What did early spectroscopic measurements show about spiral nebulae?

Question

Quizplus · Accepted Answer

Early spectroscopic measurements showed that most spiral nebulae had redshifted spectra, indicating that they were moving away from us and therefore were not part of our own galaxy. This was a key piece of evidence in the development of the idea that the universe is expanding. The other choices are incorrect as spiral nebulae were found to be rotating, and some are still thought to be gas clouds rather than individual stars. Additionally, many spiral nebulae are located outside of our own galaxy.

What Did Early Spectroscopic Measurements Show About Spiral Nebulae