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Glossary · Telescopes & Instruments
Spectrograph
The instrument that splits light into its wavelengths, which is where the physics is.
A photograph tells you an object is there. A spectrum tells you what it is made of, how hot it is, how fast it is moving toward or away from you, whether it is rotating, and often how far away it is. Most of what astronomy knows came from spectrographs rather than cameras, and the biggest modern instruments are spectroscopic surveys — DESI takes five thousand spectra at once through robotically positioned fibres.
Where it has come up lately
NASA
AAS Nova
AAS Nova
NASA Science
Universe Today
Related terms
Lagrange point
Five places where two bodies' gravity lets a third sit still relative to both.
Adaptive optics
Bending a mirror hundreds of times a second to cancel out the atmosphere.
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.
Questions
What is Spectrograph?
The instrument that splits light into its wavelengths, which is where the physics is.
Why does it matter?
A spectrum tells you what it is made of, how hot it is, how fast it is moving toward or away from you, whether it is rotating, and often how far away it is. Most of what astronomy knows came from spectrographs rather than cameras, and the biggest modern instruments are spectroscopic surveys — DESI takes five thousand spectra at once through robotically positioned fibres.