Broken "stellar streams" may point to the Milky Way's undiscovered dark matter.

 

The Milky Way's dark matter may be found in shattered "stellar streamers."
pixabay.com


The spooky streams may tell which galaxies the Milky Way has devoured over time.


The Milky Way's halo is surrounded by vast rivers of stars, each cutting against the stream of our galaxy's halo. Researchers have discovered that a new type of star stream, known as a stellar stream, has an unusual orbit that may hold the key to finding our galaxy's hidden reservoirs of dark matter.


Two telescopes were used to gather data on the orbits, velocities, and compositions of 12 Milky Way star streams, which were then submitted for publication in the Astrophysical Journal and are now freely available on the preprint database arXiv.org.


Smaller star clusters have collided with the Milky Way in the past, causing our galaxy's gravity to drag and warp its smaller neighbours, resulting in the stellar streams we see today. These warped and tangled strands of matter orbit our galaxy's outer edges.


The researchers employed computer models to unravel the tangled strands of these elongated streams and discover their source. Six of the streams came from neighbouring dwarf galaxies (small galaxies containing up to several billion stars). In contrast, the other six originated from globular clusters, according to the team's analysis of the speed and composition of the stars in each stream (much smaller gravitational-bound bodies that contain up to a few thousand stars).


"This study gives us a snapshot of the Milky Way's eating patterns, such as what kinds of smaller star systems it 'eats,'" lead study author Ting Li, a professor of astronomy and astrophysics at the University of Toronto, said in a statement.


However, the study uncovered more than that. The researchers discovered that these 12-star streams were moving in ways that the Milky Way's gravity alone could not explain. The orbits of the streams appear to be controlled by non-luminous clumps of dark matter, which scientists believe accounts for around 85% of the universe's stuff.


According to University of Sydney co-author Geraint Lewis in a press release, a Christmas tree comes to mind. "In the dark, we only see the Christmas lights, but not the tree they are around. On the other hand, the shape of the lights exposes the tree's shape. Astronomers have found dark matter in stellar streams because the orbits of the stars show its presence."


More than 60-star streams have been spotted moving across the Milky Way, but researchers have never mapped this many of them at once. The distribution of dark matter in the Milky Way can be studied more clearly by tracking the passage of many streams simultaneously.


Researchers are hoping that this study, part of the Southern Stellar Streams Spectroscopic Survey (S5) programme, may lead to discoveries that help reveal the dark matter that underpins our galaxy.




Reference : https://www.livescience.com/stellar-streams-reveal-dark-matter-milky-way

Image source : https://pixabay.com/id/photos/bima-sakti-bimasakti-galaksi-kosmos-6209352/

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