The constellation Crux, the southern cross, is a constellation in the southern hemisphere of the sky. It is only visible from latitudes south of 27 degrees.
It is completely below the horizon in most parts of the northern hemisphere. It is the smallest constellation in the night sky with a total area of only 68 square degrees.
It is bordered by the constellations Centaurus on the east, north and west, and Musca to the south. Crux is one of the most familiar constellations in the southern hemisphere. It is an easy constellation to identify, due to its obvious cross shape and bright stars. Since the southern hemisphere does not have a bright star near its pole, Crux was used by sailors as a navigational aid. Although Crux is the smallest of the constellations it plays host to numerous objects of interest to the backyard astronomer, all of which are set against the wonderful backdrop of the Milky Way.
Three of the four main stars making up the Cross are obviously blue or blue—white in colour while the other, Gamma, has a definite orange—red tint. The brightest star in Crux is Acrux: the name appears to be a combination of the full Bayer reference for the star Alpha Crucis for more about star names see www. The name Acrux seems to have been first coined by the American astronomy writer and cartographer Elijah Hinsdale Burritt, in a star atlas he compiled in the s.
The fact that the stars of Crux were once part of the constellation Centaurus is alluded to by the 16th century Arabian astronomer Al Tizini, who defined the position of this star as being near the ankle of the right hind foot of the Centaur. Closer examination of Acrux with even a small telescope will show that it is in fact a double star with components of 1.
Beta Crucis is a magnitude 1. Binoculars will reveal both components of the orange—red double star Gamma Crucis, a magnitude 1. The association between these two stars is merely a line of sight effect, and they are not physically related: Gamma shines from a distance of 89 light years, roughly a quarter of the distance of the fainter star. Resolvable into individual stars even through binoculars, the splendid open star cluster NGC lies at a distance of around light years.
Also known as the Jewel Box, it contains over individual stars and can be spotted with the naked eye as a 4th magnitude, fuzzy, star-like object just to the south east of Beta Crucis, both objects lying within the same field of view of binoculars.
Crux certainly looks like an almost perfect small cross, perhaps marred to a slight degree by a dim, superfluous fifth star. Two of the main four stars, Acrux and Becrux, are of first-magnitude brightness. From top to bottom, Crux measures just 6 degrees — only a little taller than the distance between the pointer stars of the Big Dipper. Reminder: Your clenchd fist held at arm's length is 10 degrees wide. In fact, the Southern Cross is the smallest in area of all the constellations.
Like the Big Dipper of the northern sky, the Southern Cross indicates the location of the pole and as such is often utilized by navigators. The longer bar of the Cross points almost exactly toward the south pole of the sky, which some aviators and navigators have named the "south polar pit" because, unfortunately, it is not marked by any bright star.
It is believed that Amerigo Vespucci was the first European explorer to see the "Four Stars," as he called them, while on his third voyage in However, it can also be the 12th brightest star in the night sky, due to its variability in brightness. Acrux is a multiple star system. The primary star is a blue-white subgiant star located at around light-years away from the Sun, and the secondary star is a blue dwarf.
Both stars are hotter than the Sun, too, with Acrux A having a surface temperature of 24, K and Acrux B having a surface temperature of 28, K. Gacrux, also known as Gamma Crucis, is the third brightest star in the constellation of Crux, and the 25th brightest star in the night sky. It is located around It is also the nearest red giant to the solar system.
Imai is the fourth brightest star in the constellation of Crux. Designated as Delta Crucis, it is a blue-white subgiant star with an apparent magnitude of 2. It has a temperature of around 22, K. Designated Beta Crucis, Mimosa is the second brightest star in the constellation of Crux and the 20th brightest star in the night sky.
It has an apparent magnitude of 1. Mimosa is around 34, times brighter than our Sun. It is also quite a young star in comparison to others, having an estimated age between 8 to 11 million years.
Ginan, also known as Epsilon Crucis, is located around light-years away from Earth. It is the fifth brightest star in the constellation of Crux and has an apparent magnitude of 3. It is an orange-hued star that is times brighter than our Sun. It is evolving away from the main sequence and thus it will continuously expand. There are also many other stars in the Crux constellation. Four of them can be seen with the naked-eye.
Zeta Crucis is a binary star system that is located around light-years away from us. It is visible to the naked-eye and has an an apparent magnitude of 4. The primary star is a B-type main sequence star.
It is also cooler than our Sun. Theta Crucis is located around light-years away from us. It has an apparent magnitude of 4. It also has system consisting of a B-type main-sequence blueish-white star, as well as a Cephei variable star.
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