See Arcturus on the Night Sky this Week

Arcturus is the brightest star in the constellation of Bo�tes and the third brightest star on the night sky after Sirius and Canopus, bearing a visible magnitude of -0.05. It is often regarded as the sixth brightest star, behind Alpha Centauri, Vega and Capella, however it has been shown that Alpha Centauri is a binary star, while the other two are less brighter than Arcturus. This week, it will become visible on the night sky towards the eastern direction, about half way above the horizon.

To find the way to Arcturus, one only has to follow the arc of the handle of the Big Dipper; continuing on this path and you will find Spica, or alpha Virginis, therefore the saying "arc to Arcturus, then speed on to Spica".

Fast drift

Arcturus is a red star giant, located about 36,7 light years away in the Bo�tes constellation. Although having a mass of only 1.5 solar masses, Arcturus has a diameter of about 32 million kilometer, or 25 times the diameter of the Sun and a luminosity 115 that of the Sun and a surface temperature of only 4.300 Kelvin, while our star's surface temperature exceeds 6,000 Kelvin.

Most stars retain a relative fixed position on the sky. Arcturus, on the other hand, is moving at about 144 kilometer per second in the direction of the Virgo constellation. Over a period of 1,500 years, Arcturus travels an apparent distance on the sky equivalent to the apparent size of the Moon. This means that Arcturus is steadily approaching our solar system, and after 500,000 years it would have traveled 800 light years, rendering it invisible to the naked-eye.

According to calculations, the heat we receive from Arcturus is equivalent to the amount of energy radiated from a typical candle at a distance of about eight kilometers.

Bo�tes in mythology

Bo�tes means in Greek 'man herding cows', while in mythology, this is the name of the son of goddess Demeter, which was presumably awarded a place in the sky after inventing the plow. Other legends picture Bo�tes chasing Ursa Major with a large rod in his hand, while others often refer to Bo�tes as 'The Bear-guard'. Alternatively, Bo�tes is allegorically pictured as an upside down cone containing orange sherbet, because the star tends to display an orange hue.