Answer to Question #304329 in Astronomy | Astrophysics for Anuj S Sharma

Question

The electromagnetic spectrum contains various types of radiation with dierent properties. The

James Webb Space Telescope is not like an optical telescope at home and does not capture visible light; instead, it observes the sky in the infrared spectrum.

Explain what infrared radiation is and answer the following questions: How is infrared radiation

dierent from visible light? Why does the JWST observe infrared light, and what are the scientific advantages for astronomers?

Answer 1

Infrared radiation is a kind of electromagnetic radiation with wavelengths from approximately 700 nm to 1 mm, the energy of this radiation is smaller than the energy of the visible light. Human cannot see this radiation by eye, but human body emits in infrared.

Lots of celestial objects emit in infrared. Cold small stars emit large fraction of their radiation in infrared. Protoplanetary disks and protostars also emit in this wavelength range. Cold, dark molecular clouds of gas and dust also glow in infrared, so observations in infrared are very useful. Moreover, extinction in infrared is significantly smaller than in visible light, so in infrared it is possible to study objects in galactic disk and the central parts of our galaxy. Worth noting, the infrared radiation is absorbed by the water vapour in atmosphere of the Earth, so it is important to send infrared telescopes to near-Earth orbits and not to observe from the Earth surface.