In the period May–July (summer in the Northern Hemisphere, winter in the Southern Hemisphere), Orion is in the daytime sky and thus invisible at most latitudes. In the tropics (less than about 8° from the equator), the constellation transits at the zenith. Orion is most visible in the evening sky from January to April, winter in the Northern Hemisphere, and summer in the Southern Hemisphere. The constellation's three-letter abbreviation, as adopted by the International Astronomical Union in 1922, is "Ori". In the equatorial coordinate system, the right ascension coordinates of these borders lie between 04 h 43.3 m and 06 h 25.5 m, while the declination coordinates are between 22.87° and −10.97°. The constellation boundaries, as set by Belgian astronomer Eugène Delporte in 1930, are defined by a polygon of 26 sides. Covering 594 square degrees, Orion ranks twenty-sixth of the 88 constellations in size. Orion is bordered by Taurus to the northwest, Eridanus to the southwest, Lepus to the south, Monoceros to the east, and Gemini to the northeast. Orion also hosts the Orionids, the strongest meteor shower associated with Halley's Comet, and the Orion Nebula, one of the brightest nebulae in the sky.Ĭharacteristics The constellation of Orion, as it can be seen by the naked eye. There are a further six stars brighter than magnitude 3.0, including three making the short straight line of the Orion's Belt asterism. Orion's two brightest stars, Rigel (β) and Betelgeuse (α), are both among the brightest stars in the night sky both are supergiants and slightly variable. Orion is most prominent during winter evenings in the Northern Hemisphere, as are five other constellations that have stars in the Winter Hexagon asterism. It is named for a hunter in Greek mythology. It is one of the 88 modern constellations it was among the 48 constellations listed by the 2nd-century astronomer Ptolemy. Orion is a prominent set of stars visible during winter in the northern celestial hemisphere. Visible at latitudes between + 85° and − 75°.īest visible at 21:00 (9 p.m.) during the month of January.
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