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Deep Field
29 September 2026 2518 stories tracked

Glossary · Telescopes & Instruments

Adaptive optics

Bending a mirror hundreds of times a second to cancel out the atmosphere.

The atmosphere is turbulent, and that turbulence smears a star into a blob several times larger than a good telescope's theoretical resolution. Adaptive optics measures the distortion — using a real star, or an artificial one made by firing a laser at the sodium layer 90 km up — and deforms a small mirror in the light path to cancel it, typically a thousand times a second. Done well it recovers most of what the telescope could do in space. It is the reason ground-based 8-metre telescopes can resolve exoplanets at all, and the reason the 39-metre ELT under construction in Chile is worth building.

Related terms

Lagrange point Five places where two bodies' gravity lets a third sit still relative to both. Interferometry Combining separate telescopes so they resolve detail like one enormous dish. First light The night a new telescope is pointed at the sky and actually works. Seeing How much the atmosphere is blurring the stars tonight, measured in arcseconds.

Questions

What is Adaptive optics?

Bending a mirror hundreds of times a second to cancel out the atmosphere.

Why does it matter?

Done well it recovers most of what the telescope could do in space. It is the reason ground-based 8-metre telescopes can resolve exoplanets at all, and the reason the 39-metre ELT under construction in Chile is worth building.

Written and computed by . Corrections and errors to hello@cantinalabs.dev.