Fornax (“the furnace”) is an extremely faint southern sky constellation that was devised by French astronomer Nicolas Louis de Lacaille during the mid-18th century. The brightest star in this obscure constellation, Dalim, is a binary system found 46 light years from Earth with an apparent visual magnitude of +3.85.
Fornax is the 41st biggest constellation, and takes up an area of 398 square degrees of the southern celestial sphere. It is best viewed from November to January for observers located between +50° and -90° of latitude, with one way to locate the constellation being by finding Achenar, the brightest star in Eridanus, and following “the river” northwards to its first bend where Fornax will appear to its west. The constellations neighboring Fornax include Cetus, Eridanus, Phoenix and Sculptor.
Lacaille Constellation Family
Fornax is a member of the Lacaille family of constellations, together with Antlia, Caelum, Circinus, Horologium, Mensa, Microscopium, Norma, Octans, Pictor, Reticulum, Sculptor, and Telescopium.
French astronomer Nicolas Louis de Lacaille created the constellation following an expedition to South Africa in order to study the southern stars and constellations. In 1756, he subsequently introduced 14 new constellations, including Fornax Chemica (“the chemical furnace”), which in 1845 was later shortened to just Fornax.
– Dalim (Alpha Fornacis), the constellation’s brightest star, is a binary system situated 46 light years away that shines with an apparent magnitude of 3.85. The binary’s brightest component is a subgiant that has 33% more mass than the Sun, and four times more luminosity; while its companion star is believed to be a blue straggler with around 3/4 the Sun’s mass, and half its luminosity. The pair are separated by 56 AU, and have an orbital period of 269 years.
– Beta Fornacis, the second brightest star in Fornax, is a yellow-white giant around 173 light years from our solar system of magnitude 4.46. It is about 11 times bigger than our sun, with 1.53 times its mass, and 55 times its luminosity.
– Nu Fornacis, the constellation’s third brightest star, is a blue giant (B9.5III) found 371 light years away with an apparent magnitude of 4.69. It is around 3.2 times bigger than the Sun, with 3.65 times its mass, and 245 times its brightness. Being a variable star its brightness ranges from 4.68 and 4.73 over a 1.89 day period.
Other stars of interest in Fornax includes the binary star systems Epsilon Fornacis and Omega Fornacis; and the brown dwarf stars LP 944-20 and 2MASS 0243-2453. Six star systems have also been discovered containing planets, including Lambda2 Fornacis, HD 20868, WASP-72, HD 20781 and HD 20782.
Notable Deep-Sky Objects
While there are no Messier objects in Fornax, the constellation is home to a number of bright galaxies, including several that are contained within the Fornax Cluster, and can be seen using an 8 inch or larger telescope.
– Fornax Cluster is a rich concentration of galaxies found 62 million light-years away that is believed to contain around 58 large galaxies, as well as a number of smaller dwarf galaxies. As such, it is the second nearest and richest galaxy cluster to Earth, aside from the Virgo Cluster, and demonstrates the power of gravity to pull large groups of galaxies together and keep them gravitationally bound as a single entity. At the centre of the Fornax Cluster is NGC 1399, a large elliptical galaxy that contains up to 6,500 globular clusters, and its centre can be found a supermassive black hole which weighs the equivalent of 500 million suns.
Other objects of interest in the Fornax Cluster includes the elliptical galaxy NGC 1404; the lenticular galaxy Fornax A (NGC 1316); the spiral galaxy NGC 1350, whose arms form a pronounced central ring; and the Great Barred Spiral Galaxy (NGC 1365), shown in the image’s bottom right, which at 200,000 light years wide is one of the most prominent objects of its type in the entire night sky, and certainly the finest barred spiral galaxy in the southern hemisphere.
Outside of the Fornax Cluster, the constellation contains the galaxy UDFy-38135539, which is 13.1 billion light years away, making it one of the most distant object in the universe, with the most distant being GN-z11 found 13.39 light-years away in the constellation of Ursa Major. The constellation is also home to Fornax Dwarf (PGC 10074), an elliptical dwarf galaxy situated around 460 light years away that is a satellite of the Milky Way. It contains six globular clusters consisting of mostly old stars, the biggest of which is NGC 1049, although still very faint to observe with a visual magnitude of just +12.9.