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. This reveals the temperature: the glowing gas isn't white-hot, but merely warm, around 2000–4000 °C. Not a flame, but a moist haze.
Previously, it was thought that the light from such "red dots" was born in a violent whirlpool of matter around a black hole. Now it's clear: the source is a dense cloud of water vapor, and its brightness is tens of times more modest. The mass estimates of central black holes dropped sharply: these are not supergiants, but moderate heavyweights.
The twist: under these conditions, water vapor leaves a unique light signature — a cosmic barcode readable across billions of light years. Thus, water, so distant from life as we know it, becomes a tool unveiling the true nature of distant worlds.
The trace of water in starlight is like a unique barcode from which we determine the temperature and density of the gas.