Horologium (constellation)

Horologium

Constellation
List of stars in Horologium
Abbreviation	Hor
Genitive	Horologii
Pronunciation	/ˌhɒrəˈloʊdʒiəm, -ˈlɒ-/,[1] genitive /ˌhɒrəˈloʊdʒiˌaɪ, -ˈlɒ-/
Symbolism	The Pendulum Clock
Right ascension	02h 12m 48.5665s–04h 20m 18.3390s[2]
Declination	−39.6368256°–−67.0358200°[2]
Quadrant	SQ1
Area	249 sq. deg. (58th)
Main stars	6
Bayer/Flamsteed stars	10
Stars with planets	4
Stars brighter than 3.00m	0
Stars within 10.00 pc (32.62 ly)	1
Brightest star	α Hor (3.85m)
Messier objects	0
Meteor showers	0
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.

Horologium (Latin hōrologium, the pendulum clock, from Greek ὡρολόγιον, lit. 'an instrument for telling the hour') is a constellation of six stars faintly visible in the southern celestial hemisphere. It was first described by the French astronomer Nicolas-Louis de Lacaille in 1756 and visualized by him as a clock with a pendulum and a second hand. In 1922 the constellation was redefined by the International Astronomical Union (IAU) as a region of the celestial sphere containing Lacaille's stars, and has since been an IAU designated constellation. Horologium's associated region is wholly visible to observers south of 23°N.

The constellation's brightest star—and the only one brighter than an apparent magnitude of 4—is Alpha Horologii (at 3.85), an aging orange giant star that has swollen to around 11 times the diameter of the Sun. The long-period variable-brightness star, R Horologii (4.7 to 14.3), has one of the largest variations in brightness among all stars in the night sky visible to the unaided eye. Four star systems in the constellation are known to have exoplanets; at least one—Gliese 1061—contains an exoplanet in its habitable zone.