Infrared Observation
Studying heat and wavelengths our eyes cannot see.
Longer wavelengths scatter less off small dust grains, so sources hidden in visible light come through in the infrared. Cooler objects also radiate most of their energy there.
A detector sensitive beyond visible red records emission from objects that appear dark to the eye, and sees through dust that blocks shorter wavelengths.
- 01Objects radiate according to their temperature; cooler objects radiate mainly in the infrared.
- 02The wavelength where emission peaks constrains the temperature.
- 03Longer wavelengths scatter less off small dust grains, so obscured regions become visible.
- Observation
Infrared brightness recorded across a range of wavelengths.
- Measurement
How the emitted energy is distributed across those wavelengths.
- Physical model
Thermal emission and molecular absorption both leave signatures at infrared wavelengths.
- Inference
Temperature, and the presence of dust, ice and molecular species.
- +Temperature of a surface or atmosphere
- +Presence of dust, ices and many molecules
- +Structures hidden behind obscuring dust
- +Light from very distant sources shifted out of the visible range
What a method cannot settle matters as much as what it can. Each note below is tagged by how firm the statement is.
- OBSERVATION
Earth's atmosphere absorbs much of the infrared, and the telescope's own warmth adds background — which is why many infrared instruments are cooled and placed in space.
- INFERENCE
A temperature derived from a spectrum is a property of the emitting layer, not necessarily of the surface beneath it.
- HYPOTHESIS
Separating a planet's own thermal emission from reflected and stellar light depends on the model chosen for the system.
HD 189733 b
Infrared measurements taken as the planet passed behind and in front of its star were used to study its thermal emission rather than its reflected light.
open atlas record →