Circinus Constellation: The Ultimate Guide

Circinus is classified as one of the 88 modern constellations. It does not appear or has no associated history in ancient Western cultures because it was not visible in those regions.

It is known that Circinus is one of the most tenues constellations and that most of its stars cannot be seen with the naked eye, so it was necessary to wait for telescopes to be invented to see it.

In 1756 Lacaille introduced the constellation of Circinus with the French name of Le Compas (the Compass) in a chart of the southern celestial hemisphere.

In the celestial chart of Lacaille, you can see the constellations Norma, Circinus, and Triangulum Australe represented with a square, a compass, and a topographic level, respectively, all in a set of instruments used by cartographers.

The constellation received its current Latin name in 1763 when Lacaille published an update of the celestial map with the Latin names of the constellations he had introduced.

In 1922 the International Astronomical Association added the constellation Circinus to the 88 official night sky constellations. Since then, it has not undergone significant modifications in its limits.

Circinus currently covers an area of 93 square degrees. It is, therefore, the fourth-smallest constellation among the 88 modern constellations out there.

Circinus resides in the third quadrant of the Southern Hemisphere (SQ3) between latitudes 30° N and 90° S., Wich means that we can see the constellation in the night sky from all countries of the southern hemisphere of the earth and some countries of the northern hemisphere.

Circinus is visible in America, Europe, Africa, Australia, and Antarctica.

Circinus is not visible in regions above 30°N such as Canada, most of Europe such as Italy, France, or Germany, nor in Russia, Greenland, Japan, and Alaska.

The best month to visualize the constellation Circinus is July, which is visible during the summer in the northern hemisphere. In the southern hemisphere, it is visible during the fall and all winter.

The constellation Circinus is very dim, so you can lean on the Centaurus to locate it since both constellations are very close to each other.

The easiest way to locate the constellation Circinus is to locate the fourth brightest star in the sky, Alpha Centauri, located in the constellation Centaurus. The constellation Circinus is located next to Alpha Centauri.

The constellations bordering Circinus are Centaurus, Musca, Apus, Triangulum Australe, Norma, and Lupus.

In addition, Circinus belongs to the family of constellations discovered by Lacaille; these include Antlia, Caelum, Fornax, Horologium, Mensa, Microscopium, Norma, Octans, Pictor, Reticulum, Sculptor, and Telescopium.

The constellation Circinus officially contains 39 stars, of which 3 form the central figure of the constellation; these are Alpha Circini, Beta Circini, and Gamma Circini.

This is the brightest star in the constellation Circinus, with an apparent magnitude of +3.19. Alpha Circini is 53.5 light-years away from the Solar System.

The main characteristic of Alpha Circini is that it is an Alpha2 Canum Venaticorum variable.

These variables have solid magnetic fields located on the star's surface, where diffusion and elevation processes increase the temperature level of certain elements.

With an apparent magnitude of +4.46, It is the third brightest star in the constellation Circinus. It is about 509 light-years from the Solar System.

Gamma Circini is a blue-white subgiant star of spectral type B5 IV with a luminosity 366 times greater than the Sun and a diameter ten times larger.

Circinus is also home to a couple of deep-sky objects. Deep-sky objects often signify star clusters, nebulae (interstellar cloud bodies), or galaxies.

In the case of Circinus, because it is a small constellation, it only has star clusters and nebulae; some of these are:

It is an open cumulus in the southern constellation of Circinus, with a magnitude of 7.9 being the most notable deep-sky object in the constellation.

This open cluster is approximately 800 million years old and is 3500 light-years apart. It covers a 12-light-year region along the northern border of the constellation.

It is a planetary nebula in the constellation Circinus. With an apparent magnitude of 9.8 around a central star of magnitude 14.2.

This nebula is 5.2 degrees west-southwest of the star Alpha Circini. It features reddish colors that are only perceptible with professional telescopes.

Within the limits of the constellation, Circinus occurs the meteor shower called Alpha Circinids (ACI), which occurs in early June, with June 4 being the day of most significant exposure.

• Circinus is a constellation located primarily in the southern hemisphere. Its name comes from Latin and signifies "The Compass."
• The constellation Circinus was first introduced in 1756 by Nicolas-Louis de Lacaille's French astronomer.
• The constellation Circinus lies between 30° N and 90° S. The best month to observe the constellation is July.
• The easiest way to locate the constellation Circinus is to locate the fourth brightest star in the sky, Alpha Centauri, located in the constellation Centaurus. The constellation Circinus is located right next to Alpha Centauri.
• The brightest star in the constellation Circinus is Alpha Circini (α Cir /HD 128898/HR 5463), with an apparent magnitude of +3.19.
• The most notable deep-sky body of the constellation Circinus is the open star cluster NGC 5823.
• Circinus' most notable shower of stars is the Alpha Circinids (ACI) which occurs on June 4.

1. https://www.constellation-guide.com/constellation-list/circinus-constellation/
2. http://www.seasky.org/constellations/constellation-circinus.html
3. https://www.universetoday.com/20185/circinus-constellation/
4. https://www.universeguide.com/constellation/circinus