α Boötis

Arcturus, alpha Boötis, is a golden giant, about twenty times the size of the Sun. It's also a binary; with its companion it has a combined visual magnitude of -0.05, making it the fourth brightest in the skies. In fact, it's the brightest star in the northern hemishere.

Arcturus is a variant of its Greek name meaning the Guardian of the Bear (that is, the Great Bear of the North -- Ursa Major). In fact in Greek ‘bear’ and ‘arctic’ are similar: αρκτoς (arktos) and αρκτικoς (arktikos).

A Spring and Summer star, it's found east of Leo and directly below the handle of the Big Dipper.


In the same field, very near Arcturus, is the telescopic binary Struve 1825: 6.5, 8.4; PA 154º, 4.2" . The primary is a pale yellow, the companion whitish.

West of Arcturus a little over a binocular field you'll find an arrow-shaped asterism, easily seen with the naked eye: three stars which form the left foot of Boötes the Hunter - top to bottom: eta, tau and upsilon.

Directly south of Arcturus, a little over two binocular fields, is the attractive telescopic binary Struve 1835: 5.0, 6.8; 194º, 6.0". It is the northern most star in a group of three, as well as the brightest.

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