Arcturus (Ἀρκτοῦρος)

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Arcturus is a reddish star, yet it twinkles in many colours - even when high above the horizon and in a rather dark landscape.

Arcturus in twilight (CC BY Paolo Palma 2025). Single shots with Nikon coolpix p510 taken on 12 november 2025 from about 150 metres of distance. Walls of Santo Stefano, a 9th-century church, built on the ruins of a 2nd-century Roman villa. It located in the municipality of Anguillara Sabazia, near Rome, in Italy.

Arcturus (Ἀρκτοῦρος), The Guard, is a modern star name adopted by the International Astronomical Union in the IAU-Catalog of Star Names (IAU-CSN). Its origin is Greek. It is the name of HIP 69673 (α Boo, HR 5340) in constellation Boo.

Etymology and History

The ancient Greek name unambiguously means "The Guard". He is depicted in the shepherd of Bootes whose main star this is, and who was called The Ploughman in ancient Greek. In Roman times, it made sense to connect the guard to the seven oxen seen in the Big Dipper, or - in the Egyptian part of the empire - as the hippo goddess guarding the bull's thigh.

Spelling Variants

• Arkturus, Arkturos (closer to the Greek original)

Folk Etymology

Since Early Modern times, popularly connected to the Greek word Άρκτος, "bear", which also came to mean "north". Then, meaning can ambiguously be "Guardian of the North" and "Guardian of the Bear", referring to the nearby constellation Ursa Major.

Image Gallery

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  Arcturus in twilight (CC BY Paolo Palma 2025). Single shots with Nikon coolpix p510 taken on 12 november 2025 from about 150 metres of distance. Walls of Santo Stefano, a 9th-century church, built on the ruins of a 2nd-century Roman villa. It located in the municipality of Anguillara Sabazia, near Rome, in Italy.

• 

  Arcturus in twilight (CC BY Paolo Palma 2025). Single shots with Nikon coolpix p510 taken on 12 november 2025 from about 150 metres of distance. Walls of Santo Stefano, a 9th-century church, built on the ruins of a 2nd-century Roman villa. It located in the municipality of Anguillara Sabazia, near Rome, in Italy.

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  Optical image of Arcturus provided via the Mikulski Archive for Space Telescopes (MAST), STScI, and NASA.

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  Arcturus in Bootes. Image created using the Aladin Sky Atlas software from the Strasbourg Astronomical Data Center and DSS (Digitized Sky Survey) data. DSS is one of the programs of STScI (Space Telescope Science Institute) whose files are in the public domain ( http://archive.stsci.edu/data_use.html )

IAU Working Group on Star Names

The name was adopted by the IAU WGSN on 2016/06/30.

Weblinks

• Website of the IAU WGSN: https://exopla.net/

Reference

• References (general)
• References (early modern)[