PlanetStar Wiki

Caelregio ['sel•rē•jē•yō] is the group of constellations within a particular region of the sky. There are 11 caelregios along with 88 constellations on the celestial sphere, that means that the average number of constellations in each caelregio is exactly eight. The caelregios are Araneus, Avis, Felis, Hippocampus, Malus, Noctua, Selachimorphus, Simianus, Solarium, Tarandus, and Testudo.


After PlanetStar learned about the Constellation Family on Wikipedia, he finds that some of that grouping is separated. He thought about the alternative way to group those constellations altogether. In February 2008, he grouped those constellations into what was called lactoph until January 1, 2011 when he renamed it to caelregio.


Like Constellation Families, caelregios was named after their most important constellation, mythological and astrological associations, and scientist who invented the constellations. However in January 2010, he renamed it all. Like constellations, caelregios are now named after the animals, instruments, or structure in Latin or Greek. In December 2010, he renamed two caelregios: Aqua the water to Chtapodi the octopus, and Vexilius the flag to Simianus the monkey. In July 2012, he renamed Chtapodi to Hippocampus the seahorse.

Seven caelregios are named after the former constellationFelis the cat, Hippocampus the seahorse, Malus the mast, Noctua the owl, Solarium the sundial, Tarandus the reindeer, and Testudo the turtle.

Constellation transfers[]

In December 2010, he transferred 15 constellations into a different caelregio, including one separate part of Serpens constellation—Serpens Cauda. He transferred some constellations to have greater symbolic relationship with other constellations in same caelregios. For example, Leo Minor and Lynx were transferred from Avis the bird to Felis the cat since these two constellations have symbolisms related to cats, thus for Leo Minor to pair up with Leo Major. Cygnus and Lyra were transferred from Tarandus the reindeer to Avis the bird since these two have symbolisms related to birds. Delphinus transferred from Tarandus to Hippocampus the seahorse and vice versa for Capricornus since Delphinus has symbolism related to a marine creature while Capricornus does not. (However Capricornus was transferred back in July 2012 since it symbolizes sea goat, not just goat.) Lastly, following the other-way around transfer in March of that year, Serpens Cauda was transferred from Tarandus back to Noctua despite it is in the sea of Tarandus to pair up with Serpens Caput which is already in Noctua and to make it easier in celestial cartography. It doesn't make sense to have one constellation located in two caelregios.

Here's the list of constellation trades from former caelregio to current caelregio.

Constellation Former caelregio Current caelregio
Aries Hippocampus Araneus
Auriga Testudo Araneus
Columba Malus Selachimorphus
Corvus Felis Noctua
Cygnus Tarandus Avis
Delphinus Tarandus Hippocampus
Leo Minor Avis Felis
Lynx Avis Felis
Lyra Tarandus Avis
Mensa Selachimorphus Solarium
Pictor Malus Selachimorphus
Serpens Cauda Tarandus Noctua
Taurus Hippocampus Araneus
Vulpecula Tarandus Testudo


Caelregio is named after the Latin words caeli meaning "sky" and regio meaning "region." It would directly combine to form caeliregio but I don't want the i betweel l and r so it sounds better without that i. Caelregio literally means "sky region" in Latin while constellation literally means "group of stars" in Latin.


Like constellations, Bayer and Flamsteed designations can also be incorporated into caelregios. For example, the star Betelgeuse in addition to being designated α Orionis or 58 Orionis, it can also be designated ε Arani or 308 Arani, since the constellation Orion is located in the caelregio Araneus.

In each caelregio, Bayer letters are sorted alphabetically in order of decreasing brightness or increasing magnitude, sorting through Greek letters then Latin letters. Since there are 50 letters between Greek and Latin, only the 50 brightest stars in each caelregio receive Bayer designation. However, same letters can be used more than once but with number superscript if the stars appear very close to each other such as in binaries or multiples, so more than 50 stars in each caelregio can receive Bayer. The Flamsteed numbers increase in order of increasing right ascension or further eastwards. However like Bayer letters, Flamsteed numbers can be used more than once but with capital Latin letter after the genitive or the decimal number if the stars are members of binaries, multiples, or doubles.

The maximum caelregio Flamsteed numbers are much higher than the maximum constellation Flamsteed numbers. The highest maximum caelregio Flamsteed number belongs to 555 Simiani, which is the star β Coronae Australis or 29 Coronae Australis. The highest Flamsteed number in a constellation belongs to 186 Centauri or 305 Simiani. However, Selachimorphus is the only caelregio with a lower maximum Flamsteed number than the only constellation Centaurus. Its maximum number is 174 Selachimorphi or υ Selachimorphi which belongs to α Volantis or 19 Volantis.


Caelregios are the group of constellations like continents are the group of countries. The largest caelregio in area is Hippocampus while the smallest caelregio is Selachimorphus, which is still larger than the largest constellation Hydra. Like constellations, caelregios are outlined with vertical and horizonal lines but not diagonal lines nor arcs. But because the constellation boundaries were drawn up in 1930 by Eugène Delporte based from the 1875 epoch, almost 8 decades before I drew caelregio boundaries, the boundaries had since been drifted way from being perfectly horizontal and vertical. Caused by the precession of the equinoxes, the caelregio and constellation boundaries will get more diagonal over time.

There are six northern caelregios and five southern caelregios along with 36 northern constellations and 52 southern constellations, that means that southern caelregios tend to contain more constellations than in the northern. There are six western caelregios and five eastern caelregios along with 44 western constellations and 44 eastern constellations, that means that eastern caelregios tend to contain more constellations than in the western. The average number of constellations in northern caelregios is six, the southern average is about 10, the western is about 7, and the eastern is about 9. There are two caelregios that are located entirely in the northern hemisphere, four entirely in the southern hemisphere, one in the western, and three in the east. The north celestial pole points to Avis while the south celestial pole points to Solarium.

Noctua is the only caelregio that is not altogether since it contains the only separated constellation Serpens. Ophiuchus, that borders two parts of Serpens, is located in Tarandus. The tiny region of Noctua in the sea of Tarandus can be pictured as an owl's feather on a reindeer.

List of caelregios[]

Caelregio Abbrev. Genitive Symbolism Constellations
Araneus Arn Arani Spider Aries, Auriga, Canis Major, Canis Minor, Gemini, Lepus, Monoceros, Orion, Taurus
Avis Avi Avis Bird Camelopardalis, Cygnus, Draco, Lyra, Ursa Major, Ursa Minor
Felis Fel Felis Cat Cancer, Crater, Hydra, Leo Major, Leo Minor, Lynx, Sextans
Hippocampus Hip Hippocampi Seahorse Aquarius, Capricornus, Cetus, Delphinus, Eridanus, Phoca, Pisces
Malus Mal Mali Mast Antlia, Carina, Puppis, Pyxis, Vela
Noctua Noc Noctae Owl Boötes, Canes Venatici, Coma Berenices, Corona Borealis, Corvus, Libra, Serpens, Virgo(note: part of Serpens is separated from the rest of Noctua by Tarandus)
Selachimorphus Sel Selachimorphi Shark Caelum, Columba, Dorado, Horologium, Hydrus, Pictor, Reticulum, Volans
Simianus Sim Simiani Monkey Ara, Centaurus, Chamaeleon, Circinus, Corona Australis, Crux, Lupus, Musca, Norma, Scorpius, Triangulum Australe
Solarium Sol Solaris Sundial Apus, Fornax, Grus, Indus, Mensa, Microscopium, Octans, Pavo, Phoenix, Sculptor, Telescopium, Tucana
Tarandus Tar Tarandi Reindeer Aquila, Hercules, Ophiuchus, Sagitta, Sagittarius, Scutum(note: Tarandus encloses part of Serpens, which is part of Noctua)
Testudo Tes Testudi Turtle Andromeda, Cassiopeia, Cepheus, Equuleus, Lacerta, Pegasus, Perseus, Triangulum Boreale, Vulpecula