First accurate 3D map of the Milky Way shows the galaxy is warped

Feb. 5 (UPI) — Researchers in Australia and China have for the first time unveiled an accurate 3D map of the Milky Way galaxy. Their mapping efforts revealed the warped nature of the galaxy’s far outer disk.

Astronomers from from Macquarie University and the Chinese Academy of Sciences shared their map in the journal Nature Astronomy.

The gravitational pull of the Milky Way’s center keeps the swirl of stars inside its inner regions orbiting within a relatively flat, thin plane. But among the galaxy’s outer regions, the gravitational influence of the galactic core is relatively weak.

Without the strictures of strong gravity, the outer gas disk’s hydrogen atoms form an S-like, warped structure — a twist.

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

“However, we recently published a new catalogue of well-behaved variable stars known as classical Cepheids, for which distances as accurate as 3 to 5 per cent can be determined,” Xiaodian Chen, a researcher at the Chinese Academy of Sciences in Beijing, said in a news release.

The new stellar distance database allowed scientists to build a detailed 3D map of the Milky Way’s gas disk.

Cepheids are big and bright young stars. They live fast and die young. Classical Cepheids are 20 times more massive that the sun and as much as 100,000 times brighter. The energetic stars pulsate, and by messing the timing of the stellar pulses and the changes in brightness, scientists can accurately measure their distance from Earth and the sun.

“Somewhat to our surprise, we found that in 3D, our collection of 1339 Cepheid stars and the Milky Way’s gas disk follow each other closely,” said Richard de Grijs, professor at Macquarie University in Sydney. “This offers new insights into the formation of our home galaxy.”

“Perhaps more important, in the Milky Way’s outer regions, we found that the S-like stellar disk is warped in a progressively twisted spiral pattern,” de Grijs said.

Scientists have found similar warped shapes among the outer regions of other spiral galaxies. Astronomers think the twisted nature of the outer disk is caused by rotational forcing generated by the dense inner regions of the Milky Way.