The southern sky , southern star (s) sky or southern starry sky is that half of the starry sky that lies south of the celestial equator and thus includes all points with negative declination (→ equatorial coordinate system ). From the South Pole , the southern sky can be seen entirely; the further north the observation site, the less it is visible.
When visibility is good, the southern sky comprises over 2,000 freely visible fixed stars ; when using binoculars, around 20,000 to 40,000. In large cities, even when the night sky is cloudless, you can only see around 100 to 500 stars, depending on the extent of air and light pollution . The brightest stars are all bigger than our sun . The brightest with an apparent magnitude of −1.5 mag is Sirius in the constellation of the Great Dog ; it has twice the solar radius and is 8 light years away. Also Canopus and the next 4 light years Star Toliman ( α Centauri ) are in the southern sky, but with approximately 60 ° south declination so close to the pole that both can not be observed from Central Europe.
The southern sky shows slightly more stars than the northern sky , as the center of the Milky Way is about 20 ° south of the equator in the constellation Sagittarius . Of the 14 brightest stars of the 1st magnitude (up to 1.0 mag), 7 each are in the north and south skies, 11 each of the 22 brightest (up to 1.5 mag).
The exact center of the southern sky is the elongated axis of the earth , the south celestial pole . The closest " Pole Star" Sigma Octantis (σ Oct), which is still clearly visible to him, is a 5th magnitude star and is only one twenty- fifth the brightness of Polaris , the Pole Star above the North Pole. Four of the brightest stars point more clearly to the position of the South Pole, from which they are 27-30 ° away: The stars Gacrux and Acrux in the Southern Cross point directly to the pole, while Alpha Centauri and Beta Centauri point almost at right angles to Gacrux . From low geographical latitudes in the southern hemisphere, they are best visible in autumn there.
In addition to the constellations Centaur , Southern Cross, Ship Argo and Scorpio , the two Magellanic Clouds , which are dwarf galaxies that accompany the galaxy (Milky Way), are also remarkable . At the transition to the northern sky over the celestial equator is the well-known constellation Orion . In the northern hemisphere it is in the south in winter , and therefore in the north in summer when viewed from the southern hemisphere.
While at the equator you can see exactly half of the southern and northern skies at any time of the year or night, in the higher southern latitudes of South Africa or Australia you can see around two thirds of the southern sky at any time, in southernmost South America more than 80 percent and it at the South Pole.
- Svend Laustsen, (et al.): Discoveries in the southern sky - an image atlas of the European Southern Observatory. Springer, Berlin 1987, ISBN 3-7643-1896-1
- David Ellyard, Wil Tirion: The Southern Sky Guide. Cambridge Univ. Press, Cambridge 2009, ISBN 978-0-521-71405-1