Thermal emission, dust and molecules
Relatively cool objects and dust can emit strongly in the infrared. Dust absorbs starlight and reradiates energy at longer wavelengths, recording how surrounding material processes radiation.
Molecular vibrations, rotations and their combinations produce spectral features useful for studying composition. Identification still requires spectra, models and observing conditions rather than an image’s display colour alone.
References: [1]
Obscured and redshifted objects
Selected infrared wavelengths reveal regions partly hidden by dust in visible light, including stellar nurseries. Transmission depends on wavelength and material rather than being an unlimited ability to see through matter.
Cosmic expansion can shift originally ultraviolet or visible emission into the infrared. Webb’s instruments cover approximately 0.6–28 micrometres, supporting studies from nearby planetary systems to early galaxies.
Atmospheric and instrument backgrounds
Atmospheric molecules absorb many infrared wavelengths, leaving discontinuous ground-based windows. Space instruments extend coverage, while favourable high-altitude sites improve selected terrestrial observations.
The telescope and instrument also emit infrared light that can overwhelm faint targets. Webb’s MIRI covers 5–28.3 micrometres and uses dedicated cooling to reduce that background, improving detection without making all targets the same kind of thermal source.