Hiroshi Nakajima

About 25,000 light-years from Earth, in the constellation Sagittarius, a dense veil wraps around the neutron star GX 13+1. It scatters X-ray photons the way fog scatters streetlight, and for a long time it hid the source's true power from astronomers.

When a massive star runs out of fuel, it collapses and explodes, scattering the material from its interior across space. The remnant of such an explosion, Cassiopeia A, has long been known to astronomers for its lopsided appearance: bright clumps of material are scattered unevenly.

A giant cauldron of simmering soup stretches across millions of light-years. This is the atmosphere of the Perseus galaxy cluster — a cloud of scorching gas held together by gravity. Until recently, astronomers thought that in the center of this cauldron, the gas was calmly cooling, ready to condense into new stars.

Deep in the constellation Cygnus, two stars circle each other. One is a giant, the other a black hole. The giant continuously ejects a stream of gas into space — a stellar wind. When this wind falls under the black hole's X-rays, it lights up like a neon sign. Astronomers captured this light and split it into colors to learn what the wind is made of and how it moves.

The Perseus galaxy cluster is a giant metropolis of thousands of star islands, bathed in an invisible ocean of scorching gas. Like urban smog, this gas preserves traces of all the chemical factories that have operated in galaxies for billions of years: supernova explosions that scatter freshly forged atoms across the surroundings.