Corona Borealis
- Hercules
- Bootes
- Snake (head)
The Northern Crown, in the jargon Corona Borealis ( from Latin ) is a constellation north of the celestial equator.
Description
The Northern Crown is a relatively small but distinctive constellation between Hercules and Bootes. Your stars form a semicircle. The brightest star Gemma (Latin for gem) is striking bright with 2.22 m, the other stars only reach about fourth magnitude.
The constellation contains two interesting variable stars, R Coronae Borealis and T, which exhibit strong variations in brightness.
In the Northern crown featuring an expansive galaxy cluster Abell 2065, containing about 400 galaxies. Because of the great distance, however, the galaxies only reach the 16th magnitude and therefore are visible only in large telescopes or long-exposure photographs. The rich cluster of galaxies Abell 2142 is about 1.2 billion light-years away and also no galaxy brighter than 16 may contain, is an interesting research object, because in it the fusion of two such clusters can be observed. It is located in the southeastern region of the constellation near ε Coronae Borealis.
History
The Northern Crown is one of the 48 constellations of the ancient astronomy, which have already been mentioned by Ptolemy. Its counterpart in the sky, the Southern Crown ( Corona Australis ).
Presented for the ancient Greeks, the constellation a crown dar. In other cultures, it had different meanings. So the Arabs saw it as the bowl of a beggar, the Chinese have a money chain and the Celts a rapidly rotating wheel or lock.
Mythology
According to Greek mythology, the Northern Crown was the jeweled crown of Ariadne, daughter of King Minos of Crete. With Ariadne Help the hero Theseus defeated the Minotaur. Theseus received from her a thread with which he found his way out of the labyrinth in which the monster was confined.
In Celtic mythology, the Northern Crown ( Caer Arianrohd ) was the wheel (or the castle ) of Arianrhod.
Celestial objects
Stars
The brightest star, α Coronae Borealis is about 80 light-years from the Sun. He is a bluish - white star of spectral type A0. All 17.36 days reduces its brightness by only 0.1 magnitudes. Caused the blackout by a fainter companion star, which passes in front of the main star. Such stars are called eclipsing binaries. The star belongs to the so-called "bear power ", a nearby open clusters.
α Coronae Borealis is also called Gemma (Latin for "Gem " ) or Alphekka. The latter name is ancient Arabic origin and could be derived from al - fakkah ( the Broken ). This refers to a "broken ring " of stars ( the constellation of the Northern Crown).
ρ Coronae Borealis is a Sun-like yellow dwarf star of spectral type G0 V in 55 light years away. He is somewhat more luminous than our Sun and about 10 billion years, about twice as old. 1997, in which an exoplanet star and a circumstellar disk, similar to the Kuiper belt was discovered.
Double stars
The system η Coronae Borealis is 59 light years away. Two yellowish luminous stars of spectral types G1 and G3 move in only 41.5 years around a common center of gravity. Seen from Earth, the star at a distance of 0.7 ( 2000 ) to 0.4 ( 2020 ) arc seconds. To separate them you need a mid- telescope of 15 cm aperture.
The 200 light years distant system γ Coronae Borealis consists of two bluish- white stars of spectral types A0 and A3.
The system ζ Coronae Borealis is 450 light years away and consists of two equally bright stars of spectral type A2.
Due to the larger angular distance of 6.3 arcsec and 7, both systems can be resolved with a smaller telescope in single stars.
Variable Stars
R Coronae Borealis is the namesake a group of variable stars, irregularly change their brightness. For stars of this type, one can observe a rapid drop in brightness. After a period of time can not be predetermined brightness is slowly increasing again. In studies of the spectrum of this star was found that its surface contains relatively large amount of helium and carbon. It is believed that the stars repel at irregular intervals parts of their outer gaseous envelope. The carbon molecules condense from opaque to soot particles. The dust cloud dissipates with time and the star appears brighter again. R Coronae Borealis has a brightness of 5.7 m at maximum and can just be seen with the naked eye yet. At a minimum, the brightness drops to 14.8 m and the star can only be observed in a larger telescope.
T Coronae Borealis is a variable star of type recurrent nova. With a brightness of 10.8 m, it is very faint, but was up to 2.0 m conspicuously highlighted during outbreaks in 1866 and 1946
Messier and NGC objects
The Northern Crown contains no brighter star clusters, nebulae or galaxies that were included in the Messier catalog, or NGC.