History of the Universe eBook. 398 pages, 300 illustrations only £5.99
To early astronomers with low resolution telescopes, these clouds looked like distant planets.
Cats Eye Nebula image courtesy of: X-ray: NASA/CXC/SAO; Optical: NASA/STScI
In fact they are clouds of gas blown away by the death of small to medium red giant stars, such as the Sun will eventually become. The nucleus of the star remains as a white dwarf star.
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