Understanding these stellar streams is very important for astronomers. In addition to revealing the dark matter that keeps stars in orbit, they tell us about the Milky Way’s formation history, revealing that the Milky Way has grown steadily over billions of years by smashing and consuming smaller star systems.

“We see these streams being disrupted by the Milky Way’s gravity and eventually becoming part of the Milky Way. This study gives us a snapshot of the Milky Way’s feeding habits, such as which smaller star systems it ‘eats’. The galaxy is getting older and it is getting fatter,” said Ting Li, a professor at the University of Toronto and lead author of the paper.

Prof Li and her international team of collaborators have launched a dedicated project – the Southern Stellar Stream Spectroscopic Survey (S5) – to measure the properties of stellar streams: the torn remnants of nearby small galaxies and star clusters torn apart by ourselves the Milky Way.

Li and her team were the first scientists to study such a rich collection of stellar streams, using Australia’s 4-meter optical telescope, the Anglo-Australian Telescope (AAT), to measure the velocities of stars. Li and her team used the Doppler shift of light — the same property that radar guns use to catch speeding drivers — to find out how fast individual stars are moving.

Unlike previous studies that focused on just one stream at a time, “S5 aims to measure as many streams as possible, and we can do this very efficiently using the unique capabilities of the AAT,” commented co-author Professor Daniel Zucker from Macquarie University .

Complete News Source : Sciencedaily