WHY INFRARED?

We normally think of astronomy in terms of visible light, because that’s what our eyes and traditional telescopes see. But astronomical objects produce emissions across the whole of the electromagnetic spectrum, from long-wavelength radio waves to short-wavelength X-rays and gamma rays. Our eyes evolved to see the wavelengths they do because that’s where the Sun emits most of its energy, but cooler objects – such as planets and newly formed stars – tend to radiate at longer wavelengths than this. This is one reason why infrared telescopes such as Webb – and its predecessor, NASA’S Spitzer Space Telescope, which operated between 2003 and 2020 – are so important. A second reason is that while the dust in galaxies absorbs visible light, it’s virtually transparent to infrared waves. This means even Sun-like stars can be easier to see in the infrared if there’s a lot of intervening dust.