The Collaborative International Dictionary
Periastron \Per`i*as"tron\, n. [NL., fr. Gr. ? about + ? a star.] (Astron.) That point, in the real or apparent orbit of one star revolving around another, at which the former is nearest to the latter.
Wiktionary
n. (context astronomy English) That point of the orbit of a celestial body which is closest to the star around which the body is orbiting.
Usage examples of "periastron".
The planet and its sister planets were approaching periastron, the nearest point in the orbit to the brilliant star known as Freyr.
Its pull on the ocean mass was now, only 118 Earth years from periastron, considerable.
Avernus were recording details of increasing volcanic activity on the world approaching periastron below.
After capture, the atmospheric carbon dioxide was much reduced, combining at periastron with water to form carbonate rocks.
It slid back now, with its planets and its wide-spun halo, toward one more periastron passage.
It was still half a day till periastron, and they would remain there until then.
It seems that the government here knew all about the weather conditions they could expect at periastron, and had made plans for them.
Secour-B was home to a small industrial presence, but Secour-C never approached to within less than thirty-six light-hours of Secour-A even at periastron, and there was nothing of sufficient value to bring anyone here.
Freyr receded day by day and decade by decade from Helliconia and its sister planets- as the 236 astronomical units of periastron between Batalix and Freyr lengthened to the formidable 710 of apastron-the young on the Ob servation Station rose up in despair and overthrew their masters.
The red-dwarf stellar companion, nearing periastron but still over nine hundred light-minutes away, was visible only as a dim, ruddy star.
Even at periastron, it barely swung within three light-hours of Component A.