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Equation 3 · Part 1 · Comparing the Main Approaches to Planetary Science and Exploration

Symbol θ

θ≈1.22 λD.\theta \approx 1.22\,\frac{\lambda}{D}.
θ\theta

What this part means

θ is a part of this expression. Its role is fixed by the surrounding article and by the operations shown in the formula.

Its job in the formula

θ is a part of this expression. Its role is fixed by the surrounding article and by the operations shown in the formula.

The passage around this formula

…is approximately θ≈1.22 λD\theta \approx 1.22\,\frac{\lambda}{D}. This relation is why an exoplanet studied by transmission spectroscopy is a single point of light with no visible surface at all — the target subtends an angle far smaller than θ\theta for any existing telescope, so every observation is necessarily a disk-integrated average over the whole illuminated hemisphere. Even for solar-system bodies, where θ\theta is far less limiting because the object is millions rather than trillions of kilometres away, ground- and space-based…

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A variable is a named place for a value. Its letter is a local label: x can mean position in one formula and a data point in another.

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Sources cited in the article section

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