Milky Way is warped and twisted, not flat

Cristina Cross
February 7, 2019

The researchers gathered 2,330 Cepheid variables catalogued by an infrared telescope called the Wide-field Infrared Survey Explorer, and whittled down the list to 1,339 stars based on their distance, models of the Milky Way, and other factors.

Classical Cepheids are young stars that are some four to 20 times as massive as the sun and up to 100,000 times as bright.

The light of these short-lived stars changes regularly, in day- to month-long cycles.

An global team of astronomers has used 1,339 classical Cepheid stars - pulsating variable stars each up to 100,000 brighter than our Sun - to map the real shape of our Milky Way Galaxy.

Without accurate measures of the distance between the sun and stars in the Milky Way's outer regions, it's hard to determine the precise shape of the galaxy and its gas disk.

Our Milky Way galaxy's disk of stars is anything but stable and flat. Astronomers think the twisted nature of the outer disk is caused by rotational forcing generated by the dense inner regions of the Milky Way.

Chen Xiaodian, lead author of the study and a researcher at the National Astronomical Observatories of Chinese Academy of Sciences, said that accurate distances from the Sun to parts of the Milky Way's outer disc were key to knowing what that disc actually looked like.

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The Milky Way galaxy's new shape has a twist - exaggerated here for effect.

The Milky Way really is warped - like a bent old vinyl record, according to new research.

The same twisted spiral patterns have been seen before in more than a dozen other galaxies.

A team of astronomers from the Macquarie University in Australia and the Chinese Academy of Sciences have mapped out the Milky Way using 1,339 "standard stars".

Researchers from Macquarie University, Australia, and the Chinese Academy of Sciences made their findings after creating a new 3-D map of the Milky Way, which allowed them to better estimate its shape. Combined with a Cepheid's observed brightness, its pulsation period can be used to obtain a highly accurate distance.

From the 3D distribution map, researchers found that the new derived stellar disc is warped in a progressively twisted spiral pattern, with an S-shape. Their paper is published online today in Nature Astronomy.

From a great distance our galaxy would look like a thin diss of stars that orbit once every few hundred million years around its central region. But as you move toward the outermost reaches of the galaxy, the gravitational glue of the centre fades. Since hydrogen atoms in the far outer disk are no longer confined to a thin plane, they get warped. "Perhaps more importantly, in the Milky Way's outer regions, we found that the S-like stellar disk is warped in a progressively twisted spiral pattern".

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