[Home]Astronomical aberration

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Astronomical Aberration is a well known physical phenomenon dealing with light and the position of objects.

When observed from the Earth, light from the Sun or any other astronomical object shows astronomical aberration. The phenomenon is also known to work for non-astronomical objects, but they usually are so close there is no way to measure it, since the speed of light is so fast. For the Sun, it is known that light takes about 8.3 minutes to come to the Earth. While the light is traveling, the Sun appears to move through an angle of about 20 arc seconds. Therefore the light is actually showing where the Sun was 8.3 minutes ago. The actual instantaneous position of the Sun differs from its apparent position by about 20 arcs seconds east. We will see the Sun in its true present position about 8.3 minutes into the future (which is how long it takes for the light to reach our eyes). This phenomenon is also true for stars. Their positions are displaced from their average position by up to 20 arcs seconds, the variation is actually dependent upon the Earth's motion around the Sun, and its relative direction from the particular star.

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Last edited September 14, 2001 11:30 pm by BenBaker (diff)