- Question 2:
- Why are infrared telescopes placed in space?
Student answers should include the following ideas:
Although there are many infrared telescopes on Earth, the best place to do infrared astronomy is in space. Earth's atmosphere glows brightly in infrared light, making it difficult to accurately measure light from faint celestial infrared objects. So an infrared telescope needs to be as far away from Earth as possible and shielded from Earth's glow. The James Webb Space Telescope will be placed at the L2 point and will have a tennis court-sized sunshield to protect it from the infrared glow of the Sun and Earth.
Also, in contrast to visible light, which is blurred by Earth's atmosphere, infrared light is absorbed by many of the components of Earth's atmosphere, so it never reaches the ground. Water vapor, in particular, absorbs many wavelengths of infrared light. An astronomer, for example, would have a hard time using a ground-based infrared telescope to search for water vapor (an indication of habitability) in the atmosphere of an extrasolar planet. Most of the infrared light from that planet would not reach the telescope because the water vapor in Earth's atmosphere would absorb it.
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