Constellations: Monoceros 'the Unicorn'
Created | Updated Nov 8, 2017
Constellations: Overview
| Andromeda
| Antlia
| Apus
| Aquarius
| Aquila
| Ara
| Aries
| Auriga
| Boötes
| CaelumCamelopardalis | Cancer | Canes Venatici | Canis Major | Canis Minor | Capricornus | Carina | Cassiopeia | Centaurus
Cepheus | Cetus | Chamæleon | Circinus | Columba | Coma Berenices | Corona Australis | Corona Borealis | Corvus
Crater | Crux | Cygnus | Delphinus | Dorado | Draco | Equuleus | Eridanus | Fornax | Gemini | Grus | Hercules | Horologium
Hydra | Hydrus | Indus | Lacerta | Leo | Leo Minor | Lepus | Libra | Lupus | Lynx | Lyra | Mensa | Microscopium | Monoceros
Musca | Norma | Octans | Ophiuchus | Orion | Pavo | Pegasus | Perseus | Phoenix | Pictor | Pisces | Piscis Austrinus
Puppis | Pyxis | Reticulum | Sagitta | Sagittarius | Scorpius | Sculptor | Scutum | Serpens | Sextans | Taurus
Telescopium | Triangulum | Triangulum Australe | Tucana | Ursa Major | Ursa Minor | Vela | Virgo | Volans | Vulpecula
The unicorn... because of its intemperance, not knowing how to control itself before the delight it feels towards maidens, forgets its ferocity and wildness, and casting aside all fear it will go up to the seated maiden and sleep in her lap, and thus the hunter takes it.
– Leonardo da Vinci
Unicorns, horses with a single horn protruding from their forehead, are legendary magical creatures whose blood can supposedly render immortality upon the drinker. However, to slay a unicorn was said to condemn one's soul to eternal damnation.
In ancient Babylon, the cradle of civilisation, people worshipped the unicorn as far back as 3500 BC. The most widely accepted reason for the unicorn's extinction was that they preferred to play in the rain rather than accept Noah's invitation to board the Ark. Consequently, none were saved to repopulate the Earth after the Great Flood. One which is still around but never seen is, of course, the invisible pink unicorn.
The Constellation Monoceros the Unicorn
| Name: | Monoceros (Greek: 'one horn') |
| Genitive: | Monocerotis |
| Short form: | Mon |
| Area: | 482 sq deg |
| Co-ordinates1: | Right Ascension 07h, Declination −05° |
| Origin: | Modern |
The constellation Monoceros, literally 'one horn', is situated between Orion and Hydra, with Orion's hunting dogs Canis Minor above and Canis Major below. Monoceros also shares its borders with Gemini, Lepus and Puppis. The unicorn straddles the brightest star in the night sky, Sirius (alpha Canis Majoris).
A unicorn2 is mentioned in the Old Testament of the Bible. Because of this, the Dutch cartographer Petrus Plancius (1552 - 1622) is credited with introducing the constellation. Johann Bayer (1572 - 1625) included Monoceros in his Uranometria, a 1603 sky atlas.
Stars
The scientific star names are simple to understand (if you know your Greek alphabet). For example: 'alpha Monocerotis' means it is the brightest star in the constellation Monoceros. The next brightest is designated 'beta', and so on. Combined with the genitive name, this is known as the 'Bayer designation'. Some stars have proper names as well, for example, alpha Monocerotis is Ctesias. Others are known by their catalogue number.
Monoceros Stars
There are no stars above fourth magnitude in the unicorn, so Monoceros is not a prominent constellation. Sometimes stars fluctuate in brightness, or small errors were made at the time of measuring, so the scientific designations are a little off. In this case the brightest star of the constellation is the beta star Cerastes - a magnificent three-star system which forms a triangle shape. Its discoverer, Sir William Herschel, described it as 'one of the most beautiful sights in the heavens'.
R Monocerotis is (probably) a rare, isolated, massive star surrounded by NGC 2261, known as Hubble's Variable Nebula. Some astronomers dismiss the existence of R Monocerotis, as it does not display a normal stellar spectrum. It was not even listed in the official 2000 sky atlas. Other prominent astronomers insist it is an irregular variable star, may be a protoplanetary system, and is the fuelling source of Hubble's Variable Nebula.
We know the nebula exists so, to try to solve the puzzle, the area has been studied extensively by powerful telescopes at the Mauna Kea Observatories in Hawaii. Other data was collated by the Hubble Space Telescope. The conclusion is that R Monocerotis is probably an RW Aurigae-type variable with a T Tauri-type dwarf star companion. So we're going to have to live with the mystery a while longer.
S Monocerotis is not that unusual a star, except when hosted by the Astronomy Picture of the Day website: you not only see the bright star with its companions but also the fabulous red gas and blue reflection of two nebulae and two star clusters. Where the two colours mix is a lovely shade of pink. What a diva! S Monocerotis is visible to the naked eye. But you need a powerful optical lens to view the surrounding nebulosity of NGC 2264.
Plaskett's Star is the most massive binary system found at the time of writing. Consisting of two blue giant stars, the system was discovered in 1922 and studied extensively by Canadian astronomer John Stanley Plaskett, who had helped to persuade his government to build the Dominion Astrophysical Observatory near Victoria, British Columbia. It housed a 72-inch (183cm) reflecting telescope, the biggest in the world in the early 20th Century.
The 2002 nova V838 Monocerotis can be seen rapidly expanding in the NASA HubbleSite images. The star is a supergiant, 20,000 light years3 away, at the outer edge of our Milky Way galaxy. In 2004 a new Hubble image of the expanding halo surrounding the star was likened to Starry Night, a painting by Vincent van Gogh.
Star Table
| Star | Designation | Name or
catalogue number | Brightness (m) | Distance
(light years) | Spectral classification and/or comments |
| β Mon | beta Mon | Cerastes | +3.7 | 690 | Triple star system |
| α Mon | alpha Mon | Ctesias | +3.9 | 144 | Yellow giant |
| γ Mon | gamma Mon | Tempestris | +3.9 | 645 | Orange giant |
| δ Mon | delta Mon | Kartajan | +4.1 | 370 | White dwarf |
| ζ Mon | zeta Mon | 29 Mon | +4.3 | 1,800 | Yellow giant |
| ε Mon | epsilon Mon | 8 Mon | +4.4 | 130 | White subgiant |
| S Mon | HD 47839 | 15 Mon | +4.6 var | 1,000 | Blue giant |
| HR 2422 Mon | GC 8631 | Plaskett's Star | +6.05 | 6,600 | Massive binary star system |
| V838 Mon | GSC 04822-00039 | Nova Monocerotis 2002 | Var | 20,000 | Major outburst 2002 |
Red Rectangle Nebula
The webbed, X-shaped protoplanetary Red Rectangle Nebula creates an intriguing mystery: why is it such a strange shape? It has been speculated that the central binary star system creates a pair of jets that spin. More than 2,300 light years away, we see the 'drag' of the fast spinning, suspended like the still of a film stuck on freeze-frame; hence the webbed effect between the jets.
New General Catalogue (NGC)
The NGC was compiled by John Louis Emil Dreyer (director of the Armagh Observatory from 1882 - 1916).
NGC in Monoceros
NGC 2261 aka Hubble's Variable Nebula is illuminated by the star R Monocerotis, which has ten times the mass of our own Sun. It is thought the nebula changes shape every month because the dust and gas pass so close to R Monocerotis that they are affected by its solar wind. The gasses excite and flare up, and the movement creates shadows on the rest of the nebula. Edwin Hubble took great fancy to this unusual nebula and, in his honour, it was subsequently named after him.
NGC 2264 is the designation for four objects: the Christmas Tree Cluster, the Snowflake Cluster, the Cone Nebula and the Fox Fur Nebula.
NGC 2237 aka the Rosette Nebula has several super-hot blue giant stars which emit radiation and intense solar winds, making the surrounding area particularly volatile. If there are any cooler stars in the way of these dangers, their planet-forming dust is likely to be blown away. The safe zone is reckoned to be 1.6 light years (ten trillion miles).
There is one Messier object in Monoceros - an open star cluster which was discovered by the Italian astronomer Giovanni Domenico Cassini (1625 - 1712) prior to Messier's cataloguing of it as M50 in 1772. Its NGC designation is NGC 2323.
NGC Table
| Catalogue | Name | Type | Brightness (m) | Distance
(light years) | Remarks |
| NGC 2237 | Rosette Nebula | Emission nebula | +9 | 5,200 | X-ray emitter |
| NGC 2244 | — | Open cluster | +4.8 | 5,200 | Within Rosette Nebula |
| NGC 2261 | Hubble's Variable Nebula | Reflection nebula | +9 | 2,500 | Fan-shaped nebula illuminated by
R Monocerotis |
| NGC 2264 | — | Four objects | +3.9 | 2,600 | Two nebulae and two clusters |
| NGC 2323 | M50 | Open cluster | +6 | 3,200 | Early Cassini discovery |
Extrasolar Planets in Monoceros
Many extrasolar planetary systems have been found in the constellation Monoceros up to 2009; the first was discovered in 2000. The figures given in the table below are the length of the planet's orbital period around its parent star, which we know of as a year. The mass of the extrasolar planet is compared with that of Jupiter, our solar system's largest planet. It is known by astronomers as the 'Jovian scale'.
The planet CoRoT-1 b in Monoceros was the first to be discovered by the French-led CoRoT satellite mission launched on 27 December, 2006. It is hoped the instrumentation onboard is sensitive enough to detect the passage of rocky planets transiting their stars.
Extrasolar Planets Table
| Star name or
catalogue number | Planet
catalogue number | Planet mass
(Jovian scale) | Orbital period
(Earth days) | Year of discovery | Comments |
| HD 52265 | HD 52265 b | 1.1 | 120 | 2000 | Eccentric orbit |
| HD 46375 | HD 46375 b | 0.2 | 100 | 2000 | Hot sub-Saturn |
| CoRoT-1 | CoRoT-1 b | 1.3 | 1.5 | 2007 | First CoRoT discovery |
| CoRoT-4 | CoRoT-4 b | 0.72 | 9.2 | 2008 | Hot gas giant |
| CoRoT-5 | CoRoT-5 b | 0.467 | 4.03 | 2008 | Hot gas giant |
| CoRoT-7 | CoRoT-7 b | 0.015 | 0.85 | 2009 | Hot super Earth |
| CoRoT-7 | CoRoT-7 c | 0.02 | 3.7 | 2009 | Hot super Earth |
| HD 45652 | HD 45652 b | 0.47 | 43 | 2008 | Hot gas giant |
| HD 66428 | HD 66428 b | 2.82 | 1,973 | 2006 | Orbits Sun-like star |
| HD 44219 | HD 44219 b | 0.58 | 472 | 2009 | Gas giant |
| CoRoT-12 | CoRoT-12 b | 0.9 | 2.83 | 2010 | Hot gas giant |
| CoRoT-13 | CoRoT-13 b | 1.3 | 4.04 | 2010 | Hot gas giant |
| CoRoT-14 | CoRoT-14 b | 7.6 | 1.5 | 2010 | Hot superjovian |
| CoRoT-15 | CoRoT-15 b | 63.3 | 3.06 | 2010 | Brown dwarf |
| CoRoT-18 | CoRoT-18 b | 3.5 | 1.9 | 2011 | Hot superjovian |
| CoRoT-19 | CoRoT-19 b | 1.1 | 3.9 | 2011 | Hot gas giant |
| CoRoT-20 | CoRoT-20 b | 4.24 | 9.24 | 2011 | Hot superjovian |
| CoRoT-21 | CoRoT-21 b | 2.26 | 2.72 | 2011 | Hot superjovian |
| CoRoT-24 | CoRoT-24 b | 0.1 | 5.1 | 2011 | Hot sub-Saturn |
| CoRoT-24 | CoRoT-24 c | 0.17 | 11.75 | 2011 | Hot sub-Saturn |
Unicorns in Modern Culture
The unicorn is a heraldic supporter that appears in many coats of arms, including the royal coat-of-arms of Great Britain, in which the unicorn stands for Scotland.
Powdered unicorn horn is prized for its aphrodisiac properties.
A group of unicorns appear in Disney's Fantasia.
The Qilin is a legendary Chinese unicorn.
Sir Thomas Browne stated in his Pseudodoxia Epidemica that unicorn horn was an antidote to poison.
The Honda Unicorn is a silver and black motorcycle.
In the 'Harry Potter' universe, the unicorn lives in the Forbidden Forest. The book Harry Potter and the Sorceror's Stone4 features a unicorn on the cover.
The Unicorn Tapestries are among the most beautiful and complex works of art to survive from the Middle Ages. They can be seen at The Cloisters, a branch of the Metropolitan Museum of Art, New York.
