The apparent shift in position of stars due to Earth's orbital motion around the Sun, similar to how raindrops appear to slant when you're moving in a car. This phenomenon causes stars to trace small elliptical paths in the sky over the course of a year.
From Latin 'stellaris' (of the stars) and 'aberratio' (a wandering away). First discovered by astronomer James Bradley in 1728 while attempting to measure stellar parallax, it became the first direct proof of Earth's orbital motion around the Sun.
Stellar aberration was astronomy's first smoking gun for Earth's motion! Bradley discovered it accidentally while trying to prove something else entirely - a perfect example of how the universe reveals its secrets when we least expect it. The effect is tiny (about 20 arcseconds maximum), but it provided undeniable evidence that Earth really does orbit the Sun, not the other way around.
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