Boötes

Located a little way to the south of the conspicuous pattern of stars forming the Plough is the constellation Boötes (the Herdsman), its leading star Arcturus very prominent in the northern spring night sky. Boötes is generally taken to depict a herdsman who is chasing the Great Bear around the northern sky. Indeed, the name of its leading star Arcturus is derived from the Greek title meaning ‘the Bear Watcher’. Early English mythology refers to Boötes as a Bear Driver, due to its proximity to Ursa Major (the Great Bear).

Arcturus - Bootes Finder Chart with BenetnashIn the event that you need help to locate Arcturus, first of all find the Plough, its familiar shape formed from the seven brightest stars in the constellation Ursa Major. For observers in or around mid-northern latitudes, the Plough is located at or near the overhead point at this time of year. Using the line of stars in the Plough handle as direction finders, follow their curve until you reach brilliant yellow-orange Arcturus, from where the rest of the stars in Boötes can be traced out (see below).

Although predominantly a northern constellation, portions of Boötes are visible from almost every inhabited part of the world and the whole of the constellation can be seen from South Africa and from most of Australia and South America, albeit fairly low down on the northern horizon.

BootesShining at magnitude –0.04 from a distance of 37 light years, Arcturus is the 4th brightest star in the entire sky.  One of its main claims to fame is that it was the first star to be observed in daylight, this feat being accomplished by the French astronomer Jean-Baptiste Morin in 1635. Brilliant Arcturus is the most prominent member of the Diamond of Virgo, an asterism formed from Arcturus, Spica in Virgo, Denebola in Leo and Cor Caroli in Canes Venatici, all four stars being depicted on the chart showing Spring Constellations.

Like Arcturus, Izar is a yellow-orange giant star, its light having taken around 200 years to reach us and the colour of which is fairly obvious in binoculars. Shining with an overall magnitude of 2.35, its name is derived from the Arabic ‘al-mi’zar’ meaning ‘the Girdle’, perhaps a fitting title in view of the fact that Izar is located near the middle of the constellation.

Slightly further away than Arcturus is magnitude 3.49 Nekkar, a yellow giant star which shines from a distance of around 225 light years. Another yellow star is Muphrid, named after the Arabic for ‘The Solitary Star of the Lancer’ and which shines at magnitude 2.68 from a distance of 37 light years. Chinese astronomers gave this star the rather grand name of Yew She Ti, meaning ‘The officer standing on the right of the Emperor’!

Boötes contains a number of double stars including Alkalurops which, shining from a distance of around 120 light years, has magnitude 4.5 and 6.7 components that are resolvable through binoculars. Located at a distance of around 95 light years, Iota is one of a tiny triangle of stars found just to the east of Benetnash, the end star in the handle of the Plough. This is another double worth checking out, the magnitude 4.8 and 6.7 components of Iota being far enough apart to be split either with good binoculars or a small telescope.

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