How Telescopes Work
Know that telescopes are instruments that help us see distant objects in space, and that space telescopes like Hubble and James Webb orbit above Earth's atmosphere to get clearer views of the universe
What a learner can do afterwards
- Explain that a telescope magnifies distant objects so we can see them in more detail
- State that Earth's atmosphere blurs the view, so space telescopes get clearer pictures
- Name at least one space telescope (Hubble or James Webb) and describe what it does
1 · Read
Stars, planets, and galaxies are so far away that they look like tiny dots, even on a clear night. A telescope is a tool that gathers light and makes faraway things look much bigger and closer, so we can see details our eyes alone would miss.
Here on Earth, we look up through a thick layer of moving air called the atmosphere. That air bends and shifts the light coming from space, so even a good telescope on the ground gets a slightly blurry view, like looking through rippling water.
To get a clearer view, scientists built the Hubble Space Telescope and sent it into orbit far above the atmosphere. From up there, Hubble takes sharp, clear pictures of distant galaxies that telescopes on the ground could never capture.
The James Webb Space Telescope also orbits above the atmosphere. It uses special heat-sensing cameras to spot things too dim and too far away for our eyes, or even Hubble, to see.
Telescopes magnify faraway things, and space telescopes like Hubble and James Webb see the clearest because they orbit above Earth's blurry atmosphere.
More to read
6.5 Observations outside Earth's Atmosphere
Telescopes gather light from distant objects so we can see them in detail. Earth's atmosphere blurs the view, like looking through rippling water. It also blocks most light that is not visible, such as ultraviolet, X-rays, and gamma rays. Space telescopes orbit above the atmosphere. Hubble has given us sharp visible and ultraviolet images for over 30 years. The James Webb Space Telescope sees in infrared, letting it peer through dust clouds to watch stars and galaxies being born. Both telescopes have changed our understanding of the universe.
Thinking Ahead
Before Hubble, all telescopes were on the ground. Astronomers dreamed of putting them in space to escape the blurring atmosphere. Hubble launched in 1990 with a flawed mirror. A repair mission in 1993 fixed it. Since then, Hubble has measured the expansion rate of the universe, watched planets form around other stars, and taken the deepest images of distant galaxies. The James Webb Space Telescope launched in 2021. Its 6.5-metre mirror folds up for launch and unfolds in space. It operates at very cold temperatures to detect faint infrared light.
Thinking Ahead
Future space telescopes will be even more powerful. Concepts include a starshade that flies thousands of kilometres in front of a telescope to block a star's glare so we can see its planets directly. Another idea is an interferometer that combines light from multiple telescopes flying in formation to achieve the resolution of a single giant mirror. These missions could one day take pictures of Earth-like planets around other stars and search their atmospheres for signs of life.
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8 questions wait behind this lesson, each with its answer explained. Every answer feeds the sky: stars light as they are learned, and dim when it is time to come back.