Horologium Constellation

Horologium constellation lies in the southern sky. Its name means “the clock” in Latin.

It is a small, faint constellation that was created in the 18th century by the French astronomer Nicolas Louis de Lacaille. Lacaille originally named the constellation Horologium Oscillitorium, or “the pendulum clock,” but the name was later shortened to simply Horologium, “the clock.”

The constellation is not associated with any myths and does not have any bright stars. It is home to the Horologium Supercluster, a massive supercluster containing some 5,000 galaxy groups.


horologium constellation,horologium star chart,horologium star map

Horologium Constellation Map, by IAU and Sky&Telescope magazine

Horologium is the 58th constellation in size, occupying an area of 249 square degrees in the night sky.

It is located in the first quadrant of the southern hemisphere (SQ1) and can be seen at latitudes between +30° and -90°.

The neighboring constellations are Caelum, Dorado, Eridanus, Hydrus and Reticulum.

Horologium has one star with known planets and contains no Messier objects. The brightest star in the constellation is Alpha Horologii, with an apparent visual magnitude of 3.85. There are no meteor showers associated with the constellation.

Horologium belongs to the Lacaille family of constellations, along with Antlia, Caelum, Circinus, Fornax, Mensa, Microscopium, Norma, Octans, Pictor, Reticulum, Sculptor, and Telescopium.


Lacaille named the constellation after the pendulum clock to honour its inventor Christiaan Huygens.

The constellation represents the pendulum clock Lacaille used to time his observations.

The brightest star in the constellation, Alpha Horologii, represents the pendulum in some depictions, and is located on one of the weights in others.


α Horologii (Alpha Horologii)

Alpha Horologii is a giant of the spectral type K1III. It has a visual magnitude of 3.86 and is the brightest star in Horologium. It is approximately 117 light years distant from the Sun.

R Horologii (HD 18242)

R Horologii is the second brightest star in the constellation. It is a red giant of the spectral type M7IIIe, approximately 100 light years distant from Earth. It has an apparent visual magnitude of 4.7.

R Horologii is classified as a Mira variable, which means that it is a pulsating variable red star with a pulsation period over 100 days and a light amplitude over one magnitude in infrared and 2.5 magnitude in visual.

The star has a period of 407.6 days and its variations in brightness range from 4.7 to 14.3, which is one of the largest magnitude ranges known.

β Horologii (Beta Horologii)

Beta Horologii is a giant star belonging to the spectral class A4IIIm, approximately 310 light years distant. It is a chemically peculiar star of the metallic-line type, with strong absorption lines of metals. It has an apparent visual magnitude of 4.979 and is the third brightest star in the constellation.

δ Horologii (Delta Horologii)

Delta Horologii belongs to the spectral class A9V. It has a visual magnitude of 4.93 and is approximately 175 light years distant.

ι Horologii (Iota Horologii)

Iota Horologii is a yellow dwarf of the spectral type G0Vp, about 56 light years distant. It has a visual magnitude of 5.40. It is about twice as luminous as the Sun.

An extrasolar planet the size of Jupiter was discovered orbiting the star in a near Earth orbit in 1998. NASA ranked the star 69th on the list of candidates for the Terrestrial Planet Finder mission before the project was abandoned.

GJ 1061

GJ 1061 is a red dwarf of the spectral type M5.5V, only 11.99 light years distant from Earth. It has a visual magnitude of 13.03.

The star has only 11.3% of the Sun’s mass and is 0.1% as luminous. It is the 20th nearest known star system to the Sun.


horologium supercluster

Horologium Supercluster map, source: Richard Powell, Atlas of the Universe

Horologium Supercluster

The Horologium Supercluster is a massive supercluster some 550 million light years across and covering an area of 12°x12°.

The nearest part is approximately 700 million light years distant from the Sun, and the farthest is about 1.2 billion light years away.

The supercluster contains about 5,000 galaxy groups, which include 30,000 giant galaxies and 300,000 dwarf galaxies.

It is also called the Horologium-Reticulum Supercluster.

globular cluster,horologium constellation

NGC 1261 – Based on observations made with the NASA & ESA Hubble Space Telescope, and obtained from the Hubble Legacy Archive, which is a collaboration between the Space Telescope Science Institute, the Space Telescope European Coordinating Facility and the Canadian Astronomy Data Centre.

NGC 1261

NGC 1261 is a globular cluster.

It was discovered by the Scottish astronomer James Dunlop in 1826.

The cluster has a visual magnitude of 8.3 and is 53,500 light years distant from the Sun.

It is a well condensed cluster composed mainly of very faint stars.


AM1 is a globular cluster in Horologium.

At a distance of 398,000 light years, it is the most remote globular cluster known in the Milky Way Galaxy.

NGC 1512

barred spiral galaxy.spiral galaxy in horologium

NGC 1512, image: NASA, D. Maoz, A. J. Barth, L. C. Ho, A. Sternberg and A. V. Filippenko.

NGC 1512 is a barred spiral galaxy in Horologium.

It is 8.9’x5.6′ in size and 70,000 light years across, almost as large as the Milky Way.

The galaxy is particularly notable for its starburst ring, composed of young clusters and extending about 2400 light years across.

It has an apparent magnitude of 11.1, which makes it bright enough to be observed in amateur telescopes.

The galaxy is about 30 million light years distant from the solar system.

NGC 1512 and NGC 1510 – In this image, the wide ultraviolet eyes of NASA’s Galaxy Evolution Explorer show spiral galaxy NGC 1512 sitting slightly northwest of elliptical galaxy NGC 1510. The two galaxies are currently separated by a mere 68,000 light-years, leading many astronomers to suspect that a close encounter is currently in progress. The overlapping of two tightly wound spiral arm segments makes up the light blue inner ring of NGC 1512. Meanwhile, the galaxy’s outer spiral arm is being distorted by strong gravitational interactions with NGC 1510. Image: NASA, JPL-Caltech