A huge mystery object has collided with the Milky Way, resulting in an enormous wave forming on the galactic plane.
Scientists have said the mystery object could potentially be a clump of dark matter, while the wave – known as the ‘Radcliffe wave’ – covers half the sky from Earth, making it difficult to see the whole structure.
The wave was discovered using data from the European Space Agency’s Gaia satellite, and had previously gone unnoticed because of its extreme size and our proximity to it.
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The wave, made up of interconnected stellar nurseries, is very close to the Milky Way. At its closest point, the Sun is just 500 light years from the wave, which runs directly behind our solar system as viewed from the heart of the galaxy.
Researchers led by João Alves, from the Department of Astrophysics at the University of Vienna and the Radcliffe Institute for Advanced Study at Harvard University, were initially trying to map Gould’s Belt, a large band of star-forming regions.
In doing so, they discovered Gould’s belt is ‘just a projection effect’ of a far larger structure, the Radcliffe wave. ‘As you can imagine, I was very surprised,’ Alves told Newsweek.
The researchers discovered that the Radcliffe wave was one enormous, long filament, stretching 9,000 light years in length and 400 in width. It was also found to go 500 light years above and below the mid-plane of the galactic disk in a wave-like shape.
Alves explained:
The reason why we didn’t realise the presence of this giant is that we didn’t have the exquisite distance measurements we have today with Gaia and, I think because we are so close to the structure it’s hard to see it.
Details of the discovery are published in the journal Nature, with researchers saying the wave’s amplitude appears to be decreasing over time. This suggests some sort of trigger, perhaps a collision between the disk of our Milky Way and a massive object – that scientists so far have not identified.
They believe it could be a clump of dark matter, as this would explain why we cannot find an obvious candidate for the collision. However, Alves admits this is just ‘speculation’ at the moment, adding: ‘Other scenarios are as plausible.’
The researcher said his team have ‘many ideas’ that they will be testing with future releases of Gaia data, but they don’t have a ‘favourite scenario’ at the moment.
The team now hopes to find similar structures in other parts of the Milky Way, and are trying to locate and measure the wave’s teenage stars, which should help them work out what could have caused the wave to form.
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A Broadcast Journalism Masters graduate who went on to achieve an NCTJ level 3 Diploma in Journalism, Lucy has done stints at ITV, BBC Inside Out and Key 103. While working as a journalist for UNILAD, Lucy has reported on breaking news stories while also writing features about mental health, cervical screening awareness, and Little Mix (who she is unapologetically obsessed with).