Telescopes for every kind of light

0:00Do telescopes only collect visible light, the light our eyes can see?

0:05Here is a spiral galaxy in visible light: its stars, and dark lanes of dust that block light.

0:13But visible light is one part of the electromagnetic spectrum, the whole range of light.

0:19The kinds of light differ in wavelength, the distance from one wave crest to the next.

0:25Four of them, from longer waves to shorter, are radio, infrared, visible light and X-rays.

0:33Radio waves show the galaxy's cold gas, which often spreads wider than its stars.

0:39Radio telescopes are big dishes, often linked in an array that works as one giant telescope.

0:47Radio waves pass through the atmosphere and clouds, so the dishes work in daylight and cloudy weather.

0:54Infrared light passes through dust, so it shows stars that the dust hides in visible light.

1:00The James Webb Space Telescope, launched in 2021, sees infrared and finds very distant galaxies.

1:09As the universe expands, their light is stretched to longer, infrared waves. This is called redshift.

1:17X-rays show very hot gas, at millions of degrees, such as gas swirling near black holes.

1:24Our atmosphere blocks X-rays, so X-ray telescopes are placed in space, above it.

1:30Moving air blurs starlight, so space telescopes such as Hubble, launched in 1990, avoid that blur.

1:39So telescopes collect many kinds of light, not just visible, and each shows something new.