A team of astronomers from Macquairie University (Australia) and the Chinese Academy of Sciences have used 1,339 stars to map the galaxy in which we live in three dimensions. Now we have a more accurate map of what our galaxy looks like from the outside. And it is not how we imagined.
The shape of the Milky Way, usually depicted as a flat spiral, may actually be more like a crooked and misshapen disk. According to the new study published in the journal Nature Astronomy, analysis of the distances of more than a thousand stars has resulted in a map that reveals a disk of inclined and uneven material different from our standard image of the Milky Way.
Pulsating star mapping
The 1,339 stars are all Cepheid variable stars, a type of pulsating star whose intrinsic brightness depends on how long it takes to vary from bright to dark and vice versa, that is, they emit regular pulsations, which are observed as changes in their brightness. Combined with the observed brightness of a Cepheid, its pulsation period can be used to obtain a highly reliable distance. Normally, it is difficult to tell if a star is really bright or close, dark or very far away. Since the period of a Cepheid tells astronomers how bright the star really is, by measuring how bright it appears, astronomers can draw a very accurate distance map.
Cepheids are young stars that are four to 20 times the mass of our Sun and can be up to 100,000 times brighter.
The astronomers looked at the WISE survey data on infrared stars and found that it contained a large sample of Cepheids. By measuring their distances and then plotting those stars in 3D, the researchers produced a new map of the Milky Way, one that shows a different spin, as it confirms a warped spiral pattern and its cause: the twisting that causes the huge inner disk to spin. of stars in our galaxy.
Astronomers have known for decades that the disk of gas in the Milky Way is warped. But the gas also extends nearly twice as far as stars in the visible disk and ignites, stretching higher and lower at the edges than the flat disk of stars. So the stars don’t necessarily follow the shape of the gas. It was necessary to find precise distances to the Cepheid stars to clarify the star map. The new data also adds a literal twist to the story, the twisting of the inner disk of stars. “Torsion is new,” says astronomer and study co-author Richard DeGrijs of Macquarie University in Australia. “It has been seen in a dozen galaxies before, but not in ours.”
“Combining our results with these other observations, we concluded that the deformed spiral pattern of the Milky Way is probably caused by rotational forcing, of the massive inner disk,” comments LIU Chao, principal investigator and co-author of the work.
“This new morphology provides an updated map crucial for studies of the stellar motions of our galaxy and the origins of the Milky Way disk, ” says Deng Licai, NAOC principal investigator and co-author of the paper.
While the study focused on making the galactic map rather than explaining it, the authors hypothesize that as the Milky Way’s inner disk of stars rotates, it also drags the outer disk, distorting the flat spiral.
Referencia: An intuitive 3D map of the Galactic warp’s precession traced by classical Cepheids, Nature Astronomy (2019). DOI: 10.1038/s41550-018-0686-7 , https://www.nature.com/articles/s41550-018-0686-7
This would be the real appearance of our galaxy seen from the outside:
