Maxim Markevitch

The red dot in the James Webb Space Telescope image is the galaxy Bz5.3, whose light has traveled 12.5 billion years to reach us. It lies behind the Bullet Cluster, whose gravitational field acted as a lens and brightened it by a factor of 3.7.

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 Bullet Cluster is a cosmic collision site where two vast clouds of galaxies, gas, and invisible matter slammed into each other. When light from distant stars passes near such a cluster, gravity bends its path like a lens. Astronomers study these distortions to work out where the mass is hiding.

Every galaxy is wrapped in an invisible shell of hot gas, like steam rising from a pot of boiling water. This gas barely glows in X-rays, making it notoriously difficult to measure. Yet it holds the memory of stellar explosions and the galaxy's growth. The new method uses light from a galaxy's bright center.

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.

An orchestra of hundreds of galaxies performs a symphony in X-rays, but until recently we heard only a general hum. The Coma Cluster is about a thousand galaxies immersed in a cloud of scorching gas at a temperature of one hundred million degrees. This gas glows in X-rays, and its spectrum tells us how it moves.