Answer to Question #305465 in Astronomy | Astrophysics for J17

Question

The electromagnetic spectrum contains various types of radiation with different 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 different from visible light? Why does the JWST observe infrared light, and what are the scientific advantages for astronomers?

Answer 1

Infrared radiation (IR), also known simply as infrared, is a type of electromagnetic radiation with wavelengths varying from 700 nanometers (nm) to 1 millimeter. Infrared light have a longer wavelength than visible light waves but a shorter wavelength than radio waves. Infrared frequencies, which range between 300 Ghz and 400 THz, are higher than microwave frequencies but lower than visible light frequencies. The only variation between visible light and infrared radiation is their wavelengths. The Webb telescope would be able to see much more back in time than earlier telescopes due to its use of infrared light, helping astronomers to identify stars developing within dust. Paul Geithner discusses why the Webb telescope is mostly interested in infrared wavelengths. Because infrared waves have longer wavelengths than visible light, they can permeate through dense gases and dust areas in the galaxy with far less absorption and dispersion. As a result, infrared radiation can reveal objects in space that optical telescopes cannot see in visible light. By studying the universe at infrared wavelengths, Webb will unveil features that no other telescope has seen before. Only at infrared wavelengths can we detect the first galaxies and stars that formed after the Big Bang. The near-infrared spectrum has the advantage of being transparent to dust. This is why an optical telescope cannot see a star shrouded by dust, yet a near-infrared telescope can detect its radiation.