Naked Science Forum
Non Life Sciences => Physics, Astronomy & Cosmology => Topic started by: thedoc on 02/08/2013 12:30:03
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Dave Thacker asked the Naked Scientists:
When viewing a galaxy through a telescope we see its light as I imagine our galaxy might appear if viewed from another galaxy.
If we see a galaxy brightly in a telescope, can it ever be dark on a planet it contains?
Are there segments of galaxies so bright that any point on one of its planets would be in perpetual light regardless of its own sun's set/rise cycle?
The bigger question, with light sources at every point 360x360, how does it ever get dark? Are there places that are never dark? ;-)
Dave
What do you think?
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A planet in the center of a globular cluster (http://en.wikipedia.org/wiki/Globular_cluster#Composition) would be surrounded by stars, on average separated by the width of our solar system.
The nearest star would still dominate the day/night distinction, but it would never really get dark at night.
However, such an environment would not be conducive to a stable orbit for a planet, or stable seasons; the planet would probably end up getting swallowed by a star.
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Technically the earth is never dark. Light from other stars and scattered moons, planets, the atmosphere etc. still make it to the surface. It is very faint compared to the light from the sun, but still not completely dark.
Other potential answers include: the sunny side of mercury, which is tidally locked to the sun, and always "dayltime"; the surface of a star would also be pretty unlike to be dark while the star is burning.