As galaxy clusters form, they create clouds of hot electrons.

ECONOMIST: Cosmology

Gas clouds in the middle of the galaxy are, everyone agrees, partly ionised: radiation flying through has battered electrons off some of the atoms in the gas.

ECONOMIST: Here be serpents

Try as they might astronomers simply cannot see through these clouds to the centre of our Milky Way galaxy.

BBC: By BBC News Online Science Editor Dr David Whitehouse