Abbreviation Mon Symbolism the Unicorn Declination −5.74 Bayer/Flamsteed designation 32 Stars with planets 16 | Genitive Monocerotis Right ascension 7.15 Main stars 4 Messier object 1 | |
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Pronunciation /məˈnɒsᵻrəs/,
genitive /ˌmɒnəsᵻˈroʊtᵻs/ Stars V838 Monocerotis, Plaskett's star, Alpha Monocerotis Bordering constellations Canis Major, Canis Minor, Gemini, Hydra, Lepus, Orion, Puppis Similar Lepus, Canis Minor, Canis Major, Orion, Puppis | ||
The constellation monoceros
Monoceros (Greek: Μονόκερως) is a faint constellation on the celestial equator. Its name is Greek for unicorn. Its definition is attributed to the 17th-century Dutch cartographer Petrus Plancius. It is bordered by Orion to the west, Gemini to the north, Canis Major to the south and Hydra to the east. Other bordering constellations include Canis Minor, Lepus and Puppis.
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V838 monocerotis v838 mon
Stars
Monoceros is not easily seen with the naked eye, containing only a few fourth magnitude stars. Alpha Monocerotis has a visual magnitude of 3.93, slightly brighter than Gamma Monocerotis at 3.98.
Beta Monocerotis is a triple star system, the three stars forming a triangle which seems to be fixed. The visual magnitudes of the stars are 4.7, 5.2 and 6.1. William Herschel discovered it in 1781 and commented that it is "one of the most beautiful sights in the heavens".
Epsilon Monocerotis is a fixed binary, with visual magnitudes of 4.5 and 6.5.
S Monocerotis, or 15 Monocerotis, is a bluish white variable star and is located at the center of NGC 2264. The variation in its magnitude is slight (4.2–4.6). It has a companion star of visual magnitude 8.
V838 Monocerotis, a variable red supergiant star, had an outburst starting on January 6, 2002; in February of that year, its brightness increased by a factor of 10,000 in one day. After the outburst was over, the Hubble Space Telescope was able to observe a light echo, which illuminated the dust surrounding the star.
Monoceros also contains Plaskett's Star, which is a massive binary system whose combined mass is estimated to be that of almost 100 Suns put together.
Planets
Monoceros contains two super-Earth exoplanets in one planetary system: COROT-7b was detected by the COROT satellite and COROT-7c was detected by HARPS from ground-based telescopes. Until the announcement of Kepler-10b in January 2011, COROT-7b was the smallest exoplanet to have its diameter measured, at 1.58 times that of the Earth (which would give it a volume 3.95 times Earth's). Both planets in this system were discovered in 2009.
Deep-sky objects
Monoceros contains many clusters and nebulae, most notable among them:
History
In Western astronomy, Monoceros is a relatively modern constellation. Its first certain appearance was on a globe created by the Dutch cartographer Petrus Plancius in 1612 or 1613 and it was later charted by German astronomer Jakob Bartsch as Unicornu on his star chart of 1624.
German astronomers Heinrich Wilhelm Olbers and Ludwig Ideler indicate (according to Richard Hinkley Allen's allegations) that the constellation may be older, quoting an astrological work from 1564 that mentioned "the second horse between the Twins and the Crab has many stars, but not very bright"; these references may ultimately be due to the 13th century Scotsman Michael Scot, but refer to a horse and not a unicorn, and its position does not quite match. Joseph Scaliger is reported to have found Monoceros on an ancient Persian sphere. French astronomer Camille Flammarion believed that a former constellation, Neper (the "Auger"), occupied the area of the sky now home to Monoceros and Microscopium, but this is disputed.
Chinese asterisms Sze Fūh, the Four Great Canals; Kwan Kew; and Wae Choo, the Outer Kitchen, all lay within the boundaries of Monoceros.