Definition of "periastron" [per•i•as•tron]

• That point of the orbit of a celestial body which is closest to the star around which the body is orbiting. (noun)

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• "In this scenario, as a smaller companion in the system came on its closest approach periastron the outer layers of the LBV, which are already unstable and loosely bound due to the size of the star, are pulled off due to tidal forces."
• "With these simple starting parameters, Kashi showed that it was possible to produce a situation in which the onset of eruptions was similar to the periastron approach."
• "I therefore predict that a continuous 7 year long observation of pronounced lines may reveal a small doppler shift variation, close to the periastron passage."