Milky Way is Warped

[ilan]

Our Milky Way is Warped
Deborah Byrd in SPACE | February 5, 2019

A team of astronomers has produced a 3D map of our galaxy, the 1st accurate one, they say. It reveals our galaxy’s true shape as warped and twisted.

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Our Milky Way isn’t the only warped galaxy. This galaxy – labeled ESO 510-G13 – is an edge-on warped spiral galaxy. Similar to the Milky Way it has a pronounced warp in its gaseous disk and a less pronounced warp in its disk of stars. Image via NASA/Space Telescope Science Institute.​

We think of spiral galaxies as being flat. You often hear the disk of our galaxy described as “flat as a pancake.” The large spiral galaxy next door – the Andromeda galaxy – looks flat through a telescope. But nature can be intricate, and, this week (February 4, 2019), astronomers made a surprising announcement. They said our home galaxy, the Milky Way, isn’t flat. Instead it’s warped and twisted.

Astronomers from Macquarie University and the Chinese Academy of Sciences used 1,339 classical Cepheid variable stars for this study. They are stars that brighten and dim in a way that changes according to the stars’ true luminosities. Thus these stars have been used as classic distance indicators. The astronomers used data on these stars from the Wide-field Infrared Survey Explorer (WISE). The work led them to create a 3D map of what they said is the “real” shape of our Milky Way. A paper describing this study was published February 4 in the peer-reviewed journal Nature Astronomy. The astronomers’ statement said:

They found the Milky Way’s disk of stars becomes increasingly ‘warped’ and twisted the further away the stars are from the galaxy’s center.​

Astronomers don’t like to think of our Milky Way as being in any way “special.” But – from what’s known today – its twisted shape does give it a specialness, although not a uniqueness. Astronomers have observed a dozen other galaxies that showed similarly twisted spiral patterns in their outer regions.

So our Milky Way’s twists are rare, but not unobserved elsewhere in the universe.
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It's gravity at play. The inner material (star disk) is more closely bound by gravity than the outer, gaseous disk. - ilan