Koji Mukai

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.

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.

Every five hours in the binary system IPHAS J190812.63+045728.1, one star completely hides the other. For 18 minutes, the white dwarf and its scorching disk vanish from sight, leaving only a modest red neighbor in the dark. This is a natural shutter that switches off the spotlight to reveal what usually hides in its glare.