At present, astronomy has adopted the division of the entire celestial sphere into 88 sections - constellations - with officially fixed boundaries. However, in the past, constellations were interpreted as collections of stars that stood out in the sky, which could be remembered according to certain outlines. At different times, they were given names associated with important concepts for people. The small southern constellation Compass is one of these kind of "monuments of the era."
How the Compass appeared in the sky
In ancient times, mythological characters were transferred to the sky, in the New Age, when astronomers were actively exploring the skies of the Southern Hemisphere, they tried to perpetuate the names of European monarchs or terms from everyday life that experienced the formation of science and technology on star maps. Far from all the fruits of these labors have survived to this day: for example, the constellation Electric Machine is now remembered only as a historical curiosity. But the groups of stars identified in the middle of the 18th century by a memberThe Paris Academy, professor of mathematics and astronomer N. Lacaille, was lucky, and among them the constellation Compass.
Legends dating back to antiquity, this constellation has no, but indirectly it is still connected with one mythological image that lived in heaven for a long time. The huge constellation Ship Argo, named after the legendary ship, appeared in Ptolemy's atlas of the 2nd century AD. e., and a group of dim stars located where the Argo mast was sometimes depicted in atlases, in 1754 on the map of Lacaille received the name Compass of the Navigator (in Latin - Pyxis Nautica). Two years later, Lacaille divided the Ship Argo into Stern, Kiel and Sails (they still exist) and proposed to single out the constellation Mast in place of the Compass, but history ordered otherwise, retaining, albeit in a truncated version, the original name - Compass (Pyxis, abbreviated as Pyx).
Location and description of the constellation
The area of the sky belonging to the Compass is small - only 221 square degrees. With the naked eye, you can see about two and a half dozen stars in it. Only eight of them are brighter than 5m and only two are brighter than 4m. The constellation Compass looks like an almost straight line formed by the three brightest stars - Alpha, Beta and Gamma. It is adjacent to the giant Hydra, as well as to the constellations of Sails, Pump and Stern.
In the Northern Hemisphere Compass can not be seen everywhere. In mid-latitudes, part of the constellation is visible at the very horizon in the south, while full visibilitypossible only south of 54° north latitude. The optimal time for observations falls mainly on the winter months - from January to March. In the photo, the constellation Compass appears to the eye as a scattering of rather dim stars.
Interesting stars
Alpha Compass is a class B hot blue giant with a surface temperature of over 24,000 K, 845-880 light-years away. It would be noticeably brighter if interstellar dust did not absorb some of its radiation. This star belongs to the short-period pulsating variables of the Beta Cephei type. The mass of Alpha Compass is more than 10 times, and the luminosity is 10,000 times higher than that of the Sun.
The most notable star in the constellation is the double T Compass, which belongs to the class of repeated novae. This system includes a white dwarf and a solar-type star. The last outbreak was registered in 2011. It is possible that the mass of the white dwarf is already close to the critical one, after which a supernova explosion will follow. Several thousand light-years away from us, T Compass is one of the closest supernova candidates to the Sun.
The constellation Compass contains several sun-like luminaries, as well as a red dwarf, around which the presence of exoplanets has been established. All these planets are gas giants, either too close to the parent star, or, conversely, too far away. Planets with a mass comparable to the Earth have not yet been discovered here.
Star clusters
Part of the sky related toto this constellation, includes a number of open star clusters. They can be observed with an amateur telescope. Such, for example, are the clusters NGC 2658 (located near Alpha Compass) and NGC 2627 in the region of the double star Zeta Compass.
Very spectacular open cluster NGC 2818. It is located in the southern part of the constellation, and more than 10,000 light-years away from us. This object is remarkable in that it contains a planetary nebula of a bizarre shape - the remnant of a gaseous shell thrown into space by a star that has ended its life. This beautiful planetary nebula was photographed in high resolution by the Hubble Space Telescope in 2008.
Extragalactic Attractions
From deep space objects in the constellation Compass, two galaxies are accessible to an amateur telescope (the diameter of the main mirror must be at least 200 mm): the elliptical NGC 2663 and the spiral NGC 2613, which is noticeably tilted "edge" in relation to the earth observer. The spiral arms of NGC 2613 can only be resolved by long-exposure imaging with a powerful telescope.
So, the modest constellation Compass - a legacy of the era of development of navigation in the southern oceans - does not shine with spectacular objects of high brightness, and in order to enjoy the joy of independently observing this section of the sky, appropriate conditions and the presence of a telescope are necessary. But even if the fan of astronomy does not have such opportunities, he has and will have morebeautiful images are produced using both powerful professional and amateur tools.
