Pyxis is a faint southern constellation that was one of 14 created by French astronomer Nicolas Louis de Lacaille during his 1751-52 stay in South Africa. It depicts a mariner’s magnetic compass, but this small constellation is rather inconspicuous as its brightest star, a blue giant called Alpha Pyxidis, has a visual magnitude of just 3.68.
Pyxis is the 65th largest constellation in the sky, and is visible to observers located between +50° and -90° of latitude, although best seen from January through to March. The Milky Way passes through Pyxis, with the constellation’s nearest neighbors including Antlia, Hydra, Puppis and Vela. One way to locate Pyxis is by following an imaginary line running through the tail of Canis Major to just the other side of Puppis.
Heavenly Waters Family
Pyxis is a member of the Heavenly Waters family of constellations, together with Carina, Columba, Delphinus, Equuleus, Eridanus, Piscis Austrinus, Puppis and Vela.
Argo Navis is the only constellation recorded by the ancient Greek astronomer Ptolemy (150 AD) that is no longer in use. It represented the ship belonging to Jason and the Argonauts during his epic journey to retrieve the Golden Fleece, and to the ancient Greeks the four main stars now belonging to Pyxis depicted the ship’s mast. Argo Navis has since been divided into three separate constellations with nautical association, namely Carina (keel), Puppis (stern), and Vela (sails).
During his 1751-52 survey of the southern skies, Frenchman Nicolas Louis de Lacaille subsequently used the stars previously around the Argo’s mast to form a new, separate constellation he called Pixis Nautica (“mariner’s compass”). The name was eventually shortened to just Pyxis, and adopted by the International Astronomical Union (IAU) in 1930.
– Alpha Pyxidis, the constellation’s brightest star, is a blue giant (B1.5III) located 880 light years away with a visual magnitude of 3.67, although as a Beta Cephei variable it experiences slight variations in its brightness. It has 10 times our sun’s mass, six times its radius, and is around 10,000 times brighter.
– Beta Pyxidis, the second brightest star in Pyxis, is a yellow supergiant (G7Ib-II) situated around 420 light years from our solar system with a magnitude of 3.954. It has about 28 times our sun’s radius, and forms the southern most point of the constellation.
– Gamma Pyxidis, the constellation’s third brightest star, is an orange giant (K3III) that lies 209 light years from the Sun with a visual magnitude of 4.03. The star marks the northernmost point of the constellation.
Other stars of interest in Pyxis includes the multiple star systems Kappa Pyxidis, Zeta Pyxidis, and Delta Pyxidis; the yellow giant Lambda Pyxidis; and the red giant Theta Pyxidis.
Notable Deep Sky Objects
There are no Messier objects in Pyxis, but it does contains a number of interesting deep-sky objects.
– Pyxis globular cluster is a 1.3 billion year-old cluster around 130,000 light-years from Earth that is thought to contain thousands of individual stars. It is also located around 133,000 light-years from our Milky Way’s center along an orbital plane of the Large Magellanic Cloud, raising suggestions that it may actually be a detached LMC object that was subsequently captured by our Milky Way galaxy.
– NGC 2818 is a planetary nebula that was caused by a dying star ejecting its gaseous outer layers into space, with its beautiful colors representing a range of gaseous emissions, including nitrogen (red), hydrogen (green), and oxygen (blue). The nebula appears to lie within an open star cluster called NGC 2818A, and is 3.25 light years across and around 10,400 light years distant.
– NGC 2627 is an open cluster consisting of around 40 stars that is situated about 8000 light years from Earth. Its stars appear very dim in the night sky, and with a combined magnitude of 8.4 can therefore only be seen using a large telescope.
– NGC 2613 is massive, barred spiral galaxy located around 60 million light years with an apparent visual magnitude of 10.6.