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Milky Way: Shape of Our Galaxy Revealed to be a warped and twisted "S"



EIt is about 25,000 light years away from the center of the Milky Way, so when it comes to our location in our Milky Way, we hang around in the suburbs. Our position in the Milky Way has made it very difficult for astronomers to count the number of stars and determine their shape. Until now it was accepted that our galaxy had the shape of other spiral galaxies: flat as a pancake. A new card reveals, however, that the truth is much more distorted.

In a study published Monday in Nature astronomy a team of Chinese scientists has announced that the Milky Way is actually formed in a "helical spiral pattern" that in its outer regions seems particularly S-like. While a distant view of the Milky Way looks like you are investigating a thin disc of stars, far away from its gravity-heavy inner planes are warped edges of hydrogen atoms, no longer limited to a flat surface.

The Milky Way has hundreds of billions of stars, a super-heavy black hole center and a huge mass of dark matter – it is a colossus held together by gravity "glue". The team behind the new newspaper added this picture by creating a Classic Cepheid database. These are young stars that are 20 times as massive as the sun and up to 100,000 times brighter. Because these stars are so bright, they served as localization points on a new three-dimensional map, in which the shape of the galaxy was calibrated.

Milky way card
Above: 3D distribution of the Cepheids on the warped disc of the Milky Way. Lower: precession of the line of buttons of the chain with Galactocentric ray.

"It is notoriously difficult to determine the distances of the sun to parts of the outer gas disk of the Milky Way without having a clear idea what that disk really looks like," said lead author Xiaodian Chen, Ph.D., Monday. "However, we recently published a new catalog with well-behaved variable stars, the classic Cepheïdie, for which distances can be determined as accurately as 3 to 5 percent."

From these data, using the reliable Cephei as reference points, Chen and his team extrapolated that the warped spiral of the outer ridges of the Milky Way is connected to rotational forces spinning out of the massive inner disc. This couple distorts the outer regions, giving the galaxy a progressively distorted spiral pattern – the further stars come from the middle, the more the disc of stars is distorted.

All this creates a rare phenomenon that astronomers have seen in other galaxies – but not ours. This research, senior researcher and co-author Licai Deng, Ph.D., says: "provides a crucial updated map for research into the movements of our galaxies and the origin of the galaxy's disc." The birth of the Milky Way was a billion-year process in which scientists are still working towards understanding, and that picture has just become a bit clearer

Abstract: The neutral hydrogen (H I) disc of the Milky Way is warped and expanded1,2. A lack of accurate H I-based distances has so far prevented the development of an accurate Galactic Disk model. Moreover, it is also unclear to what extent the stellar and gas disk morphologies of our Milky Way are mutually consistent. Classic Cepheids, primary distance indicators with distance accuracy of 3-5% (reference 3), offer a unique opportunity to develop an intuitive and accurate three-dimensional image. Here we set up a robust Galactic Disk model based on 1339 classic Cepheids. We provide strong evidence that the line of nodes of the chain is not oriented towards Galactic Center-Sun. Instead, an average angle of 17.5 ± 1 ° (formally) ± 3 ° is (systematically) included and shows a leading spiral pattern. Our Milky Way thus follows the line of Briggs for spiral galaxies4, suggesting that the origin of the warp is associated with torques forced by the massive inner disc5. The star-shaped disc traced by Cepheid follows the gas disk in terms of their amplitudes; the stellar disk extends to at least 20 kpc (see 6.7). This morphology provides a crucial, updated map for studies of the kinematics and archeology of the Galactic Disc.


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