Pronunciation:

 (try-ANG-gu-lum)

Abbreviation:

 Tri

  Genitive:

 Trianguli 

Right Ascension:

 2 hours

  Declination:

 30 degrees

Area in Square Degrees:

 132

Crosses Meridian:

 9 PM, December 5

Visible Between Latitudes:

 90 and -50 degrees

The constellation Triangulum, the triangle, is completely visible in latitudes north of -53 degrees from March through May. It is a small constellation, occupying only 132 square degrees. This constellation ranks 78th in size among the 88 constellations in the night sky. It is bordered by Andromeda to the north and west, Pisces to the west and south, Aries to the south, and Perseus to the east.

Traingulum is one of the original 48 constellations first drawn by second century Greek astronomer Ptolemy. The name Triangulum is Latin for “triangle.” There is no mythology associated with this constellation. All of its historic names have been derived from its shape. In ancient times, its distinctive shape of three stars was called Deltoton because it resembled the Greek letter delta. To the ancient Egyptians, it represented the delta of the river Nile. The ancient Romans called it Sicilia because it reminded them of the island of Sicily.

The constellation Triangulum showing common points of interest
The constellation Triangulum showing common
points of interest. © Sea and Sky
Triangulum constellation map
Triangulum constellation map.
© Torsten Bronger CC BY-SA 3.0
Object
Designation
Name / Meaning
Object Type
V Mag
1 2 3 4 5
M33
Beta Trianguli
Mothalla
Gamma Trianguli
Delta Trianguli
Triangulum Galaxy
N/A
"Head of the Triangle"
N/A
N/A
Spiral Galaxy
Binary Star System
Binary Star System
Blue-White Subgiant Star
Binary Star System
5.72
3.00
3.42
4.01
4.87

Triangulum’s three brightest stars form the distinctive shape of an elongated triangle. Beta Trianguli is the brightest star. With a visual magnitude of 3.0, it is a binary star system located 127 light years from Earth. Mothalla is the second brightest star with a magnitude of 3.42. It is also a binary star system. At magnitude 4.01, Gamma Trianguli completes the triangle. This is a blue-white subgiant star located about 112 lights years distant.

This constellation contains one Messier object. M33 is also known also as the Traingulum Galaxy and the Pinwheel Galaxy. It is a nearly face-on spiral galaxy located nearly three million light years from Earth. It is one of the most famous galaxies in the sky and is the largest member of the local group of galaxies which included the Andromeda Galaxy and our own Milky Way. There are many other dim galaxies in Triangulum, but they can only be seen with a large telescope.