The Constellation Triangulum

by Dominic Ford
Triangulum Triangulum
The constellation Triangulum. Roll mouse over to see labels.
Source: Stellarium.

Triangulum is a small yet ancient northern constellation, nestling between Andromeda and Aries. It appears highest in the evening sky in the months around October.

Comprising simply of a triangle of two third magnitude stars and one fourth magnitude star, it is far from conspicuous. In ancient Greece it was known as ‘Deltoton’ because it resembled a capital delta (Δ).

Although it is home to only one bright deep sky object, it is a significant one. The Triangulum Galaxy (M33) is a member of the Local Group of galaxies, and the second-closest galaxy of comparable size to our own.

M33 is a spiral galaxy like our own, and orientated in an almost face-on orientation so that its spiral structure is finely displayed. However, this also means its light is spread over a large sky area, comparable in size to the full moon. The slightest light pollution makes it quite impossible to make out its diffuse light.

Date First Appeared
Sky Area
0.3% of the sky
131.8 square degrees
Messier Objects
Triangulum contains the following Messier object: M33.
Caldwell Objects
Triangulum contains no Caldwell objects
The following constellations neighbor Triangulum: Andromeda, Aries, Perseus, Pisces.
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Brightest Objects in Triangulum

Stars Open Clusters Globular Clusters Galaxies
Stars Open Clusters Globular Clusters Galaxies
β-Tri (mag 3.0) IC 1800 Messier 33 (mag 5.7)
Mothallah (mag 3.4) NGC 925 (mag 10.0)
γ-Tri (mag 4.0) NGC 672 (mag 10.8)
δ-Tri (mag 4.9) IC 1727 (mag 11.6)
14-Tri (mag 5.2) NGC 784 (mag 11.8)
HD 63697 (mag 5.2) NGC 949 (mag 11.9)
7-Tri (mag 5.2) NGC 890 (mag 12.0)
10-Tri (mag 5.3) NGC 777 (mag 12.0)
12-Tri (mag 5.3) NGC 670 (mag 12.1)
15-Tri (mag 5.4) NGC 736 (mag 12.2)
ε-Tri (mag 5.5) NGC 750 (mag 12.2)
11-Tri (mag 5.6) NGC 751 (mag 12.5)
HD 10390 (mag 5.6) NGC 783 (mag 13.0)
HD 11007 (mag 5.8) NGC 582 (mag 13.0)
HD 15755 (mag 5.8) NGC 661 (mag 13.0)
HD 11928 (mag 5.9) NGC 855 (mag 13.0)
13-Tri (mag 5.9) NGC 688 (mag 13.0)
HD 10348 (mag 6.0) NGC 969 (mag 13.0)
5-Tri (mag 6.2) NGC 973 (mag 13.0)
TZ Tri (mag 6.6) NGC 987 (mag 13.0)
R Tri (mag 7.3) NGC 1060 (mag 13.0)
χ-Tri (mag 9.0) NGC 587 (mag 13.0)
HD 285876 (mag 11.3) NGC 666 (mag 13.0)
HD NGC 940 (mag 13.0)
HD NGC 959 (mag 13.0)




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