Andromeda galaxy has a humongous halo of gas – BBC Focus Magazine

Astronomers using the Hubble Space Telescope have mapped the enormous halo of gas surrounding the Andromeda galaxy the closest large galaxy to our Milky Way.
The map the most detailed of its kind shows that the halo of plasma (electrically charged gas) surrounding this spiral galaxy extends about 1.3 million light-years towards the Milky Way (about half of the distance), and as much as 2 million light-years in some directions.
The halo is invisible, but the researchers say that if it could be …

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