- Observations made by a small spacecraft called HaloSat have shown that the Milky Way galaxy is surrounded by a clumpy halo of hot gases that is continually being supplied with material ejected by birthing or dying stars.
- The heated gaseous halo around the Milky Way was the incubator for the Milky Way's formation some 13 billion years ago and could help solve a longstanding puzzle about where the missing matter of the universe might reside.
- Every galaxy has a circumgalactic medium, and these regions are crucial to understanding not only how galaxies formed and evolved but also how the universe progressed from a kernel of helium and hydrogen to a cosmological expanse teeming with stars, planets, comets, and all other sorts of celestial constituents.