WEBVTT

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JWST recorded this light when the universe was six hundred sixty-four million years old.

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The same patch of sky, band by band. Barely there in the blue. In the red, a point.

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Ten filters, laid out by wavelength.

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Each point is how much light arrives in one filter. Together they trace the object's color across the infrared.

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Faint blue light, then a sharp rise into the red. Between these two bands, the flux jumps nearly tenfold.

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A spectrum now, instead of ten samples of one. Every wavelength, in order.

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Hydrogen absorbs hard at one particular wavelength, but only when its electrons are already excited. That takes dense, warm gas.

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Stars can make a break, but the stellar templates compared here do not make one this large.

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Here is what the model puts inside.

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At the center, a black hole of about two million solar masses, swallowing gas.

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Around it, the last orbit gas can hold before it falls.

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Then a dense envelope of gas surrounds the center.

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Light escapes only at the photosphere, where the gas finally thins. Everything beneath it is inference.

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Consider a photon trying to escape through a layer of ionized gas.

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In this example, free electrons scatter it again and again. Forty-two optical depths imply about seventeen hundred scatterings.

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Across this model's skin: six hours in a straight line, about ten days by diffusion.

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Different routes spread out the arrival times. The delay depends on the layer's thickness and the assumed geometry.

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So how heavy is it? That turns on one number: the width of a hydrogen line.

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There it is, on the same spectrum. About three thousand kilometers a second.

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Line widths can trace motion. Read this one as orbits, and the estimate is two hundred million suns.

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Resonant scattering by hydrogen offers another way to broaden that line.

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Then it is around a million instead, running five times past its Eddington limit.

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Start with a seed, and grow it to the mass inferred at the time we observe it.

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The heavy example takes one and a half billion years. The universe here is only six hundred sixty-four million.

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The lighter example takes ninety-two million years. Both assume a seed mass, steady feeding, and a fixed efficiency.

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Change those assumptions and the times change. The clock constrains a growth history; it does not choose the model.

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If that is what this one is, it may be what a whole population is.

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Little red dots present several puzzles. This model offers a possible connection between their spectrum, size and weak X-rays.

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Extending the fitted blue spectrum into the red leaves an excess. Calling that excess an engine is the model.

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That is one possible reading.