apsis

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Related to Periastron: periapsis, Pericenter
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Synonyms for apsis

a domed or vaulted recess or projection on a building especially the east end of a church

References in periodicals archive ?
During the past 11 years, spanning three periastron passages, the Goddard group has developed a model based on routine observations of the stars using ground-based telescopes and multiple NASA satellites.
This effect is even more sensitive to the orbital parameters than the periastron precession is.
Their orbit is highly elliptical; at the far end of the ellipse the two stars are 30 astronomical units apart, but around periastron they rapidly dip to within about 2 a.
This prediction comes from "definitive" new orbital elements for the binary published in 2007, based partly on speckle-interferometry measurements made during the critical time around the 2005 periastron and closest separation (0.
To compute a really accurate orbit, you need to observe the stars near periastron, when they're closest, and most strongly affected by each other's gravity.
In 2035 the stars will be at periastron, closest together in space.
At the time of periastron (closest orbital approach) in May 2005 they were just 0.
Its periastron (when the two stars of a binary are closest together in space) probably came in April 2005 with the stars just 0.
88[degrees]-per-year advance--the largest ever observed--is 140,000 times greater than the relativistic precession of Mercury's perihelion and four times larger than the periastron advance of the Taylor-Hulse binary pulsar.
6-inch Dorpat refractor in Russia (see page 70 of the May/June 2005 Night Sky), managed to measure the pair near the time of periastron.