Definitions

from The American Heritage® Dictionary of the English Language, 5th Edition.

  • noun The point at which an object is farthest away from the center of mass of the star it is orbiting.

from The Century Dictionary.

  • noun In astronomy, that part in the orbit of a double star where it is furthest from its primary.

from the GNU version of the Collaborative International Dictionary of English.

  • noun (Astron.) That point in the orbit of a double star where the smaller star is farthest from its primary.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

  • noun astronomy The point of greatest separation between two stars, especially in a binary star situation.

Etymologies

from The American Heritage® Dictionary of the English Language, 4th Edition

[ap(o)– + Greek astron, star (probably on the model of aphelion); see ster- in Indo-European roots.]

from Wiktionary, Creative Commons Attribution/Share-Alike License

apo- +‎ astron

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Examples

  • The station was outward bound for the apastron of its shortened and cometary path.

    Starfarers Anderson, Poul, 1926- 1998

  • They had already passed apastron and were downward bound.

    Starfarers Anderson, Poul, 1926- 1998

  • In this region, nearing apastron, no unusual velocity change was needed to alter orbit radically.

    Starfarers Anderson, Poul, 1926- 1998

  • Nevertheless the ship took days, terrible days to reach apastron.

    Explorations ANDERSON, Poul 1981

  • Now, at apastron, with Vixen's atmosphere to filter its radiation, the sun might almost have been Sol: smaller, brighter, but gentle in a blue sky where tall white clouds walked.

    Agent Of The Terran Empire Anderson, Poul, 1926- 1965

  • These orbs complete a revolution in 180 years, and when in apastron are seventeen times more remote from each other than when at periastron.

    The Astronomy of Milton's 'Paradise Lost' Thomas Nathaniel Orchard

  • Any approach to, or recession from this point, must occur simultaneously with each; they must always occupy corresponding parts of their orbits, and be in apastron and at periastron in the same period of time.

    The Astronomy of Milton's 'Paradise Lost' Thomas Nathaniel Orchard

  • Consequently, neither star can approach or recede from this point without the other affecting a similar motion, they must be at periastron and apastron together, and any acceleration or retardation of speed must occur simultaneously with each.

    The Astronomy of Milton's 'Paradise Lost' Thomas Nathaniel Orchard

  • The eccentricity of their orbit approaches in form that of Faye's comet, which travels round the Sun; consequently the stars, when at apastron, are twice their periastron distance.

    The Astronomy of Milton's 'Paradise Lost' Thomas Nathaniel Orchard

  • The pair travel in an orbit from fourteen to forty-two times the radius of the Earth's orbit; so that when at apastron they are three times as distant from each other as when at periastron.

    The Astronomy of Milton's 'Paradise Lost' Thomas Nathaniel Orchard

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