Anna de Graaff

A distant red object usually means one thing: we're seeing a dust veil over a scorching disk falling into a black hole. But when the James Webb split its light into shades, a shadow appeared inside — just like steam from boiling water intercepts rays.

If you turn on a lamp in a room, it illuminates the walls. But if you place the same lamp in a vast hall, the light barely reaches the corners. Similarly, radiation from young stars affects gas in a galaxy: it knocks electrons out of hydrogen atoms, making the gas glow.

When JWST peered into the young universe at redshifts of 6–10, it revealed a scattering of mysterious 'little red dots' (LRDs). These objects combined features of galaxies and active nuclei, but their spectra refused to fit into familiar patterns.

The JWST spectrograph caught a barely perceptible dip in the spectrum of a distant galaxy — two lines, like shadows cast by cold gas. These are the sodium lines, the very yellow light of streetlamps. Here, at the edge of the visible Universe, they betray the slow exhalation of a galaxy returning matter to space.