Circinus is a small, dim constellation in the southern sky that was initially identified in 1756 by Nicolas-Louis de Lacaille, a French astronomer. Its name comes from the Latin word compass, which refers to the drafting tool used to draw circles (not to be confused with Pyxis, a constellation that represents a north-pointing mariner's compass). Alpha Circini, with an apparent magnitude of 3.19, is the brightest star in the constellation. It is the brightest fast oscillating Ap star in the night sky, and it is slightly changeable. BX Circini is a dim star considered to have arisen from the merger of two white dwarfs, while AX Circini is a Cepheid variable viewable with the naked eye. There are planetary systems around two sun-like stars: HD 134060 has two tiny planets and HD 129445 has a Jupiter-like planet. Chinese observers observed Supernova SN 185 at Circinus in the year 185 AD. More recently, in the twentieth century, two novae were discovered.
The Milky Way travels through the constellation, with noteworthy objects such as NGC 5823, an open cluster, and NGC 5315, a planetary nebula. Circinus is home to the Circinus Galaxy, which was found in 1977 and is the Milky Way's closest Seyfert galaxy. This constellation is also home to the Alpha Circinids (ACI), a meteor shower discovered in 1977. |
History
Nicolas-Louis de Lacaille, a French astronomer, first charted the southern sky in 1756 and named the constellation Circinus le Compas, which represents a pair of dividing compasses. Lacaille depicted the constellations of Norma, Circinus, and Triangulum Australe as a set square and ruler, a compass, and a surveyor's level, respectively, in a set of draughtsman's instruments on that map. When Lacaille issued an updated sky map with Latin names for the constellations he introduced in 1763, Circinus was given its current name. |
Characteristics
Circinus is located near the Alpha and Beta Centauri stars and is bordered by Centaurus, Musca, Apus, Triangulum Australe, Norma, and Lupus. The entire constellation is only visible south of latitude 30° N due to its declination of 50° to 70°. A polygon of fourteen segments defines the official constellation limits, which were established by Belgian astronomer Eugène Delporte in 1930.
These borders' right ascension coordinates are between 13h 38.4m and 15h 30.2m in the equatorial coordinate system, while their declination coordinates are between 55.43° and 70.62°. Every year on July 30th, at 9 p.m., Circinus ends. (James 2011) The International Astronomical Union chose "Cir" as the standard three-letter abbreviation for the constellation in 1922. (Russell 1922)
Circinus is located near the Alpha and Beta Centauri stars and is bordered by Centaurus, Musca, Apus, Triangulum Australe, Norma, and Lupus. The entire constellation is only visible south of latitude 30° N due to its declination of 50° to 70°. A polygon of fourteen segments defines the official constellation limits, which were established by Belgian astronomer Eugène Delporte in 1930.
These borders' right ascension coordinates are between 13h 38.4m and 15h 30.2m in the equatorial coordinate system, while their declination coordinates are between 55.43° and 70.62°. Every year on July 30th, at 9 p.m., Circinus ends. (James 2011) The International Astronomical Union chose "Cir" as the standard three-letter abbreviation for the constellation in 1922. (Russell 1922)
Deep-sky Objects
NGC 5823 – Open Cluster
NGC 5822 – Open Cluster
NGC 5715 – Faint Open Cluster
NGC 5315 – Planetary Nebula
Bermes 145 – Dark Reflection Nebula
ESO 97-G13 – Circinus Galaxy – Spiral Galaxy
Main stars - 3
Bayer stars - 9
Stars with planets - 2
Stars brighter than magnitude 3.00 - 0
Stars within 32 ly - 0
Bordering
constellations
meteor shower - Alpha Circinids (ACI) – Mid May to mid-June - Peak early June
NGC 5823 – Open Cluster
NGC 5822 – Open Cluster
NGC 5715 – Faint Open Cluster
NGC 5315 – Planetary Nebula
Bermes 145 – Dark Reflection Nebula
ESO 97-G13 – Circinus Galaxy – Spiral Galaxy
Main stars - 3
Bayer stars - 9
Stars with planets - 2
Stars brighter than magnitude 3.00 - 0
Stars within 32 ly - 0
Bordering
constellations
- Centaurus
- Musca
- Apus
- Triangulum Australe
- Norma
- Lupus
meteor shower - Alpha Circinids (ACI) – Mid May to mid-June - Peak early June