Some 12 billion years ago, the Milky Way looked very different to the orderly spiral we see today. We think that our galaxy formed as multiple long, irregular filaments of gas and dust coalesced, all forming stars and wrapping together to spark the birth of our galaxy as we know it. It seems that Shaki and Shiva are two of these components – and future Gaia data releases may reveal more.

Khyati and Hans-Walter also built a dynamical map of other known components that have played a role in our galaxy’s formation and were discovered using Gaia data. These include Gaia-Sausage-Enceladus, LMS1/Wukong, Arjuna/Sequoia/I’itoi, and Pontus. These star groups all form part of the Milky Way’s complex family tree, something that Gaia has worked to build over the past decade.

“Revealing more about our galaxy’s infancy is one of Gaia’s goals, and it’s certainly achieving it,” says Timo Prusti, Project Scientist for Gaia at ESA. “We need to pinpoint the subtle yet crucial differences between stars in the Milky Way to understand how our galaxy formed and evolved. This requires incredibly precise data – and now, thanks to Gaia, we have that data. As we discover surprise parts of our galaxy like the Shiva and Shakti streams, we’re filling the gaps and painting a fuller picture of not only our current home, but our earliest cosmic history.”