Triangulum
What is Triangulum?
Constellations· Autumn evenings (N) · small triangle between Andromeda and Aries. Exactly what its name says: a slim triangle wedged between Andromeda and Aries. Small, but famous for hosting M33, the Triangulum Galaxy, third largest of the Local Group. The Greeks saw the Nile delta or the island of Sicily in it. Zoom in below Mirach in the Sky view.
📍 Visible from where you are right now — computed in your browser
bearing · altitude · rise time · best time tonight
Where Triangulum is in your sky right now: https://nowsky.org/solar/sky?sel=con:Triangulum — location and time set automatically, no login.
Stars of the figure
| Star | Magnitude |
|---|---|
| Beta Trianguli | 3.0 |
| Mothallah | 3.4 |
| Gamma Trianguli | 4.0 |
The 3 brightest of the 3 stars used in the figure (3 lines). Lower magnitude means brighter.
Constellation basics
| Season | autumn evenings (N) |
|---|---|
| Brightest star | Beta Trianguli (3.0) |
| How to find | between Mirach and Hamal |
| Area rank | 88 |
Figures are representative approximations. Source: compiled from NASA and IAU public data.
Frequently asked
- When can I see Triangulum?
- autumn evenings (N).
- How do I find Triangulum?
- between Mirach and Hamal.
- What is the brightest star in Triangulum?
- Beta Trianguli, magnitude 3.
- Where is Triangulum in the sky right now?
- Open the sky view for your location and time and it shows the position in the sky right now.
In 1926 a distance measured in M33 settled what galaxies are
The Triangulum Galaxy M33 was one of the two specimens, with Andromeda, that Hubble used to settle the nature of galaxies. In 1926 he found 35 Cepheid variables in M33, measured its distance from their periods, and showed that this "nebula" was an independent island of stars hundreds of thousands of light-years (by the values of the day) beyond our galaxy. Being seen face-on, its arms could be resolved into individual stars, which was decisive.
The distance measured then was a third of today's value, but the conclusion stood. M33 is smaller and poorer in stars than Andromeda and therefore fainter, but its light is spread wide, and under a very dark sky it competes with Andromeda as the most distant object visible to the naked eye. The faint smudge beside the three stars of the thin triangle is the place where the universe was confirmed to be made of galaxies.
The constellation in depth
Triangulum is an ancient constellation from Ptolemy's list of 48; the Greeks called it Deltoton after the letter delta (Δ). Some saw the Nile delta in it, others the three-cornered island of Sicily. Thanks to its simple shape the name has barely changed in two thousand years.
The key object here is M33, the Triangulum Galaxy — a face-on spiral about 2.7 million light-years away and the third largest member of the Local Group after Andromeda and the Milky Way. Its low surface brightness makes it a naked-eye challenge reserved for very dark skies; binoculars show a soft smudge. 6 Trianguli is a pretty yellow-and-blue double star.
On October–December evenings look between Mirach in Andromeda and Hamal in Aries for the slim triangle of three 3rd-magnitude stars. It passes nearly overhead, so it is an easy target from Seoul. Turn on "More objects" in the Sky view to see where M33 lies.
Related
Figures are representative approximations. Simulated positions use J2000 mean elements.