9,000-light-year-long monolithic structure discovered ‘right in front of our eyes’

8 Jan 2020

Illustration of the Radcliffe wave coloured red on the spiral arm of the Milky Way. Image: Alyssa Goodman/Harvard University

Astronomers have discovered an enormous gaseous structure in our own Milky Way made up of interconnected stellar nurseries.

A newly released map of the Milky Way has revealed an enormous wave structure that completely shocked the Harvard University team that discovered it. Publishing their findings to Nature, the researchers said the structure is the largest ever seen in our galaxy and is made up of interconnected stellar nurseries.

It’s estimated to be 9,000 light-years long and 400 light-years wide, with a wave-like shape that crests 500 light years above and below the mid-plane of the Milky Way’s disc. Many of the stellar nurseries included in this new 3D map were previously thought to form part of Gould’s Belt, a band of star-forming regions believed to be orientated around the sun in a ring.

In honour of Harvard’s Radcliffe Institute for Advanced Study, where the research collaboration called home, it has been dubbed the ‘Radcliffe wave’.

‘We couldn’t see it until now’

“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 Alyssa Goodman, a professor of applied astronomy at Harvard University.

“We were completely shocked when we first realised 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.”

One of the other researchers, João Alves, added that 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,” he said.

“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. What we do know is that our sun interacts with this structure. It passed by a festival of supernovae as it crossed Orion 13m years ago, and in another 13m years it will cross the structure again, sort of like we are ‘surfing the wave’.”

The map was created using precise star positioning data from ESA’s Gaia spacecraft combined with other measurements, revealing the unexpected wave in the galaxy’s spiral arm.

Colm Gorey was a senior journalist with Silicon Republic