Constellations of the Month: December – Horologium:
We wrap up this year’s feature of constellations of the month, continuing December with the last constellation of this month, and the 88^th constellation: as the clock runs out on the year, finally with Horologium, “The Clock.”

Horologium constellation map courtesy of Openverse

Horologium, “The Clock” – The Horologium constellation is located in the southern hemisphere, and symbolizes and symbolizes “the clock.”  Horologium is a small and dim constellation that was established in the 18th century by the French astronomer Nicolas Louis de Lacaille. Initially, Lacaille referred to the constellation as Horologium Oscillitorium, meaning “the pendulum clock,” but it was subsequently abbreviated to just Horologium, which means “the clock.” The constellation lacks any associated myths and does not feature any prominent stars. It hosts the Horologium Supercluster, a significant supercluster that comprises approximately 5,000 groups of galaxies.

Barred Spiral Galaxy NGC 1512 in Many Wavelengths (2001)

Key points regarding Horologium:

• Meaning: The term “Horologium” translates to “The Clock” in Latin. The constellation Horologium lacks any stars that exceed a brightness of magnitude 3.00 and features only one star situated within 10 parsecs (32.6 light years) from Earth. The most luminous star in this constellation is Alpha Horologii, which has an apparent magnitude of 3.85. The closest star is Gliese 1061 (spectral class M5.5V), positioned at a distance of 12.04 light years from our planet. Horologium is home to three stars that have confirmed exoplanets: Iota Horologii (spectral class G0Vp), HD 27631 (G3IV), and WASP-120 (F5). It does not include any Messier objects. Additionally, there are no meteor showers linked to this constellation. Horologium does not feature any stars that have been formally named.
• Notable stars: Alpha Horologii is a bright giant star of spectral type K1III, with a visual magnitude of 3.86, making it the brightest star in the Horologium constellation. It is located about 117 light years from the Sun. R Horologii is the second brightest star in the constellation and is a red giant of type M7IIIe, roughly 100 light years away. Its apparent magnitude is 4.7, and it is classified as a Mira variable star, with a pulsation period of over 100 days and significant changes in brightness, ranging from 4.7 to 14.3. Beta Horologii, a giant star of type A4IIIm, is approximately 310 light years distant and has an apparent magnitude of 4.979. It is noted for being a chemically peculiar star with strong metal absorption lines. Delta Horologii is an A9V star with a visual magnitude of 4.93, located about 175 light years away. Iota Horologii, a yellow dwarf of type G0Vp, is about 56 light years distant and roughly twice as luminous as the Sun. A Jupiter-sized planet was discovered orbiting it in 1998. GJ 1061 is a red dwarf, classified as type M5.5V
• Other features: The Horologium Supercluster is a vast area in space, measuring about 550 million light years across, with parts located 700 million to 1.2 billion light years away from the Sun. It includes 5,000 galaxy groups, containing approximately 30,000 giant galaxies and 300,000 dwarf galaxies, and is also known as the Horologium-Reticulum Supercluster. NGC 1261 is a globular cluster with an apparent size of 12.9’ and is around 10.24 billion years old, primarily made of faint stars. It is located 53,500 light years from the Sun and was discovered by James Dunlop in 1826. Arp-Madore 1 is another globular cluster in Horologium, found 398,000 light years away, making it one of the farthest known globular clusters in the Milky Way’s halo. It has a size of 1.288’ by 0.691’ and a visual magnitude of 15.72. Other notable galaxies include NGC 1510, a lenticular galaxy 40 million light years away, and NGC 1483, a barred spiral galaxy also 40 million light years from Earth, both discovered in 1826. NGC 1433, another barred spiral, is notable for its double ring structure and distance of about 32 million light years. Lastly, NGC 1448 is an unbarred spiral galaxy 56.5 million light years away, where four supernovae have been observed, and evidence of a supermassive black hole has been found.
• Mythology: Lacaille designated Horologium in honor of the pendulum clock and its inventor, Christiaan Huygens. This constellation symbolizes the pendulum clock that Lacaille utilized to measure the duration of his observations. In various illustrations, the brightest star of the constellation, Alpha Horologii, is depicted as the pendulum, while in other representations, it signifies one of the weights.
• Visibility: Horologium is the 58^th largest constellation, covering 249 square degrees in the night sky. It is situated in the first quadrant of the southern hemisphere (SQ1) and is visible at latitudes ranging from +30° to -90°. The constellations that border it include Caelum, Dorado, Eridanus, Hydrus, and Reticulum. The name of the constellation, Horologium, is pronounced /ˌhɒrəˈlɒdʒiəm /. In English, it is referred to as the Clock. The genitive form of Horologium, which is used in the naming of stars, is Horologii (pronunciation: /ˌhɒrəˈloʊdʒiaɪ/). The three-letter abbreviation, which was established by the International Astronomical Union (IAU) in 1922, is Hor. Horologium is part of the Lacaille family of constellations, which also includes Antlia, Caelum, Circinus, Fornax, Mensa, Microscopium, Norma, Octans, Pictor, Reticulum, Sculptor, and Telescopium.

⁺‧₊☽◯☾₊‧⁺⋆⁺‧₊☽◯☾₊‧⁺⋆⁺‧₊☽◯☾₊‧⁺⋆⁺‧₊☽◯☾₊‧⁺⋆⁺‧₊☽◯☾₊‧⁺⋆⁺‧₊☽◯☾₊‧⁺⋆

Constellations:

Horologium courtesy of Openverse

Constellations of the Month:
December – Horologium

Material may be shared for personal and educational use, Share with family and friends. The material cannot be used in an educational setting whereby a “book fee” is charged in or above tuition costs, and the material here is being used without paying a licensing fee.. AI must file an application for use of such material.

You May Also Like. . .
NASA 1997 Liftoff Special	NASA Mission Patch Party

Constellations of the Month: Coming all 2025!