Teach Astronomy – Resolving the Nebula

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The first step in understanding the nature of the nebulae involve resolving the nebulae. As newer, larger telescopes were built near the beginning of the twentieth century astronomers gained powerful tools to break up the diffuse light of the nebulae into the pinpoint light of many stars. Remember that the resolution of a telescope increases with its size, subject to the limitation of the Earth’s atmosphere. In the early twentieth century Edward Fath and other astronomers had noted the pinpoint light that composed the nebulae and, using a similar logic to the idea that the stars are much more distant than the Sun as given by their relative brightnesses and the inverse square law, deduced that if the pinpoint light in the nebulae were related to the starlight of the Milky Way, those stars must be extremely distant, far more than the distance to the edge of the Milky Way galaxy. This evidence, however impressive, is still indirect, and it took Edwin Hubble and his use of Cepheid variables to clench the fact that at least one of the nebulae, the Andromeda nebula, was remote from the Milky Way itself.

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