The solar wind, a stream of charged particles from the Sun, slams into the tenuous gas that fills the space between the stars. The collision produces a faint X-ray glow. For astronomers, this is like fog in front of headlights: it obscures distant objects. The eROSITA telescope aboard the SRG space observatory scanned the entire sky four times, gathering data free from the interference of Earth's atmosphere. Scientists calculated the contribution of this glow and subtracted it from the overall picture.

The result is a map of the diffuse X-ray sky in the western part of the Galaxy — now without the extra background. But the real surprise is this: it turns out that this glow can be used to track how interstellar matter flows through the Solar System. Just as the haze from headlights reveals the direction of the wind on the road.