Reticulum is a dim southern sky constellation that was one of 14 introduced in the 18th century by French astronomer Abbé Nicolas Louis de Lacaille. It is named after a “reticle” or the sighting device made of fine fibers found in the eyepiece of telescope, as well as other sighting instruments. The constellation’s brightest star is Alpha Reticuli, a yellow-giant located 250 light-years away that shines with a visual magnitude of 3.32.
Reticulum is the 82nd largest constellations, and can be seen by observers located between +23° and -90 of latitudes, although best seen from northern latitudes in January, and in the southern hemisphere from October to December. It can be found at a point mid-way between the bright stars of Canopus in Carina and Achenar in Eridanus, and is bordered by the constellations of Dorado, Horologium and Hydrus.
Lacaille Constellations family
Reticulum is a member of the Lacaille family of constellations, together with Antlia, Caelum, Circinus, Fornax, Horologium, Mensa, Microscopium, Norma, Octans, Pictor, Sculptor, and Telescopium.
The constellation Reticulum was introduced on a celestial globe published by German astronomer Isaac Habrecht II in 1621, although he named it Rhombus. In the 18th century, Nicolar Louis de Lacaille altered the constellation slightly and renamed it “le Réticule Rhomboide” to memorialize the reticle in the eyepiece of his telescope. It is this small apparatus that allows astronomers to measure the positions of the stars in the reticle’s cross hairs, and Nicolar Louis de Lacaille did just that during his stay at the Cape of Good Hope in the 1750s, having catalogued almost 10,000 southern stars over a two-year period. In 1763, the constellation was given the name Reticulum, which means “small net” in Latin, and in 1922 it was officially recognized by the International Astronomical Union (IAU).
– Alpha Reticuli, the constellation’s brightest star, is a yellow giant (G8 II-III) situated about 161.6 light-years distant with a visual magnitude of 3.315. It is thought to be around 300 million years old, and is around 13 times bigger than the Sun, 3 times more massive, and 240 times brighter. Alpha Reticuli also has a 12th magnitude companion, with both stars sharing a common proper motion.
– Beta Reticuli, the second brightest star in Reticulum, is a triple star system whose primary component is an orange giant that has a stellar classification of K0IV SB. Beta Reticuli is located about 100 light-years from our solar system, and has a visual magnitude of 3.84.
– Epsilon Reticuli, the constellation’s third brightest star, is a double star found 59.5 light years away that have a combined visual magnitude of 4.44. Its main component is an orange subgiant (K2 IV) star that is being orbited by a white dwarf.
Other stars of interest in Reticulum include the red giant Gamma Reticuli and Delta Reticuli; the orange stars Iota Reticuli and HD 27894; and the yellow stars Eta Reticuli, HD 25171, and HD 23127.
Notable Deep Sky Objects
While there are no Messier objects in Reticulum, it does contain some notable deep-sky objects.
– Topsy Turvy Galaxy (NGC 1313) is about 50,000 light years across and situated 15 million light years from Earth. This barred spiral galaxy is so-named because it has an uneven shape and an axis of rotation that is curiously not located at its centre. Its scattered apperance and strong starburst activity is believed to be the result of a galactic collision, although a lack of a nearby galaxy could indicate that it may have in fact swallowed a smaller companion.
– NGC 1559 is a barred spiral galaxy that is 50 million light years away, and shines with an apparent magnitude of 11. It is also classed as a Seyfert galaxy, meaning that it has an active galactic nuclei usually containing an extremely large black hole. Between 1984 and 2005 a total of three supernovae were seen in NGC 1559, namely SN 1984J, SN 1986L, and SN 2005df.