New data shows that the vast majority of our galaxy's mass is dark matter.
This stellar stream has been hiding in plain sight.
A new 3D map shows that our galaxy isn't nearly as tidy as we thought.
"We should not fear the supermassive black hole."
The collision "could knock us out of the Milky Way."
It's both massive and extremely diffuse.
There may be more of these lone wanderers than stars in the galaxy.
Eleven stellar streams have been identified, largely in the Milky Way's halo.
It accounts for 85 percent of all matter — yet we've never directly observed it.
This study transforms our understanding of how galaxies formed from the Big Bang.
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