Hvad er Arkturus ?

Arkturus er en stjerne i stjernebilledet Bjørnevogteren eller Bootes the herdsman.

Arkturus er en rødgul kæmpe med en diameter 22 gange solens og en lysstyrke på 100 gange mere.

Arkturus er en navigationsstjerne og er 37 lysår fra jorden



Find the three stars in the handle of the Big Dpper and then "arc to Arcturus" which is the bright star at the base of the constellation Bootes. The name Bootes means herdsman, while Arcturus means guardian of the bear.

Bootes looks somewhat like a kite, with Arcturus where the tail would be attached Just to its left is the Northern Crown, a little arc of stars said to have been formed when Dionysus tossed his crown into the heavens.

Here are some facts about Arcturus

It is only 37 light years away:
Its motion through space has carried it two moon diameters across the sky in the last 2000 years. It is 100 times as bright as the sun.
Its color is deep yellow because its temperature is about 4000K, compared to the sun's 5700K

Bootes, the herdsman.
Rides through the sky during the late Spring and early Summer. While he may have appeared as a shepherd to the ancients,
modern star-gazers like us can easily recognize the shape of a kite, with the bright star Arcturus at the point of the kite where the tail is attached.
Arcturus is a bright red supergiant star with a diameter nearly 20 times that of the Sun and a brightness more than 100 times that of our Sun. Since it is
only 36 light-years away (close for a star!),it appears as the brightest star in Bootes, and, in fact, the fourth brightest star in the sky.

The name Bootes is derived from the Sumerian Riv-but-sane, which means the "man who drove the cart". So Bootes was identified with a farmer who
plows the land during spring. The Romans called Bootes the Herdsman of the Septemtriones, that is, of the seven oxen represented by the seven stars of the Big Dipper, which was seen as the cart or the plow.

Bootes has a variety of myths and legends connected with it. One of the oldest says it represents the son of Zeus and a nymph, Callisto. Bootes was sent away and penniless by his brother. Left to pick his own fate, Bootes invented a plow which was pulled by oxen. He farmed the land and made a decent living. Callisto
was so pleased she convinced Zeus to place their son and his plow in the sky.Bootes was known as the female wolves by the Arabs, and the Hebrews called it the barking dog. Homer referred to Bootes in the Odyssey so it is an ancient constellation and may be one of the first recorded. In another early chart,
Bootes is shown running and holding a spear. He is accompanied by two hunting dogs, Asterion and Chara that form the constellation Canes Vanatici. Arcturus, the brightest star in the constellation has a great deal of information connected with it. it was known as the "Watcher" and by the Arabs and the "Keeper of the Heavens." To the Shawnee Indians of the southeast US, Arcturus represented a great hunter known as White Hawk.

For the Observer
Alpha Bootes, Arcturus ( 14h 16m +19° 11') is one of the oldest stars in the universe,a member of what astronomers refer to as Population II stars. These stars are have only traces of elements other than hydrogen and helium, indicating they were formed when there were few other elements available in the universe. With a magnitude of -0.1, Arcturus is the fourth brightest star in the sky. It is a giant yellow K2 class star,only 36 light years distant.

Epsilon Bootes, Izar, ( 14h 45m +27° 04') is a yellow K1 giant star that is also a binary.
It's magnitude is 2.4, and that of the companion is 2.7. The pair are 110 light years distant.

M3 (NGC5272) ( 13h 39m .9 +28° 38') is technically in Canes Venatici, but it is easier to find when referenced to the brighter stars of Bootes. M3 is a globular cluster containing about 44,500 stars. It is bright and easy to find in small telescopes.

M53 (NGC 5024) ( 13h 10m .5 +18° 26') like the above, does not technically belong to Bootes, but rather, Coma Berenices. Again, it is easier to find in reference with the brighter stars of Bootes. It is a rich globular cluster that is a nice sight in a small telescope.