave (yellow dot) next to our Sun inside a cartoon model of the Milky Way. The blue dots are clusters of baby stars. The white line is Konitzka's theoretical model and many others. It explains the current shape and movement of the wave. The magenta and green lines show how the wave will move in the future. Image credit: Ralf Konitzka / Alyssa Goodman / Universal Telescope.

„By using the motion of baby stars born in gas clouds in a Radcliffe wave, we can trace the motion of their birth gas to show that the Radcliffe wave is indeed moving,” said Ph.D. student at the Harvard & Smithsonian Center for Astrophysics.

In 2018, astronomers mapped the 3D positions of stellar nurseries in the Sun's galactic neighborhood.

By incorporating brand new data ESA's Gaia mission With a data-intensive '3D dust mapping' technique, they observed a pattern emerging, leading to the discovery of the Radcliffe wave in 2020.

„This is the largest coherent system we know of,” said Dr. Catherine Zucker, an astronomer at the Harvard & Smithsonian Center for Astrophysics.

“It's been there the whole time. We don't know about this because we haven't been able to make these high-resolution models of the distribution of gas clouds near the Sun in 3D.

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The 3D dust map clearly showed the presence of the Radcliffe wave, but no measurements were sufficient to see if the wave was moving.

But in 2022, using a new release of Gaia data, astronomers provided 3D motions for young star clusters in the Radcliffe wave.

With the positions and motions of the clusters in hand, they were able to determine that the entire Radcliffe wave was oscillating, moving as what physicists call a 'traveling wave'.

„The traveling wave is the same phenomenon we see in a sports arena, where people stand up and sit on the airwaves and make waves,” Konitska said.

„Similarly, the star clusters in the Radcliffe wave move up and down, creating a pattern that travels through our galactic backyard.”

„Just as fans in a stadium are pulled back to their seats by Earth's gravity, so Radcliffe is swayed by the gravity of the wandering Milky Way.”

No one yet knows what causes the Radcliffe wave or why it moves.

„Now we can go and test these different theories as to why the wave formed in the first place,” Dr Zucker said.

„Those theories range from massive stellar explosions called supernovae to extragalactic disturbances, such as a dwarf satellite colliding with our Milky Way,” Konitzka added.

„It turns out that we don't need significant dark matter to explain the motion we observe.”

„The gravity of ordinary matter alone is sufficient to drive the wave.”

In addition, the discovery of the oscillation raises new questions about the dominance of these waves in both the Milky Way and other galaxies.

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Since the Radcliffe wave appears as the backbone of a nearby spiral arm in the Milky Way, the tidal wave may indicate that the spiral arms of galaxies are normally oscillating, making galaxies more dynamic than previously thought.

„The question is, what displacement causes the oscillation we see?” said Professor Alyssa Goodman, an astronomer at the Harvard & Smithsonian Center for Astrophysics.

„And does it happen across the galaxy? In all galaxies? Does it ever happen? Does it happen all the time?

The Results appear in the magazine Nature.

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R. Konitska and many others. Radcliffe wave swings. Nature, published online February 20, 2024; doi: 10.1038/s41586-024-07127-3

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