For the past couple of weeks, we’ve brought you stories on streams of stars that point toward our galaxy’s past consumption of dwarf galaxies that got too close. As we mentioned, it’s the time of year when, for whatever reason, these stories tend to come out, and today, we have a story that brings together all these streams to shape one really cool result.

A team of researchers led by Ting Li at the University of Toronto has used the Anglo-Australian four-meter telescope to perform the Southern Stellar Stream Spectroscopic Survey — a survey to measure the chemistry and detailed motions of the stars in twelve different stellar streams, which in turn reveal the effects of dark matter. Geraint Lewis, a collaborator on the project, explains it this way: Think of a Christmas tree. On a dark night, we see the Christmas lights, but not the tree they are wrapped around. But the shape of the lights reveals the shape of the tree. It is the same with stellar streams – their orbits reveal the dark matter. 

This paper appears in The Astrophysical Journal, and according to the abstract: The velocity and metallicity dispersions show that half of the stream progenitors were disrupted dwarf galaxies (DGs), while the other half originated from disrupted globular clusters. 

By looking at the chemistry and motions of these streams, they also start to hint at how some streams and some not-destroyed objects in the galactic halo may be related to specific streams. This is an ongoing project, and we look forward to seeing more details published over time.

More Information

Lowell Observatory press release

University of Chicago press release

University of Toronto press release

“S5 : The Orbital and Chemical Properties of One Dozen Stellar Streams,” Ting S. Li et al., to be published in The Astrophysical Journal (preprint on arxiv.org)