From Wikipedia, the free encyclopedia
Jump to: navigation, search
For other uses, see Pyxis (disambiguation).
Abbreviation Pyx
Genitive Pyxidis
Pronunciation /ˈpɪksɨs/, genitive /ˈpɪksɨdɨs/
Symbolism the compass box
Right ascension 9
Declination −30
Family Heavenly Waters
Quadrant SQ2
Area 221 sq. deg. (65th)
Main stars 3
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)
Messier objects None
Meteor showers None
Visible at latitudes between +50° and −90°.
Best visible at 21:00 (9 p.m.) during the month of March.

Pyxis (/ˈpɪksɨs/; 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.[1] The Greeks identified the four main stars of Pyxis as the mast of the great ship.[2]

Pyxis can be seen overlying the mast of Argo Navis in this plate from Urania's Mirror (1825).

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.[3]

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.[4]

In ancient Chinese astronomy, Alpha, Beta and Gamma Pyxidis formed part of Tianmiao a Celestial Temple honouring the ancestors of the Emperor, along with stars from neighbouring Antlia.[4]


Pyxis is a small constellation 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'.[5] 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°.[6]

Notable features[edit]


With a visual magnitude of 3.68, Alpha Pyxidis is the brightest star in the constellation. It is a blue-white star of spectral type B1.5III which lies around 850 light years away.[7] The second brightest star at magnitude 3.97 is Beta Pyxidis, a yellow bright giant or supergiant of spectral type G7Ib-II around 420 light years distant.[8] It has a companion star of magnitude 12.5 separated by 9 arcseconds.[9] Gamma Pyxidis is an orange giant of spectral type K3III which lies around 209 light years distant. Its visual magnitude is 4.03.[10] 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.[3] A multiple star system, Kappa has a visual magnitude of 4.58 and is 560 light years distant. The primary component is an orange giant of spectral type K4/K5III.[11] 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. It is 522 light years distant.[12]

Located around 4 degrees northeast of Alpha is T Pyxidis,[13] 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,[14] have a mass of 1.2 solar masses and size of 1.65 that of our sun, and revolve around each other every 3.2 days.[15] The system is classified as a RS Canum Venaticorum variable and lies around 184 light years away.[14] 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 our sun. One is around five times as luminous as the sun and the other around four times as luminous.[16] The system is classified as a Beta Lyrae variable, with an average visual magnitude of 9.1 and lies around 1220 light years away.[17] 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.[12] 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.[18]

The closest star to earth in the constellation is Gliese 318, a white dwarf of spectral class DA5 and visual magnitude 12.00,[19] which lies 26 light years away.[20] 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.[21]

Deep sky objects[edit]

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 which lies within a dim open cluster of magnitude 8.2.[22] NGC 2613 is a spiral galaxy of magnitude 10.5 which appears spindle shaped as it is almost edge-on to observers on Earth.[23]

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.[24]

In popular culture[edit]


  1. ^ Wagman, Morton (2003). Lost Stars: Lost, Missing and Troublesome Stars from the Catalogues of Johannes Bayer, Nicholas Louis de Lacaille, John Flamsteed, and Sundry Others. Blacksburg, VA: The McDonald & Woodward Publishing Company. p. 262. ISBN 978-0-939923-78-6. 
  2. ^ Carole Stott, et al. (2006) Eyewitness Companions: Astronomy, p. 210 (ISBN 9780756648459).
  3. ^ a b Wagman 2003, p. 261-62.
  4. ^ a b Ridpath, Star Tales Pyxis.
  5. ^ Russell 1922, p. 469.
  6. ^ IAU, The Constellations, Pyxis.
  7. ^ Kaler, Alpha Pyxidis.
  8. ^ SIMBAD Beta Pyxidis.
  9. ^ SIMBAD CD-34 5128B.
  10. ^ SIMBAD Gamma Pyxidis.
  11. ^ SIMBAD Kappa Pyxidis.
  12. ^ a b Tabur & Bedding 2009.
  13. ^ Motz & Nathanson 1988, pp. 383–84.
  14. ^ a b SIMBAD TY Pyxidis.
  15. ^ Andersen & Popper 1975.
  16. ^ Bell & Malcolm 1987.
  17. ^ SIMBAD RZ Pyxidis.
  18. ^ Wils, Patrick (15 November 2011). "VY Pyxidis". AAVSO Website. American Association of Variable Star Observers. Retrieved 13 July 2014. 
  19. ^ SIMBAD GJ 318.
  20. ^ Sion 2009.
  21. ^ Anglada-Escude et al. 2012.
  22. ^ Inglis 2004, p. 39.
  23. ^ O'Meara 2007, p. 82.
  24. ^ Henize 2–10.


Online sources

External links[edit]

Coordinates: Sky map 09h 00m 00s, −30° 00′ 00″