Constellation Triangulum (Triangle)

Triangulum: IAU Constellation Map [150]


Triangulum with an area of 132 square degrees is a small, not particularly bright but distinctive constellation with the shape of a long, right-angled triangle. It lies between Andromeda, Perseus, Aries and Pisces. The center culminates around midnight on October 23rd. [9, 15]

Stars with Proper Names [154]
α Tri Metallah, Mothallah, Atria, Caput Trianguli, Ras Al Muthallah, Elmuthalleth
Data for constellation Triangulum [150]
IAU NameTriangulum
IAU GenitiveTrianguli
IAU Abbr.Tri
English NameTriangle
Opposition26 October
Season (47° N)June … March
Right Ascension01h 31m 28s … 02h 50m 40s
Declination+25° 36' 18" … +37° 20' 50"
Area132 deg2
Neighbours (N↻)And, Psc, Ari, Per

Deep-Sky Object Descriptions


Constellation Triangulum
Constellation Triangulum: Illustration from «Uranometria» by Johann Bayer, copper engraving by Alexander Mair, 1603 [28]

Mythology and History

There are some interpretations for this constellation. The Greeks called it Deltoton, the Romans Triangulum and the Arabs El Muthalleth, which also means triangle. Some say that Triangulum also represents the island of Sicily, which was honored by Zeus by the fact that its image can be seen under the stars. One of the earlier names of Triangulum was Sicilia. Aratos von Soli describes this place as follows: «Near Andromeda is the island of Sicily, which resembles a triangle, the shorter part of which is adorned with closely spaced asterisks.» For the Egyptians, this constellation was a symbol of the Nile Delta and an honor for the Alexandrian sciences. [7, 21]


  • [7] «Der grosse Kosmos-Himmelsführer» von Ian Ridpath und Wil Tirion; Kosmos Verlag; ISBN 3-440-05787-9
  • [9] «Drehbare Sternkarte SIRIUS» von H. Suter-Haug; Hallwag-Verlag, Bern
  • [15] «Hartung's Astronomical Objects for Southern Telescopes» by David Malin and David J. Frew; Melbourne University Press 1995; ISBN 0-522-84553-3
  • [21] «Taschenatlas der Sternbilder» von Josef Klepesta und Antonin Rükl; Verlag Werner Dausien; ISBN 3-7684-2384-0
  • [28] «Uranometria omnium asterismorum continens schemata, nova methodo delineata aereis laminis expressa» Johann Bayer, Augsburg, 1603; DOI:10.3931/e-rara-309
  • [150] IAU: The Constellations, 11. Oktober 2020;
  • [154] Yale Bright Star Catalog, 15. Oktober 2020;