Technosignature Spectroscopy: Visualisation · Signals from the Periphery

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THE TRANSIT

World

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Transit depth

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Selected gas

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TECHNOSIGNATURE SPECTROSCOPY
Reading another world's air, and what it can't tell you
a star, a planet, a hair of atmosphere, and a noise budget
JWST reads CO₂ on a hot Jupiter at 26σ, from one transit
an Earth twin at an M dwarf prints ~15 ppm per scale height
that star's own spots print 134–376 ppm, and never average down
pick an air · pick a telescope · read the verdict

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Evidence

fact ⇄ what kind of claim · live

The geometry: depth = (R_p/R_*)², signal = 2R_p·nH/R_*²

arithmetic on published radii, masses and temperatures

MEASURED

The cross-section ladder: halocarbons ~10⁻¹⁸ cm², O₂ at 7×10⁻²⁶

solved from the known effective altitudes of these bands in Earth's own limb

MODELLED

WASP-39b: CO₂ at 4.3 µm, 26σ, one transit, ≈1,300 ppm

JWST ERS 2022 · the one measurement this bench is calibrated against

MEASURED

TRAPPIST-1e's four real visits: 134–376 ppm of stellar contamination

unocculted spots and faculae · astrophysical, so it never averages down

MEASURED

Galileo, 1990: O₂ at 0.19, CH₄ at 3 ppm, disequilibrium ~10¹⁴⁰

the chemistry said life · only the radio said technology

MEASURED

K2-18b's DMS did not survive reanalysis; its methane did

1 binning choice in 8 recovered it · ethane fits the same data

REPORTED

CF₄ has a natural floor: 34 ppt from lithospheric degassing

measured in ~1300-year-old ice · "no natural source" is false for it

REPORTED

Whether a detection is a biosphere, a civilisation or a rock is a reading

the bench computes the budget; the file stays open

READING

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The world

The atmosphere

The gases · click to select, drag to set

CF₄ TECHNOSIGNATURE

Abundance—

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The telescope

Transits co-added15

Only about 17 TRAPPIST-1e transits are observable per JWST year, against the 60 that occur. The awarded campaign is 15.

Layers

The star's own spotsthe term that never averages down

Exaggerate the annulusor watch it vanish

Planet movingtransit view

Error barswhat a telescope records

Per-gas contributionswho owns which band

Band markersthe selected gas

Signal-to-noise ladderspectrum view

Labels

Readout · live

Scale height

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One scale height

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Bare transit depth

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Selected gas band

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Its feature

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Noise per bin

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Transits to 5σ

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What is measured vs modelled here

Measured: every stellar and planetary parameter, the geometry that follows from them, the JWST detections quoted in the file, the 1990 Galileo retrievals, and the stellar contamination amplitudes fitted to the four real TRAPPIST-1e visits. Reported: the technosignature proposals, the K2-18b claim and each of its reanalyses, CF₄'s natural background, and the published transit counts. Modelled: the cross-section ladder, every spectrum this bench draws, and every signal-to-noise and transit-count figure it prints. Reading: whether a completed chain of inference amounts to a claim about life.

The model, in full

Transmission spectroscopy in the standard analytic form. The scale height is H = kT/µm_ug. The slant path through the limb is long, √(2πR_pH), so the altitude at which it goes optically thick moves logarithmically with cross-section: z = H·ln(1 + σ/σ_ref), capped at ten scale heights and truncated from below by any cloud deck. The depth is then (R_p+z)²/R_*². The cross-sections are not asserted: they are solved from the separately known effective altitudes of these same bands in Earth's own limb. The single fitted quantity in the entire model is WASP-39b's cloud deck, set against its measured 4.3 µm CO₂ feature. Everything else is a consequence, which is why an Earth twin around the Sun comes out at sub-ppm and WASP-39b's bare disc at 2.12% against a published 2.13%.

Where this drawing takes liberties

The atmospheric annulus is drawn far thicker than it is, unless you switch that off. The star's spots are drawn at a size you can see. The spectrum is sampled at a few hundred points rather than line by line, so individual rovibrational lines are smooth bands here. The scatter on the plotted points is deterministic rather than random, so that screenshots are reproducible. The geometry, the published parameters, the band centres and every quotation take no liberties.

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the geometry the whole science lives in · click the star, the limb, the light curve