Stellar streams are long, ribbon-like groups of stars that orbit around a galaxy such as our Milky Way. These groups of stars all move together in long, slender lines that form glittering arcs around a galaxy, sometimes containing total masses millions of times the mass of the sun.
The streams are easily disrupted by gravitational effects, so they can show the fingerprints of dark matter by pointing to where its gravity has disturbed the stream. Scientists know that dark matter exists surrounding galaxies like the Milky Way in a structure called a halo, which contains clumps of dark matter. These clumps create gaps in the stellar streams which will be detectable by Rubin.
“Stellar streams are like strings of pearls, whose stars trace the path of the system’s orbit and have a shared history,” said Jaclyn Jensen of the University of Victoria who will use Rubin data for her research. “Using properties of these stars, we can determine information about their origins and what kind of interactions the stream may have experienced. If we find a pearl necklace with a few scattered pearls nearby, we can deduce that something may have come along and broken the string.”
It has been difficult for astronomers to study these stellar streams before because there are so many other stars in the Milky Way that it’s tough to spot which particular stars are part of a stream. So researchers will look for clues like the motion of certain stars to see whether they are moving together as part of a stream and will use Rubin’s ultraviolet capabilities to help identify the particular stars they are looking for.
