What it looks like
Triangulum is a small, ancient constellation whose three brightest stars form a long, narrow triangle. It sits between Andromeda and Aries, and despite its modest appearance contains M33, a face-on spiral galaxy that is the third-largest member of the Local Group after Andromeda and the Milky Way.
Brightest stars
Triangulum has three stars brighter than magnitude 4, forming its distinctive long triangle.
| Star | Magnitude | Distance | Meaning |
|---|---|---|---|
| Beta Trianguli | +3.00 | 127 ly | — |
| Mothallah (α Trianguli) | +3.41 | 63 ly | The Triangle |
| Gamma Trianguli | +4.01 | 118 ly | — |
Mythology and history
In Greek myth, Triangulum was associated with the delta of the Nile, with the island of Sicily, or with the letter delta — the shape of the Greek alphabet's fourth letter.
Delta, Nile and Sicily
Triangulum is one of the 48 constellations listed by Ptolemy, and it has been recognised as a triangle since at least Babylonian times. The Greeks associated it with the Greek letter delta (Δ) and with the triangular delta of the Nile. Another tradition linked it to Sicily, the triangular island sacred to Demeter and Persephone. In Roman times it was sometimes called Sicilia in honour of that island.
How to find it
Look between Andromeda and Aries on autumn evenings — the triangle is small but easy to spot once Andromeda is found.
- Find the Great Square of Pegasus, then look east for Andromeda, then for the triangle.
- The triangle is small and faint — use a chart if unsure.
- Best on autumn evenings from the northern hemisphere.
Key facts
- Abbreviation
- Tri
- Genitive
- Trianguli
- Meaning
- The Triangle
- Brightest star
- Beta Trianguli
- Main stars
- 3
- Area rank
- 78th
- Best visible
- December
- Declination
- +30°
- Meteor showers
- —
- Neighbours
- Andromeda, Pisces, Aries, Perseus
Deep-sky objects
The Triangulum Galaxy (M33) is a face-on spiral galaxy about 2.7 million light-years away and the third-largest member of the Local Group. It is visible to the naked eye under very dark skies, making it one of the most distant objects visible without a telescope.
Frequently asked questions
What does the constellation Triangulum look like?
Triangulum is a small northern constellation named for its simple triangle shape, home to the Triangulum Galaxy (M33), the third-largest galaxy in the Local Group.
What is the brightest star in Triangulum?
The brightest star in Triangulum is Beta Trianguli, shining at around magnitude 3.00.
When is Triangulum best visible?
Triangulum is best seen from both hemispheres during December.
What is the story behind Triangulum?
In Greek myth, Triangulum was associated with the delta of the Nile, with the island of Sicily, or with the letter delta — the shape of the Greek alphabet's fourth letter.
Which constellations are near Triangulum?
Triangulum borders Andromeda, Pisces, Aries and Perseus.
Andromeda
Aries