Sunday, 17 March 2013

universe - Why when we look through a telescope in space, do the billions of stars not block our view from seeing further?

Yes they do, or rather not the stars but the dust and gas nebulae that are between them. However this is only a serious problem when we are looking through our own galaxy towards more distant objects.



Look at this apod from Jan 16 2016: It shows a relativly nearby galaxy, and one that would be a fairly easy object for amateur telescopes, if it were not aligned to the edge of the milky way in Cameleopardis. It can be seen, but only through a mess of nearby stars and gas. Galaxies that are behind the galactic centre in Sagittarius would be essentially invisible.



However, if we are not looking through our galaxy, but out of it, the nearby stars don't block our view this is because stars are so small compared to interstellar distances: If the sun were the size of a football, then Alpha Centuari would be on the other side of the world.

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