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Ask an Astrophysicist

The Question

(Submitted January 17, 1999)

I'm in 12th grade and plan to major in astrophysics in college. But I was wondering, what are problems with ground-based telescopes? Why is the HST more effective than telescopes on the ground?

The Answer

The short answer is that ground-based telescopes have to look through the Earth's atmosphere. The stars appear to twinkle when we look up at the night sky because their light has to pass through air which is moving and is at different temperatures, and thus has different refractive indices. To get a clearer view, the Hubble Space Telescope was placed in orbit, above the Earth's atmosphere.

You can find out more about the Hubble Space Telescope at:

Damian Audley and Sean Scully
for Ask an Astrophysicist.

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