Deltoton

Triangulum in Dürer (1515) named "Deltoton".

WGSN star name "Deltoton", profile stickfigure, created by M. Sadegh Faghanpour (IAU WGSN).

Deltoton (Δελτωτόν; the letter Delta: Δ) is a modern star name for δ Tri (delta Trianguli) based on an ancient Greek name variant for the constellation Triangulum, probably the original one.

Etymology and History

"Delta" is the first letter in the ancient Greek term for "dios", the highest god who possesses and rules the stars. In early uranographies, this triangle was considered a sign of the divinity of the starry sky. The letter Delta was considered a divine inscription "written in the stars".

Mythology

The ancient Greek author Aratus (4th century BCE) starts his didactic poem with a dedication to the mighty god (Dios). Yet, he mentions the constellation "Triangulum" in a later verse.

WGSN star name "Deltoton", profile card, created by M. Sadegh Faghanpour (IAU WGSN).

IAU Working Group on Star Names

The name was discussed and approved by the IAU WGSN in 2025. The brightest stars in the constellation Triangulum were already named with Arabic names. WGSN chose to name δ Tri with this name because of the obvious pun.

δ Tri is a yellow dwarf star like our Sun but a bit smaller in mass and diameter. Only 35 light years away, it ranges among the nearest neighbours of the solar system. Therefore, it is the only star in the sky where we can directly see the propoer motion within the recent ~2000 years: Ptolemy describes δ Tri as ὁ μέσος αὐτῶν (the middle one of the three at the base of the triangle), as it was really in the middle between β and γ Tri. Yet, as of 2025, we find δ Tri closer to γ Tri (which would even count as "double star" in Ptolemy's terminology).

Reference

• References (general)
• References (early modern)