What is Cosmological Redshift?
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NASA/ESA/CSA/STScI
The universe is expanding, and that expansion stretches light traveling through space in a phenomenon known as cosmological redshift. The greater the redshift, the greater the distance the light has traveled. As a result, telescopes with infrared detectors are needed to see light from the first, most distant galaxies.
Credits
Illustration
NASA, ESA, Leah Hustak (STScI)