Fact sheet
- Latin name
- Circinus (Cir)
- Brightest star
- α Circini (α Cir)
- Relative brightness
- 3.18 mag
- Hipparcos catalogue
- HIP 71908
- Area
- 93 deg² (rank: 85 out of 88)
- Right ascension
- 13h 38m 43s to 15h 30m 22s
- Declination
- -70° 37' 28'' to -55° 26' 11''
- Neighbouring constellations
- Lupus, Centaurus, Musca, Apus, Triangulum Australe, Norma
Visibility
The constellation Circinus
Circinus is a constellation of the southern hemisphere. It is partly circumpolar around the South Pole. This means that some of its stars are so close to the celestial pole that they never set as seen from Sydney. Part of the constellation is therefore above the horizon all year round there.
It is the fourth smallest constellation in the sky, and it lies between the front hooves of the constellation Centaurus and the constellation Triangulum Australe. Its closeness to the bright stars α Centauri and β Centauri makes the constellation Circinus look even less noticeable. However, these two stars are also a good guide for finding this constellation. Circinus contains the Circinus Galaxy, some 13 million light years away and one of the nearest active galaxies. Because it lies behind the band of the Milky Way, it was not discovered until 1977.
History
The French theologian Nicolas-Louis de Lacaille, who devoted his life to astronomy, geodesy and mathematics, introduced 14 new constellations of the southern hemisphere. In 1750, he set off on a four-year journey to the Cape of Good Hope in order to observe, among other things, the constellations of the southern sky. During this time, he catalogued almost 10,000 stars. Nicolas-Louis de Lacaille named most of his new constellations after technical instruments. In this way, the constellations Sculptor, Fornax, Caelum, Antlia, Pictor, Microscopium, Reticulum, Octans, Horologium, Pyxis, Mensa, Telescopium, Norma and Circinus came into being. He also divided the large ancient constellation Argo Navis into the three constellations Carina, Puppis and Vela. His star catalogue of the southern sky was published in 1763, one year after his death, under the title “Coelum Australe Stelliferum”. What his 14 new constellations have in common is that they consist of relatively faint stars.
Already in the Middle Ages, the pair of compasses was highly valued in the fields of geometry, planning and the cosmic order. It was also an important tool for seafaring in earlier times, because it was used to determine a ship's position on the high seas. The pair of compasses was immortalised in the sky in a slightly opened form.
