|Pronunciation||//, genitive //|
|Symbolism||the compass box|
|Area||221 sq. deg. (65th)|
|Stars with planets||4|
|Stars brighter than 3.00m||0|
|Stars within 10.00 pc (32.62 ly)||1|
|Brightest star||α Pyx (3.68m)|
|Nearest star||Gliese 318
(30.13 ly, 9.24 pc)
|Visible at latitudes between +50° and −90°.
Best visible at 21:00 (9 p.m.) during the month of March.
Pyxis (//; Greek: box) is a small and faint constellation in the southern sky. Its name is Latin for a mariner's compass (it should not be confused with Circinus, which represents a draftsman's compasses). Pyxis is completely visible from latitudes south of 53 degrees north, with its best evening-sky visibility in January through March. The brightest star is Alpha Pyxidis at magnitude 3.68.
Pyxis was introduced by Nicolas Louis de Lacaille in the 18th century; he called it Pyxis Nautica, but the name was shortened. The constellation is located close to those forming the old constellation of Argo Navis (the ship Argo), and in the 19th century astronomer John Herschel suggested renaming Pyxis to 'Malus, the mast', but the suggestion was not followed.
The French astronomer Nicolas Louis de Lacaille first described the constellation as la Boussole (the Marine Compass) and gave Bayer designations to ten stars now named Alpha to Lambda Pyxidis (he skipped the Greek letter iota). He renamed it Pixis [sic] Nautica on his 1763 chart. The Greeks identified the four main stars of Pyxis as the mast of the great ship.
John Herschel (in 1844) attempted to resurrect the classical configuration by renaming it Malus (the "Mast"), a suggestion followed by Francis Baily, but Benjamin Gould restored La Caille's nomenclature.
Johann Bode (1747–1826) created the constellation Lochium Funis (the "Log and Line," a nautical device once used for measuring speed and distance traveled at sea) around Pyxis but this did not survive.
Covering 220.8 square degrees and hence 0.535% of the sky, Pyxis ranks 65th of the 88 modern constellations by area. Its position in the Southern Celestial Hemisphere means that the whole constellation is visible to observers north of 52°N.[a] A small constellation, it is bordered by Hydra to the north, Puppis to the west, Vela to the south, and Antlia to the east. The three-letter abbreviation for the constellation, as adopted by the International Astronomical Union in 1922, is 'Pyx'. The official constellation boundaries, as set by Eugène Delporte in 1930, are defined by a polygon of eight segments (illustrated in infobox). In the equatorial coordinate system, the right ascension coordinates of these borders lie between 10h 32.8m and 27h 42.5m, while the declination coordinates are between −17.41° and −37.29°.
With a visual magnitude of 3.68, Alpha Pyxidis is the brightest star in the constellation. Located 880 ± 30 light-years distant from Earth, it is a blue-white star of spectral type B1.5III that is around 22,000 times as luminous as the Sun and has 9.4 ± 0.7 times its diameter. It began life with a mass 12.1 ± 0.6 times that of the Sun, almost 15 million years ago. Its light is dimmed by 30% due to interstellar dust, so would be a brighter magnitude of 3.31 if not for this. The second brightest star at magnitude 3.97 is Beta Pyxidis, a yellow bright giant or supergiant of spectral type G7Ib-II that is around 435 times as luminous as the Sun, lying 420 ± 10 light-years distant away from Earth. It has a companion star of magnitude 12.5 separated by 9 arcseconds. Gamma Pyxidis is a star of magnitude 4.02 that lies 207 ± 2 light-years distant. It is an orange giant of spectral type K3III that has exhausted its core hydrogen and cooled and swollen to 3.7 times the diameter of the Sun.
Kappa Pyxidis was catalogued but not given a Bayer designation (Greek letter) by Lacaille, however Gould felt the star was bright enough to warrant a letter. Kappa has a visual magnitude of 4.62 and is 560 ± 50 light years distant. An orange giant of spectral type K4/K5III, it is separated by 2.1 arcseconds from a magnitude 10 star. Theta Pyxidis is a red giant of spectral type M1III and semi-regular variable with two measured periods of 13 and 98.3 days, and an average visual magnitude of 4.71, and is 500 ± 30 light-years distant from Earth. It has swollen to 5.4 times the diameter of the Sun.
Located around 4 degrees northeast of Alpha is T Pyxidis, a binary star system located around 3,300 light-years away from Earth. A recurrent nova, it has brightened to the 7th magnitude in the years 1890, 1902, 1920, 1944, 1966 and 2011 from a baseline of around 14th magnitude.
TY Pyxidis is an eclipsing binary star of combined visual magnitude 6.9. The two components are both of spectral type G5IV, have a mass of 1.2 solar masses and size of 1.65 that of the Sun, and revolve around each other every 3.2 days. The system is classified as a RS Canum Venaticorum variable and lies around 184 light years away. RZ Pyxidis is another eclipsing binary system, made up of two young stars less than 200,000 years old. Both are hot blue-white stars of spectral type B7V and are around 2.5 times the size of the Sun. One is around five times as luminous as the sun and the other around four times as luminous. The system is classified as a Beta Lyrae variable, with an average visual magnitude of 9.1 and lies around 1220 light-years away. AK Pyxidis is a red giant of spectral type M5III and semi-regular variable with an average visual magnitude of 6.42. It lies 771 light-years away. VY Pyxidis is a BL Herculis variable (type II Cepheid), ranging between apparent magnitudes 7.13 and 7.40 over a period of 1.23995 days.
The closest star to earth in the constellation is Gliese 318, a white dwarf of spectral class DA5 and visual magnitude 12.00, which lies 26 light years away. WISEPC J083641.12-185947.2 is a brown dwarf located around 72 light years from earth which was discovered by infrared astronomy in 2011.
Pyxis is home to three stars with confirmed planetary systems: HD 73256 is a yellow star of spectral type G9V with a hot Jupiter, HD 73256 b, orbiting it every 2.55 days. It is 119 light years away. HD 73267 is a star with its companion HD 73267 b orbiting every 1260 days. Gliese 317 is a red dwarf around 50 light years distant which is orbited by two gas giant planets, and is a good candidate for future searches for more terrestrial rocky planets.
Deep sky objects
Pyxis lies in the plane of the Milky Way, although part of the eastern edge is dark, with material obscuring our galaxy arm there. NGC 2818 is a planetary nebula that lies within a dim open cluster of magnitude 8.2. NGC 2613 is a spiral galaxy of magnitude 10.5 which appears spindle shaped as it is almost edge-on to observers on Earth.
Henize 2-10 is a dwarf galaxy which lies some 30 million light years away. It is notable for having a black hole around a million solar masses at its centre. Known as a starburst galaxy due to very high rates of star formation, it has a bluish colour due to the huge numbers of young stars within it.
- While parts of the constellation technically rise above the horizon to observers between the 52°N and 72°N, stars within a few degrees of the horizon are to all intents and purposes unobservable.
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- Motz, Lloyd; Nathanson, Carol (1988). The Constellations. New York, New York: Doubleday. pp. 383–84. ISBN 978-0-385-17600-2.
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- Inglis, Mike (2004). Astronomy of the Milky Way: Observer's Guide to the Southern Sky. New York, New York: Springer. ISBN 1852337427.
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