Octans

Octans is a faint constellation located in the deep Southern Sky. Its name is Latin for the eighth part of a circle. The constellation is named after the octant, which is a navigational instrument. This group of stars is quite important to astronomers. It contains the location of the south celestial pole. This is the point in the sky that marks the southern axis of Earth.

This constellation was created by the French astronomer Nicolas Louis de Lacaille. He developed it during an expedition to the Cape of Good Hope. In 1752, he named it l'Octans de Reflexion, or the reflecting octant. Lacaille spent two years at the Cape of Good Hope. During this time, he observed and catalogued almost 10,000 southern stars. He created fourteen new constellations to fill uncharted regions of the Southern Celestial Hemisphere. These regions were not visible from Europe. Most of his new constellations honored instruments from the Age of Enlightenment. His catalogue, Coelum Australe Stelliferum, was published in 1763 after his death. In Europe, the constellation became known as Octans Hadleianus. This name honored the English mathematician John Hadley, who invented the octant in 1730.

Octans is a generally inconspicuous constellation. It has only one star that is brighter than magnitude 4. This magnitude scale measures how bright a star appears from Earth. The brightest member of the constellation is Nu Octantis. This is unusual because it has a very late Bayer designation. Nu Octantis is a K1 IV subgiant star. This means it is a star that has begun to expand. It has a white dwarf companion star. This system is also orbited by one exoplanet.

Other stars in the constellation serve specific roles in astronomy. Beta Octantis is the second brightest star in the group. Sigma Octantis is known as Polaris Australis, or the southern pole star. It has a magnitude of 5.4. This star sits just over 1 degree away from the true south celestial pole. Because it is faint, it is not practical for navigation. BQ Octantis is even fainter, with a magnitude of 6.82. It is located much closer to the South Pole than Sigma Octantis. Interestingly, Octans also contains the southern pole star of the planet Saturn. That star is Delta Octantis, which has a magnitude of 4.3.

Astronomers have discovered several star systems with planets within Octans. At least four such systems are known to exist. Mu2 Octantis is a binary star system. The brighter star in this system has a planet. Nu Octantis A also has a planet orbiting it. The system HD 142022 is another binary system. One component is a sunlike star with a massive planet. This planet has an orbital period of 1928 plus or minus 46 days. The star HD 212301 is a yellow-white main sequence star. It is orbited by a hot Jupiter. This large planet completes a full orbit every 2.2 days.

Beyond individual stars, Octans contains massive deep-sky objects. These objects are very far away from our solar system. NGC 2573 is a faint barred spiral galaxy. This galaxy is the closest NGC object to the south celestial pole.

There are also two other barred spiral galaxies in this area. NGC 7095 is located 115 million light-years from Earth. NGC 7098 is located 95 million light-years away.

You can also find a sparse open cluster called Collinder 411 in the constellation.

Because Octans is so far south, it has very little mythology. It is a relatively recent addition to our maps of the sky. Most ancient cultures did not live far enough south to see it. This makes it different from older constellations like Orion. Instead of ancient stories, Octans represents the scientific progress of the 18th century. It connects the study of the stars to the history of human navigation. By studying this faint area, astronomers learn about the poles of our own planet and others. It remains a vital part of the 88 modern constellations used by scientists today.