COSMOS / CONSTELLATIONS / TRI
Triangulum (Triangle)
The Triangle. IAU abbreviation Tri. One of the 48 classical constellations listed by Ptolemy in the Almagest in the 2nd century AD.
STAR CHART
KEY FACTS
- IAU abbreviation
- Tri
- Latin name / genitive
- Triangulum / Trianguli
- Position
- Right ascension ≈ 2 h 12 m; declination +28° to +36°
- Visibility from Türkiye
- Visible in full from anywhere in Türkiye. When it crosses the meridian its centre stands about 82° above the horizon from Ankara.
- Best time to observe
- Best placed at 21:00 Türkiye time around 21 December.
- Number of stars
- 25 stars brighter than magnitude 6.5 in the catalogue; 5 brighter than 5 and 2 brighter than 4.
INTERACTIVE LAB
Where is Triangulum tonight?
The lab opens for Ankara on today’s date. Drag the time slider through the night; the “Best night” button jumps to the date when the constellation is highest at 21:00 (around 21 December). Change the city to compare the view from elsewhere in Türkiye and around the world.
MYTH, HISTORY AND OBSERVING
A small but distinctive triangle between Andromeda and Aries. The Triangulum Galaxy (M33), the third-largest member of the Local Group, is about 2.7 million light-years away and one of the most distant objects visible to the naked eye under very dark skies.
BRIGHTEST STARS
| Star | Magnitude | Distance (light-years) | Spectral type |
|---|---|---|---|
| β Tri | 3.00 | 127 | A5III |
| Mothallah | 3.42 | 63 | F6IV |
| γ Tri | 4.03 | 112 | A1Vnn |
| δ Tri | 4.84 | 35 | G0V |
| 6 Tri | 4.94 | 291 | F5V |
| 14 Tri | 5.15 | 433 | K5III |
| 7 Tri | 5.25 | 281 | A0V |
| 10 Tri | 5.29 | 377 | A2V |
Magnitude: apparent brightness; the smaller the number, the brighter the star. Distances derive from parallax measurements and are uncertain for distant stars. Source: HYG v4.1 star catalogue (CC BY-SA 4.0).
SOURCES
Position, visibility and best observing time were computed approximately for this page from the catalogue stars (Ankara, 39.9° N). The 88 constellations were adopted by the IAU in 1922; their boundaries were drawn by Eugène Delporte in 1930.