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Caput Trianguli, Metallah, Ras al Mothallah,
Alpha Trianguli, 2 Trianguli

Proper NamesMothallah, Caput Trianguli, Metallah, Ras al Mothallah
Bayer DesignationAlpha Trianguli
Flamsteed Number2 Trianguli
HR (BSC)544
Right Ascension1h 53m 5s
Declination+29° 34' 44"
Distance63 light years
19 parsecs
MagnitudeApparent: +3.4
Absolute: +2.0
Spectral ClassF5III bright yellow giant
Optimum VisibilityOctober / November
NotesMothallah is an ellipsoidal star, in which its rapid rate of rotation have caused it to flatten at the poles and expand at the equator. As the star shifts its orientation relative to Earth, it presents different aspects of this ellipsoidal form, causing its magnitude to vary over time. It possesses a small binary companion in a close and rapid orbit.

This orange subgiant, about 63 light years from Earth, takes its name from the Arabic al muthallath, meaning 'the Triangle' and, despite its 'Alpha' designation, is the second brightest star in the northern constellation of that name.

Imagery provided by Aladin sky atlas


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