Horologium (constellation)
| Constellation | |
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| Abbreviation | Hor |
|---|---|
| Genitive | Horologii |
| Pronunciation |
/ˌhɒrəˈloʊdʒiəm, -ˈlɒ-/, genitive /ˌhɒrəˈloʊdʒiˌaɪ, -ˈlɒ-/ |
| Symbolism | the Pendulum Clock |
| Right ascension | 3 |
| Declination | −60 |
| Family | La Caille |
| Quadrant | SQ1 |
| Area | 249 sq. deg. (58th) |
| Main stars | 6 |
|
Bayer/Flamsteed stars |
10 |
| Stars with planets | 3 |
| Stars brighter than 3.00m | 0 |
| Stars within 10.00 pc (32.62 ly) | 1 |
| Brightest star | α Hor (3.85m) |
| Nearest star |
GJ 1061 (11.99 ly, 3.66 pc) |
| Messier objects | none |
| Meteor showers | ????? ????? |
| Bordering constellations |
Eridanus Hydrus Reticulum Dorado Caelum |
|
Visible at latitudes between +30° and −90°. Best visible at 21:00 (9 p.m.) during the month of December. |
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Horologium is a faint constellation in the southern sky. It was devised by French astronomer Nicolas Louis de Lacaille in 1752, and it remains one of the 88 modern constellations. The constellation's brightest star is Alpha Horologii, an orange giant. R Horologii is a red giant Mira variable with one of the widest ranges in brightness known. Three star systems have exoplanets, while Nu Horologii has a debris disk.
The French astronomer Nicolas Louis de Lacaille first described the constellation in French as l'Horloge à pendule & à secondes (clock with pendulum and seconds hand) in 1752, after he had observed and catalogued almost 10,000 southern stars during a two-year stay at the Cape of Good Hope. He devised fourteen new constellations in uncharted regions of the Southern Celestial Hemisphere not visible from Europe. All but one honoured instruments that symbolised the Age of Enlightenment. Lacaille Latinised the name to Horologium on his 1763 chart.
Covering a total of 248.9 square degrees or 0.603% of the sky, Horologium ranks 58th in area out of the 88 modern constellations. Its position in the Southern Celestial Hemisphere means that the whole constellation is visible to observers south of 23°N. Horologium is bordered by five different constellations: Eridanus (the Po River), Caelum (the chisel), Reticulum (the reticle), Dorado (the dolphinfish/swordfish), and Hydrus (the male water snake). The three-letter abbreviation for the constellation, as adopted by the International Astronomical Union in 1922, is 'Hor'. The official constellation boundaries are defined by a twenty-two sided polygon (illustrated in infobox). In the equatorial coordinate system, the right ascension coordinates of these borders lie between 02h 12.5m and 04h 20.2m, while the declination coordinates are between −39.63° and −67.04°.
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