Hirofumi Noda

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.

In December 2024, quasar PG 1211+143 found itself in the crosshairs of two X-ray observatories at once: the spectrometers on XRISM and XMM-Newton observed it simultaneously. A quasar is the extremely bright core of a distant galaxy, where a supermassive black hole is accreting surrounding gas.

An X-ray beam is a stream of tiny packets of energy, photons. Ordinary detectors count them but don't distinguish shades: two photons with close energies look the same to them. The new device works like a sensitive thermometer: it catches each photon and measures how much it warms a thin film. From the warming, you can tell exactly how much energy the photon brought.

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.

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.

295 000 meters per second. Not even particles in solar coronal ejecta move that fast. But at the center of the galaxy cluster H1821+643, hot gas does exactly that. The quasar at its heart takes a breath, and its breath stirs everything around for 60 thousand light-years.