Related Experiment Video
Updated: May 27, 2026

Experimental Investigation of Secondary Flow Structures Downstream of a Model Type IV Stent Failure in a 180° Curved Artery Test Section
Published on: July 19, 2016
Misaligned spin and orbital axes cause the anomalous precession of DI Herculis
Simon Albrecht1, Sabine Reffert, Ignas A G Snellen
1Leiden Observatory, Leiden University, Postbus 9513, 2300 RA Leiden, The Netherlands. albrecht@space.mit.edu
Abstract:
The orbits of binary stars precess as a result of general relativistic effects, forces arising from the asphericity of the stars, and forces from any additional stars or planets in the system. For most binaries, the theoretical and observed precession rates are in agreement. One system, however-DI Herculis-has resisted explanation for 30 years. The observed precession rate is a factor of four slower than the theoretical rate, a disagreement that once was interpreted as evidence for a failure of general relativity. Among the contemporary explanations are the existence of a circumbinary planet and a large tilt of the stellar spin axes with respect to the orbit. Here we report that both stars of DI Herculis rotate with their spin axes nearly perpendicular to the orbital axis (contrary to the usual assumption for close binary stars). The rotationally induced stellar oblateness causes precession in the direction opposite to that of relativistic precession, thereby reconciling the theoretical and observed rates.
Related Concept Videos
Non-uniform Circular Motion
For example, such accelerations...
Gyroscope: Precession
Kepler's First Law of Planetary Motion
Polish astronomer Nikolaus Copernicus put forth a theory that stated a heliocentric model for the solar system. According to this heliocentric theory, all the planets, including Earth, orbit the Sun in circular orbits.
On the other hand,...
Kepler's Third Law of Planetary Motion
Rotational Motion about a Fixed Axis
Eccentricity of an Ellipse

