December 1, 2023
The Gaia satellite discovers fossil spiral arms in the Milky Way

The Gaia satellite discovers fossil spiral arms in the Milky Way

international team of Astronomy scientists Led by researcher Chervin Laporte, from the University of Barcelona’s Institute of Cosmology (ICCUB-IEEC), it used data from Gaia . satellite To create a new map of the outer disk of the Milky Way. The newly discovered structures were discovered by the study published in Monthly Notices of the Royal Astronomical Society: Letters, including evidence of fossil spiral arms in our galaxy.

Map of the Milky Way based on data from the Gaia satellite. Regions with high movement are shown in black and purple, while areas with relatively low movement are shown in yellow. A number of extensive filamentous disc structures are evident in the midlevel. The map also shows the Magellanic Clouds and their connecting star bridge on the left, while the dwarf galaxy Sagittarius, which is currently being absorbed, can be seen on the right. Credit: Chervin Laporte (ICCUB-IEEC)

By analyzing Gaia motion data, available as of December 2020, the team was able to identify coherent structures and assemble a map, which revealed the presence of many previously unknown spinning filaments at the edge of the disk. In addition, astronomers were also able to obtain a clearer overview of previously known structures.

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There are two explanations for the fossil filaments discovered in the Milky Way.

According to the site Phys, Numerical simulations indicate that such filamentous structures form in the outer disk from interactions with previous satellites, but the amount of infrastructure revealed by the map was not expected, and the remaining mystery: What could these structures be?

One possibility is that it was the remnants of the branches of the Milky Way’s disk that were stirred several times at different times space galaxies.

Currently, the Milky Way is surrounded by something like 50 galaxies belonging to these galaxies and has already “swallowed” many other galaxies. The dwarf galaxy Sagittarius is currently thought to be bothering her, but in the distant past she interacted with another intruder, Shaggy Gaia, who spread her wreckage around the predator.

In a previous study, the same team of researchers showed that one of the filaments in the outer disk, the Anticenter Current, contains stars more than 8 billion years old. This makes it too big to be triggered solely by recent arc activities, indicating the influence of the Shaggy of Gaia.

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Another possibility is that all of these structures are not truly true fossil arms, but instead form edges of large-scale vertical deformations in the disk of the Milky Way. “We think the disks respond to the effects of the satellites creating vertical waves that propagate like ripples in a lake,” says Laporte.

Future research may clarify the nature of these structures

To try to distinguish between the two interpretations, the team has now secured a follow-up program using the William Herschel Telescope, in Canary Islands, in order to study the characteristics of star clusters in each infrastructure. Future research will help clarify the nature and origin of these delicate celestial structures.

“This region of the Milky Way has remained unexplored due to intermediate dust that strongly obscures most of the galaxy’s middle plane,” LaPorte explained. “Although dust affects the star’s luminosity, its motion remains unchanged. We were certainly very excited to see that motion data from the Gaia satellite helped us discover these filament structures.”

According to him, the challenge now remains to “discover what exactly these objects are, how they appeared, why in such great numbers, and what they can tell us about the Milky Way, its formation and evolution.”

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