Southern celestial hemisphere in the context of "History of astronomy"

In astronomy and navigation, the celestial sphere is an abstract sphere that has an arbitrarily large radius and is concentric to Earth. All objects in the sky can be conceived as being projected upon the inner surface of the celestial sphere, which may be centered on Earth or the observer. If centered on the observer, half of the sphere would resemble a hemispherical screen over the observing location.

The celestial sphere is a conceptual tool used in spherical astronomy to specify the position of an object in the sky without consideration of its linear distance from the observer. The celestial equator divides the celestial sphere into northern and southern hemispheres.

Fornax (/ˈfɔːrnæks/) is a constellation in the southern celestial hemisphere, partly ringed by the celestial river Eridanus. Its name is Latin for furnace. It was named by French astronomer Nicolas Louis de Lacaille in 1756. Fornax is one of the 88 modern constellations.

The three brightest stars—Alpha, Beta and Nu Fornacis—form a flattened triangle facing south. With an apparent magnitude of 3.91, Alpha Fornacis is the brightest star in Fornax. Six star systems have been found to have exoplanets. The Fornax Dwarf galaxy is a small faint satellite galaxy of the Milky Way. NGC 1316 is a relatively close radio galaxy.

Sagittarius is one of the constellations of the zodiac and is located in the Southern celestial hemisphere. It is one of the 48 constellations listed by the 2nd-century astronomer Ptolemy and remains one of the 88 modern constellations. Its old astronomical symbol is (♐︎). Its name is Latin for "archer". Sagittarius is commonly represented as a centaur drawing a bow. It lies between Scorpius and Ophiuchus to the west and Capricornus and Microscopium to the east.

The center of the Milky Way lies in the westernmost part of Sagittarius (see Sagittarius A).

Scorpius is a zodiac constellation located in the Southern celestial hemisphere, where it sits near the center of the Milky Way, between Libra to the west and Sagittarius to the east. Scorpius is an ancient constellation whose recognition predates Greek culture; it is one of the 48 constellations identified by the Greek astronomer Ptolemy in the second century.

Crater is a small constellation in the southern celestial hemisphere. Its name is the Latinization of the Greek krater, a type of cup used to water down wine. One of the 48 constellations listed by the second-century astronomer Ptolemy, it depicts a cup that has been associated with the god Apollo and is perched on the back of Hydra the water snake.

There is no star brighter than third magnitude in the constellation. Its two brightest stars, Delta Crateris of magnitude 3.56 and Alpha Crateris of magnitude 4.07, are ageing orange giant stars that are cooler and larger than the Sun. Beta Crateris is a binary star system composed of a white giant star and a white dwarf. Seven star systems have been found to host planets. A few notable galaxies, including Crater 2 and NGC 3981, and a famous quasar lie within the borders of the constellation.

PSR B1509−58 is a pulsar approximately at a distance of 17,000 light-years in the constellation of Circinus discovered by the Einstein X-Ray Observatory in 1982. Its diameter is only 12 miles (19 km). It is located in a Pulsar wind nebula created by itself, that was caused as a remnant of the Supernova (SNR) MSH 15−52 visual approximately 1,700 years ago at the southern celestial hemisphere not visible in the Northern Hemisphere. The nebula spans about 150 light years. The 0.1515 second pulsations ("6.597 times per second") are detected in the radio, X-ray, and γ-ray bands.

NASA described the star as "a rapidly spinning neutron star which is spewing energy out into the space around it to create complex and intriguing structures, including one that resembles a large cosmic hand". It is also known by the name "Hand of God". This phenomenon is called pareidolia.

The northern celestial hemisphere, also called the Northern Sky, is the northern half of the celestial sphere; that is, it lies north of the celestial equator. This arbitrary sphere appears to rotate westward around a polar axis due to Earth's rotation.

At any given time, the entire Northern Sky is visible from the geographic North Pole, while less of the hemisphere is visible the farther south the observer is located. The southern counterpart is the southern celestial hemisphere.