Using data from ESA’s Gaia star-mapping spacecraft, a team of astronomers from Austria and the United States has discovered a wave-shaped arrangement of dense gas in our own neighborhood of the Milky Way.
The newly-discovered structure — named ‘Radcliffe Wave’ in honor of the Radcliffe Institute for Advanced Study — is about 9,000 light-years long and 400 light-years wide.
It contains about three million solar masses of gas and comprises the majority of nearby star-forming regions.
Some of these stellar nurseries were previously thought to form part of ‘Gould’s Belt,’ a band of star-forming regions believed to be oriented around the Sun in a ring.
“No astronomer expected that we live next to a giant, wave-like collection of gas — or that it forms the Local Arm of the Milky Way,” said Professor Alyssa Goodman, an astronomer at Harvard University, the Smithsonian Institution, and the Radcliffe Institute of Advanced Study.
“We were completely shocked when we first realized how long and straight the Radcliffe Wave is, looking down on it from above in 3D — but how sinusoidal it is when viewed from Earth.”
“The Wave’s very existence is forcing us to rethink our understanding of the Milky Way’s 3D structure.”
The research team combined Gaia data from with other measurements to construct a detailed, 3D map of interstellar matter in the Milky Way, and noticed the wave-shaped structure in the spiral arm closest to the Earth.
“Gould and Herschel both observed bright stars forming in an arc projected on the sky, so for a long time, people have been trying to figure out if these molecular clouds actually form a ring in 3D,” said Professor João Alves, an astrophysicist at the University of Vienna.
“Instead, what we’ve observed is the largest coherent gas structure we know of in the Galaxy, organized not in a ring but in a massive, undulating filament.”
“The Sun lies only 500 light-years from the Wave at its closest point. It’s been right in front of our eyes all the time, but we couldn’t see it until now.”
“We don’t know what causes this shape but it could be like a ripple in a pond, as if something extraordinarily massive landed in our Galaxy,” Professor Alves added.
“What we do know is that our Sun interacts with this structure. It passed by a festival of supernovae as it crossed Orion 13 million years ago, and in another 13 million years it will cross the structure again, sort of like we are ‘surfing the wave’,” he said.
A paper on the discovery was published in the journal Nature.