Around mid-evening in late May, relish your time under the spring stars. Gorgeous Arcturus is bright and beautiful, gleaming high in the southeast about 9 p.m. and due south about 11 p.m. Look high and you will see this orange wonder, the brightest star in the constellation Bootes the Herdsman.
Around mid-evening in late May, relish your time under the spring stars. Gorgeous Arcturus is bright and beautiful, gleaming high in the southeast about 9 p.m. and due south about 11 p.m. Look high and you will see this orange wonder, the brightest star in the constellation Bootes the Herdsman. Otherwise known as Alpha Bootis, Arcturus is the third brightest star of the night sky. It is one of three bright stars that partition the sky roughly into thirds. The other two are also visible in late May evenings. Vega, which dominates the summer evening sky, shines low in the northeast about 9 p.m. in late May. This star appears blue-white and is the lucida (the brightest star) of the compact constellation Lyra the Lyre. Swing around northwest and what do you see? Probably a neighbor’s house or hill, but if you are fortunate to be able to observe with a wide-open sky, you will find Capella. This yellow beacon is the highest of the many bright stars in winter’s evening skies. The autumn has no brilliant star high up in the southern sky as seen from the northern hemisphere, but a bright blue-white star, Fomalhaut, rules low in the south every fall. Arcturus has a fascinating history. It is called the “Bear Watcher,” as it follows the Big Bear (Ursa Major) -- which contains the Big Dipper and the Little Bear (Ursa Minor), otherwise known as the Little Dipper, around the pole. Opened the World’s Fair Only 37 light years away, the light you see tonight from Arcturus left the star in 1971. Its light was used to open the 1933 Century of Progress International Exposition at the World’s Fair in Chicago. That light had left Arcturus about the time of the previous Chicago fair in 1893. The rays were focused on photo-electric cells in a series of astronomical observatories and then transformed into electrical energy that was transmitted to Chicago. The starlight was used to activate the lights of the fair. Stars are classified by their temperature, which equates to its color. Arcturus is a classic “K” star with a temperature of 4290 degrees Kelvin. The star actually shines 113 times more brightly than our sun, if you were able to compare them side by side. It is much cooler than our sun, allowing it to radiate a great deal more energy in the infrared, which is invisible to the human eye. If your eyes could see infrared, Arcturus would glow 215 times brighter than the sun’s infrared output. And Arcturus has a diameter 26 times that of the sun. It is moving across the sky at much greater velocity than other bright stars, and given its movement and composition, astronomers have suspected the star may be passing through, possibly being ejected from another galaxy. Sir Edmond Halley, the famed English astronomer (1656-1742) who determined the orbit of Halley’s Comet, was the first to notice the movement of Arcturus, as seen in a telescope from year to year. It might have been the first star to be seen by telescope in broad daylight, having been spotted by Jean-Baptists Morin de Villefranche in 1635. Following a curving arc from the Big Dipper’s handle leads one straight to Arcturus. Keep tracing that curving arc past Arcturus, and you will find the bright blue-white star Spica, lower in the southeast in late May evenings. The constellation Bootes looks very much like a huge kite, with Arcturus at the bottom where the tail would be attached. In the Bible The King James version of the Bible mentions Arcturus twice, both times in the Book of Job: "Which maketh Arcturus, Orion, and Pleiades, and the chambers of the south." -- Job 9:9. "Canst thou bring forth Mazzaroth in his season? or canst thou guide Arcturus with his sons?" -- Job 38:32. “Mazzaroth” may refer to constellations, and both these passages refer to the power of God. Last-quarter moon is May 27 and rises about 1 a.m., giving dark, star-lit evening skies. That assumes light pollution isn’t much of a problem! Keep looking up! Peter W. Becker is managing editor at The Wayne Independent in Honesdale, Pa. He has been an amateur astronomer since the age of 12, in 1969. He may be reached at firstname.lastname@example.org.