Right Ascension:

2 hours


30 degrees

Area in Square Degrees:


Crosses Meridian:

9 PM, December 5

Visible Between Latitudes:

90 and -50 degrees

The constellation Triangulum, the triangle, is completely visible at 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 below © Sea and Sky
Triangulum constellation map
Triangulum constellation map
© Torsten Bronger CC BY-SA 3.0
Name / Meaning
Object Type
V Mag
1 2 3 4 5
Beta Trianguli
Gamma Trianguli
Delta Trianguli
Triangulum Galaxy
"Head of the Triangle"
Spiral Galaxy
Binary Star System
Binary Star System
Blue-White Subgiant Star
Binary Star System

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.

Triangulum contains one Messier object called M33, also known also as the Traingulum Galaxy and the Pinwheel Galaxy. It is a nearly face-on spiral galaxy located about 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 includes the Andromeda Galaxy and our own Milky Way. There are many other faint objects in Triangulum, but they can only be seen with a large telescope. These include an emission nebula known as NGC 604 and a spiral galaxy called NGC 634.

ESO image of M33, the Triangulum Galaxy
ESO image of M33, the Triangulum Galaxy
© European Southern Observatory / CC BY 4.0
Image of Emission nebula NGC 604 in Triangulum
Emission nebula NGC 604 in Triangulum
© Judy Schmidt / CC BY 2.0
Hubble image of Spiral galaxy NGC 634
Hubble image of Spiral galaxy NGC 634
© ESA/Hubble & NASA / CC BY 3.0