The Milky Way is warped and twisted around, scientists discover

Breakthrough finally shows our galaxy is not flat or stable as expected

Artist's impression of the warped and twisted Milky Way disk (CHEN Xiaodian)

Our galaxy is twisted and warped, scientists have said after a shock discovery.

The Milky Way that surrounds us has long been presumed to be relatively stable and flat. But scientists have accurately mapped the galaxy for the first time, and found that it becomes increasingly warped and twisted towards the edges.

It has been notoriously difficult to see the shape of our own galaxy, even as we have mapped others in detail. We are stuck inside of it and it is difficult to see: scientists liken the experience of measuring the Milky Way to standing in your garden and trying to work out what shape your country is.

Now researchers have used 1339 stars to create a map that reveals the true shape of our galaxy. They found that the disc of stars twists up as it approaches the edges, far from the flat shape that scientists have seen in other galaxies.

"We usually think of spiral galaxies as being quite flat, like Andromeda which you can easily see through a telescope," says Professor Richard de Grijs, a co-author and astronomer from Macquarie University in Sydney, Australia.

If you were looking at our galaxy from the outside and at a distance, you would see a thin disc of stars that orbit around a central region, every few hundred million years. Hundreds of billions of stars and a whole host of dark matter stirs it all together as a gravitational meld.

But the further away from the inner regions of the Milky Way you are, the less the pull of gravity. At the outer disc, the hydrogen atoms that make up the Milky Way's gas disc are as a consequence warped into an S-like shape, and no longer pulled together in a thin plane.

For decades, scientists have seen indications that the hydrogen clouds in own galaxy might be strangely shaped. But the new research shows that the warped disc also includes young stars, and confirms that the warped spiral of the Milky Way comes from the torque produced as the massive inner disc of stars spins around.

"It is notoriously difficult to determine distances from the Sun to parts of the Milky Way's outer gas disc without having a clear idea of what that disc actually looks like," says Xiaodian Chen, lead author, from the Chinese Academy of Sciences in Beijing.

Astronomers have previously seen similar galaxies that have the strange warped and twisted shape at their edges, though it is a rare phenomenon. But it wasn't clear previously that our galaxy belonged to that strange set.