Reticulum (the Reticle) is a small, faint constellation in the southern sky, named after the fine network of lines used in telescope eyepieces and other optical instruments to measure positions accurately. Its modern form was introduced by French astronomer Nicolas-Louis de Lacaille in the 18th century, although an earlier constellation occupied the same region.
Its brightest star, Alpha Reticuli, now officially named Rhombus, is a yellow giant approximately 160 light-years away. Despite its modest size, Reticulum contains several interesting stars and galaxies, including the unusually shaped Topsy Turvy Galaxy.
Where Is Reticulum and When Can You See It?
Reticulum is the 82nd-largest of the 88 recognized constellations, occupying approximately 114 square degrees of the southern sky. It lies between Dorado, Horologium, and Hydrus.
The constellation is best observed during December and January, particularly from the Southern Hemisphere. It can be seen from tropical northern latitudes, but remains very low in the southern sky. One way to locate Reticulum is to look in the broad region between Canopus in Carina and Achernar in Eridanus.
Who Created the Reticulum Constellation?
The history of Reticulum begins before Lacaille. In the early 17th century, German astronomer Isaac Habrecht II depicted a constellation in this region called Rhombus, referring to its diamond-shaped pattern. During his observations at the Cape of Good Hope in the 1750s, Nicolas-Louis de Lacaille revised the constellation and named it le Réticule Rhomboïde, meaning the Rhomboidal Reticle.
A reticle is a set of fine lines or crosshairs placed within an optical instrument to help measure the position of an object. Such devices were particularly useful when astronomers needed to determine the precise positions of stars. The constellation’s name was subsequently Latinized to Reticulum, and it became one of the 88 constellations officially recognized by the International Astronomical Union.
Unlike ancient constellations, Reticulum has no traditional Greek or Roman mythology.
Notable Stars in Reticulum
- Rhombus (Alpha Reticuli) – The constellation’s brightest star, a yellow giant approximately 160 light-years away with an apparent magnitude of 3.3. It has expanded to more than 12 times the Sun’s radius. Its official name, adopted in 2024, recalls the earlier constellation Rhombus.
- Beta Reticuli – An evolved orange star approximately 100 light-years away, shining at magnitude 3.8. It is part of a multiple-star system.
- Epsilon Reticuli – An orange subgiant approximately 60 light-years away, with an apparent magnitude of 4.4. It hosts a giant exoplanet and has a distant white-dwarf companion, making it an interesting example of a planetary system associated with an evolved star.
- Gamma Reticuli – A red giant shining at approximately magnitude 4.5. Like other evolved giant stars, it has expanded and cooled after exhausting much of the hydrogen in its core.
- HD 23079 (Tupi) – A Sun-like star known to host a giant exoplanet. Its official name, Tupi, honors an Indigenous people of South America.
Deep-Sky Objects in Reticulum
Reticulum contains no Messier objects, but several of its galaxies are particularly interesting to astronomers studying star formation and galactic evolution.
NGC 1313 — The Topsy Turvy Galaxy
NGC 1313, commonly called the Topsy Turvy Galaxy, is a barred spiral galaxy approximately 15 million light-years away. It is roughly 50,000 light-years across and has a strikingly irregular appearance. Its spiral arms are uneven, with numerous bright blue regions where young stars are forming.
The galaxy also contains prominent clouds of glowing gas associated with intense star formation.
Its disturbed structure has prompted suggestions that it experienced a past interaction or merger, although the precise cause remains uncertain. Unlike many visibly distorted galaxies, NGC 1313 has no obvious nearby large companion responsible for its appearance.
NGC 1559 — A Galaxy with Multiple Supernovae
NGC 1559 is a barred spiral galaxy approximately 50 million light-years away, with an apparent magnitude around 11.Its bright spiral arms contain active star-forming regions, making it an important galaxy for studying the life cycles of massive stars.
Several supernovae have been observed in NGC 1559, including SN 1984J, SN 1986L, SN 2005df, and SN 2009ib. Supernova observations are particularly valuable because certain types can be used to estimate distances to galaxies and investigate the expansion of the universe.
How to Find Reticulum
Reticulum lies in a relatively quiet part of the southern sky, between Dorado, Horologium, and Hydrus. Its brightest stars form a small, roughly diamond-shaped pattern, but the constellation can be difficult to identify under suburban skies.
A detailed star chart is helpful for locating it. For telescope owners, NGC 1313 and NGC 1559 offer rewarding challenges, although both are considerably easier to photograph than to observe visually.