Webb's Science Tools
Webb's four scientific instruments will examine the universe across a range of near- and mid-infrared wavelengths (and even some of the red band of visible light). Each instrument has unique features that will allow astronomers to study a variety of astronomical objects in different ways.
Near Infrared Camera (NIRCam)
NIRCam will look at near-infrared wavelengths (called "near-infrared" because these wavelengths are near the red end of the visible spectrum). It will detect light from the earliest stars and galaxies in the process of formation, stars in nearby galaxies, as well as young stars in the Milky Way, and objects from a distant region of our solar system called the Kuiper Belt.
Near Infrared Spectrograph (NIRSpec)
NIRSpec is a "multi-object near-infrared spectrograph." A spectrograph is a device that breaks light up into its component colors. NIRSpec will see near-infrared wavelengths and will be able to observe more than 100 objects simultaneously thanks to its innovative microshutter assembly. It is designed to study, among other things, star formation and the chemical composition of young, distant galaxies.
Mid-Infrared Instrument (MIRI)
MIRI will have a sensitive camera and a spectrograph that will study mid-infrared wavelengths, examining distant stellar populations, the physics of newly forming stars, and the sizes of faintly visible comets and Kuiper Belt objects. MIRI is also equipped with a coronagraph, which blocks the glare of bright objects to allow clear observations of faint objects close to it.
Fine Guidance Sensors/Near-Infrared Image and Slitless Spectrograph (FGS/NIRISS
FGS is Webb's guide camera, which helps point the telescope. NIRISS will gather spectra (like NIRSpec), and photograph the universe at near-infrared wavelengths (like NIRCam), observing both extremely bright objects as well as faint objects near bright stars, such as planets. FGS and NIRISS have different purposes but are packaged together into one unit.