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Towards the end of the 20th century, technological improvements helped to further the study of planetary nebulae.
Space telescopes allowed astronomers to study light emitted beyond the visible spectrum which is not detectable from ground-based observatories ( because only radio waves and visible light penetrate the Earth's atmosphere ).
Infrared and ultraviolet studies of planetary nebulae allowed much more accurate determinations of nebular temperatures, densities and abundances.
Charge-coupled device technology allowed much fainter spectral lines to be measured accurately than had previously been possible.
The Hubble Space Telescope also showed that while many nebulae appear to have simple and regular structures from the ground, the very high optical resolution achievable by a telescope above the Earth's atmosphere reveals extremely complex morphologies.

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