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“No First” in the Milky Way: Our galactic neighborhood is shaking

“No First” in the Milky Way: Our galactic neighborhood is shaking

A few years ago, researchers from Vienna and the United States were able to decipher the 3D structure of our galactic neighborhood. Accordingly, the connected gas clouds near the Solar System are not, as has long been assumed, a ring-shaped belt around the Solar System, but rather a wave-shaped structure in the local arm of the Milky Way. Now they report in Nature that this structure, called a Radcliffe wave, also moves like a wave.

In the mid-nineteenth century, the British astronomer John Herschel and his American colleague Benjamin Gould discovered a supposed ring of bright stars that was not at the level of the Milky Way Galaxy, but was slightly inclined to it. This structure, called the Gould Belt, is a widespread collection of gas clouds containing young stars and star-forming regions.

Four years ago, while evaluating data from the European Gaia space telescope to create a detailed 3D map of the interstellar matter in the Milky Way, astronomers from the Universities of Vienna and Harvard stumbled upon a massive structure in the immediate vicinity of the Milky Way. Solar System. Because of its wave shape, they named the structure, which is about 9,000 light-years long and about 400 light-years wide, a “Radcliffe wave.” This extends up to 500 light-years above and below the central plane of the galactic disk and includes several star-forming regions previously assigned to the “Gouldian Belt.”

So close, but invisible

“The Sun is only 500 light-years away from its wavelength,” explained João Alves of the Institute of Astrophysics at the University of Vienna, who participated in the study. “It was directly in front of us all the time, but we could not see it.” He and colleagues at Harvard University published the results in the journal Nature. Now the research team has used new data from Gaia to decipher the structure's 3D movement.

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To do this, they examined the motion of young stars recently born from gas clouds along the Radcliffe wave. It turns out that the entire Radcliffe wave “moves like a traveling wave,” Alves said in a broadcast from the University of Vienna. The astronomer compares this movement to the wave of the “La Ola” stadium, where spectators imitate a wave moving across the sports arena by standing briefly one after the other, raising their arms and sitting down again.

Now that scientists understand how the Radcliffe wave works physically, “it can serve as our laboratory in space and help us gain more insights,” Alves emphasized. According to preliminary results, the type of wave oscillation indicates “the absence of a significant amount of dark matter in our galactic neighborhood.”

The researchers also showed that the structure is drifting radially away from the center of the galaxy. This again suggests that the star clusters in which the star explosion occurred (supernovae) could have originated in a Radcliffe wave, which formed a so-called “local bubble” about 15 million years ago, a dust-free bubble about 1,000 meters away. Light year. The size of the cavity around our sun, they write in their paper.

According to current data, the Radcliffe wave is likely to form the “backbone” of our upcoming spiral arm in the Milky Way, making up nearly half its length and about a fifth of its width. The researchers therefore wonder whether it is possible to use wave motion to infer that the spiral arms of galaxies oscillate in general. “Then galaxies will be more dynamic than previously assumed,” says Alves.

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