Dark matter around the Milky Way betrayed by star currents

The stellar currents that surround the Milky Way reveal a story in which it literally devoured a few of its fellow travelers. But they also provide valuable clues about the nature and distribution of the dark matter that surrounds our Galaxy.

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[EN VIDÉO] Dark matter lurks in the Milky Way’s halo
Astronomers from Harvard University (USA) have drawn up a map of the outer halo of our Milky Way. The opportunity for them to deduce the presence of dark matter, this invisible substance supposed to constitute a large part of the mass of our Universe. Their simulation shows two areas of high density, in light blue. The smaller structure that appears on the map corresponds to the wake left by the passage in the region of the Large Magellanic Cloud, a satellite galaxy of ours. © NASA/JPL-Caltech/NSF/R. Injured/N. Garavito-Camargo and G. Besla

“Think about your Christmas tree», comments Geraint Lewis, researcher at the University of Sydney (Australia), in a statement from the university of chicago (United States). It’s still a little seasons . “In the night, you only see the lights, but they give you an indication of its shape. » And it is with the same state of mind that the researchers hope today to reveal the black matterthat surrounds the Milky Way . From the observation of orbits of a dozen stellar currents in the halo of our Galaxy.

The first information about the black matter that these star streams can bring to astronomerscomes from their speed . They were able to determine it using the telescopeAnglo-Australian from the observatory of Siding Spring (Australia). But that’s not all, since an analysis of the chemical composition of the stars that make up these currents also gives information on the nature of dark matter.

Twelve streams of stars under the eye of the telescope

And this is the first time that astronomers are interested not in a current of stars, but in “as many currents as possible”. That’s a dozen, for now. A work made possible in particular thanks to data from the european space mission Gaia . It provides very precise measurements of the positions and movements of the stars in question. What hope to identify new currents. And finally flush out the dark matter that surrounds our Galaxy.

This work will also help to understand how the Milky Way was born in an almost reliefless universe. By shredding and swallowing regularly star systemssmaller. “The most intriguing question about our ultimate origins”, according to Ting Li, a professor at the University of Toronto.

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