Oddball Stars Explained: New Observations Solve Longstanding Mystery Of Tipped Stars

This artist's conception of the double-star system DI Herculis illustrates the key findings from the new research. Spectroscopic observations showed that the two stars are both tipped over almost horizontally, relative to the plane of their orbits around each other. Because they are rotating rapidly which creates equatorial bulges, the tidal interactions between the two slows down a regular variation in the plane of the orbits, called precession -- a slowing that had been a mystery for three decades. (Credit: Courtesy of Simon Albrecht)

From Science Daily:

ScienceDaily (Sep. 18, 2009) — A pair of unusual stars known as DI Herculis has confounded astronomers for three decades, but new observations by MIT researchers and their colleagues have provided data that they say solve the mystery once and for all.

It has long been clear that there was something odd going on in this double-star system, but it wasn't clear just what that was. The precession of the orbits of the two stars around each other — that is, the way the plane of those orbits change their tilt over time, like the wobbling of a top as it winds down — seems to take place four times more slowly than established theory says it should. The anomaly is so unexpected that at one point it was seen as possible evidence against Einstein's long-accepted theory of relativity.

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