View source for Astronomy:Pyxis

{{Short description|Constellation in the southern celestial hemisphere}}

{{Infobox constellation
| name = Pyxis
| abbreviation = Pyx
| genitive = Pyxidis
| pronounce = {{IPAc-en|ˈ|p|ɪ|k|s|ᵻ|s}}, genitive {{IPAc-en|ˈ|p|ɪ|k|s|ᵻ|d|ᵻ|s}}
| symbolism = The [[Physics:Compass|compass]] box
| RA = {{RA|9}}
| dec= {{DEC|−30}}
| family = Heavenly Waters
| quadrant = SQ2
| areatotal = 221
| arearank = 65th
| numbermainstars = 3
| numberbfstars = 10
| numberstarsplanets = 3
| numberbrightstars = 0
| numbernearbystars = 1
| brighteststarname = [[Astronomy:Alpha Pyxidis|α Pyx]]
| starmagnitude = 3.68
| neareststarname = [[Astronomy:Gliese 318|Gliese 318]]
| stardistancely = 30.13
| stardistancepc = 9.55
| numbermessierobjects = 0
| bordering = [[Astronomy:Hydra (constellation)|Hydra]]<br />[[Astronomy:Puppis|Puppis]]<br />[[Astronomy:Vela (constellation)|Vela]]<br />[[Astronomy:Antlia|Antlia]]
| latmax = 50
| latmin = [[Earth:South Pole|90]]
| month = March
}}
'''Pyxis'''{{efn|1=Pronounced {{IPAc-en|ˈ|p|ɪ|k|s|ᵻ|s}}; [[Social:Greek language|Greek]] and [[Social:Latin|Latin]] for [[Engineering:Box|box]].<ref>{{L&S|pyxis|ref}}</ref><ref>{{LSJ|puci/s|πυξίς|ref}}.</ref>}} is a small and faint [[Astronomy:Constellation|constellation]] in the southern sky. Abbreviated from '''Pyxis Nautica''', its name is [[Social:Latin|Latin]] for a mariner's compass (contrasting with [[Astronomy:Circinus|Circinus]], which represents a draftsman's compasses). Pyxis was introduced by Nicolas-Louis de Lacaille in the 18th century, and is counted among the [[Astronomy:88 modern constellations|88 modern constellations]].

The [[Astronomy:Galactic plane|plane]] of the [[Astronomy:Milky Way|Milky Way]] passes through Pyxis. A faint constellation, its three brightest stars—[[Astronomy:Alpha Pyxidis|Alpha]], [[Astronomy:Beta Pyxidis|Beta]] and [[Astronomy:Gamma Pyxidis|Gamma Pyxidis]]—are in a rough line. At magnitude 3.68, Alpha is the constellation's brightest star. It is a blue-white star approximately {{convert|880|ly|pc|abbr=off|lk=on}} distant and around 22,000 times as [[Astronomy:Luminosity|luminous]] as the Sun.

<!-- Editors: PLEASE NOTE that Pyxis is _not_ one of the parts into which Lacaille split Argo. Many people get this wrong!-->Pyxis is located close to the stars that formed the old constellation [[Astronomy:Argo Navis|Argo Navis]], the ship of Jason and the Argonauts. Parts of Argo Navis were the Carina (the keel or hull), the Puppis (the stern), and the Vela (the sails). These eventually became their own constellations. In the 19th century, [[Biography:John Herschel|John Herschel]] suggested renaming Pyxis to Malus (meaning the [[Engineering:Mast (sailing)|mast]]) but the suggestion was not followed.

[[Astronomy:T Pyxidis|T Pyxidis]], located about 4 degrees northeast of Alpha Pyxidis, is a [[Astronomy:Recurrent nova|recurrent nova]] that has flared up to [[Astronomy:Apparent magnitude|magnitude]] 7 every few decades. Also, three star systems in Pyxis have confirmed [[Astronomy:Exoplanet|exoplanet]]s. The [[Astronomy:Pyxis globular cluster|Pyxis globular cluster]] is situated about 130,000 light-years away in the [[Astronomy:Galactic halo|galactic halo]]. This region was not thought to contain [[Astronomy:Globular cluster|globular cluster]]s. The possibility has been raised that this object might have escaped from the [[Astronomy:Large Magellanic Cloud|Large Magellanic Cloud]].<ref name="Irwin 1995"/>

==History==
[[File:Hydra IAU.svg|left|thumb|300px|Pyxis is positioned just south of the star [[Astronomy:Alphard|Alphard]] in the constellation Hydra midway between Virgo and Cancer. Although it is completely visible from latitudes south of 53 degrees north, its best evening-sky visibility is during February and March in the southern hemisphere.]]
In ancient [[Astronomy:Chinese astronomy|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 [[Astronomy:Antlia|Antlia]].<ref name=startales>{{cite web |last=Ridpath |first=Ian |publisher=Self-published |date=1988 |title=Pyxis |work=Star Tales |url=http://www.ianridpath.com/startales/pyxis.html#chinese |access-date=8 October 2012}}</ref>

The French astronomer Nicolas-Louis de Lacaille first described the [[Astronomy:Constellation|constellation]] in French as ''la Boussole'' (the Marine Compass) in 1752,<ref name=ridpathlac>{{cite web |url=http://www.ianridpath.com/startales/lacaille.html |title=Lacaille's Southern Planisphere of 1756 |work=Star Tales |author=Ridpath, Ian |publisher=Self-published |access-date=1 August 2015|author-link=Ian Ridpath }}</ref><ref>{{cite journal |author=Lacaille, Nicolas Louis |year=1756 |title=Relation abrégée du Voyage fait par ordre du Roi au cap de Bonne-espérance |journal=Mémoires de l'Académie Royale des Sciences |pages=519–92 [589] |url=http://gallica.bnf.fr/ark:/12148/bpt6k35505/f787 |language=fr}}</ref> after he had observed and catalogued almost 10,000 southern stars during a two-year stay at the Cape of Good Hope. He devised fourteen new constellations in uncharted regions of the Southern Celestial Hemisphere not visible from Europe. All but one honoured instruments that symbolised the [[Philosophy:Age of Enlightenment|Age of Enlightenment]].{{efn|1=The exception is [[Astronomy:Mensa (constellation)|Mensa]], named for the Table Mountain. The other thirteen (alongside Pyxis) are [[Astronomy:Antlia|Antlia]], [[Astronomy:Caelum|Caelum]], [[Astronomy:Circinus|Circinus]], [[Astronomy:Fornax|Fornax]], [[Astronomy:Horologium (constellation)|Horologium]], [[Astronomy:Microscopium|Microscopium]], [[Astronomy:Norma (constellation)|Norma]], [[Astronomy:Octans|Octans]], [[Astronomy:Pictor|Pictor]], [[Astronomy:Reticulum|Reticulum]], [[Astronomy:Sculptor (constellation)|Sculptor]], and [[Astronomy:Telescopium|Telescopium]].<ref name=wagman/>}} Lacaille Latinised the name to ''Pixis'' [sic] ''Nautica'' on his 1763 chart.<ref name=wagman>{{cite book |last=Wagman |first=Morton |date=2003 |title=Lost Stars: Lost, Missing and Troublesome Stars from the Catalogues of Johannes Bayer, Nicholas Louis de Lacaille, John Flamsteed, and Sundry Others |publisher=The McDonald & Woodward Publishing Company |location=Blacksburg, Virginia |isbn=978-0-939923-78-6 |pages=6–7, 261–62}}</ref><!-- Cites previous three sentences --> The Ancient Greeks identified the four main stars of Pyxis as the mast of the mythological Jason's ship, ''[[Astronomy:Argo Navis|Argo Navis]]''.<ref>{{cite book |author=Ridpath, Ian |year=2006 |title=Eyewitness Companions: Astronomy |page=210 |publisher=DK Publishing (Dorling Kindersley) |location=London, England |isbn=978-0-7566-4845-9}}</ref>

German astronomer Johann Bode defined the constellation Lochium Funis, the Log and Line—a nautical device once used for measuring speed and distance travelled at sea—around Pyxis in his 1801 star atlas, but the depiction did not survive.<ref name=startales2>{{cite web |last=Ridpath |first=Ian |publisher=Self-published |date=1988 |title=Lochium Funis |work=Star Tales |url=http://www.ianridpath.com/startales/lochiumfunis.html |access-date=6 July 2015}}</ref> In 1844 [[Biography:John Herschel|John Herschel]] attempted to resurrect the classical configuration of Argo Navis by renaming it Malus the Mast, a suggestion followed by Francis Baily, but Benjamin Gould restored Lacaille's nomenclature.<ref name=wagman/><!-- cites previous three sentences-->

==Characteristics==
[[File:Constellation Pyxis.jpg|thumb|left|The constellation of Pyxis, the compass, as it can be seen by the naked eye]]
Covering 220.8 square degrees and hence 0.535% of the sky, Pyxis ranks 65th of the [[Astronomy:88 modern constellations|88 modern constellations]] by area.<ref name=tirionconst/> Its position in the Southern Celestial Hemisphere means that the whole constellation is visible to observers south of 52°N.<ref name=tirionconst>{{cite web |url=http://www.ianridpath.com/constellations2.html |title=Constellations: Lacerta–Vulpecula |work=Star Tales |author=Ridpath, Ian |publisher=self-published |access-date=25 June 2015|author-link=Ian Ridpath }}</ref>{{efn|1=While parts of the constellation technically rise above the horizon to observers between the latitudes of 52°N and 72°N, stars within a few degrees of the horizon are to all intents and purposes unobservable.<ref name=tirionconst/>}} It is most visible in the evening sky in February and March.<ref name="saski_boddy2003">{{cite book |last1=Sasaki |first1=Chris |last2=Boddy |first2=Joe |year=2003 |title=Constellations: the stars and stories |publisher=Sterling Publishing Company, Inc |isbn=978-1-4027-0800-8 |page=96 |url=https://books.google.com/books?id=5m_A_AsQVPUC&pg=PA96}}</ref> A small constellation, it is bordered by [[Astronomy:Hydra (constellation)|Hydra]] to the north, [[Astronomy:Puppis|Puppis]] to the west, [[Astronomy:Vela (constellation)|Vela]] to the south, and Antlia to the east. The three-letter abbreviation for the constellation, as adopted by the [[Organization:International Astronomical Union|International Astronomical Union]] in 1922, is "Pyx".<ref name="pa30_469">{{cite journal |last=Russell |first=Henry Norris |author-link=Henry Norris Russell |title=The New International Symbols for the Constellations |journal=Popular Astronomy |volume=30 |page=469 |bibcode=1922PA.....30..469R |year=1922}}</ref> The official constellation boundaries, as set by Belgian astronomer [[Biography:Eugène Joseph Delporte|Eugène Delporte]] in 1930, are defined by a [[Polygon|polygon]] of eight sides (''illustrated in infobox''). In the [[Astronomy:Equatorial coordinate system|equatorial coordinate system]], the [[Right ascension|right ascension]] coordinates of these borders lie between {{RA|8|27.7}} and {{RA|9|27.6}}, while the [[Declination|declination]] coordinates are between −17.41° and −37.29°.<ref name="boundary">{{Cite journal |title=Pyxis, Constellation Boundary |journal=The Constellations |publisher=International Astronomical Union |url=https://www.iau.org/public/themes/constellations/#pyx |access-date=25 June 2015}}</ref>

==Features==

===Stars===
[[File:Sidney Hall - Urania's Mirror - Noctua, Corvus, Crater, Sextans Uraniæ, Hydra, Felis, Lupus, Centaurus, Antlia Pneumatica, Argo Navis, and Pyxis Nautica.jpg|thumb|right|300px|Pyxis can be seen overlying the mast of Argo Navis|alt=A 19th century coloured engraving of a group of constellations in the Southern Celestial Hemisphere in this plate from ''Urania's Mirror'' (1824).]]
Lacaille gave [[Astronomy:Bayer designation|Bayer designation]]s to ten stars now named Alpha to Lambda Pyxidis, skipping the Greek letters iota and kappa. Although a nautical element, the constellation was not an integral part of the old Argo Navis and hence did not share in the original Bayer designations of that constellation, which were split between Carina, Vela and Puppis.<ref name="wagman" /> Pyxis is a faint constellation, its three brightest stars—[[Astronomy:Alpha Pyxidis|Alpha]], [[Astronomy:Beta Pyxidis|Beta]] and [[Astronomy:Gamma Pyxidis|Gamma Pyxidis]]—forming a rough line.<ref name="cambridge">{{cite book |author1=Moore, Patrick |author2=Tirion, Wil |title=Cambridge Guide to Stars and Planets |publisher=Cambridge University Press |location=Cambridge, United Kingdom |date=1997 |page=[https://archive.org/details/cambridgeguideto00moor/page/118 118] |isbn=978-0-521-58582-8 |url=https://archive.org/details/cambridgeguideto00moor|url-access=registration }}</ref> Overall, there are 41 stars within the constellation's borders with [[Astronomy:Apparent magnitude|apparent magnitude]]s brighter than or equal to 6.5.{{efn|1=Objects of magnitude 6.5 are among the faintest visible to the unaided eye in suburban-rural transition night skies.<ref>{{cite web |url=http://www.skyandtelescope.com/resources/darksky/3304011.html?page=1&c=y |title=The Bortle Dark-Sky Scale |last=Bortle |first=John E. |date=February 2001 |work=Sky & Telescope |publisher=Sky Publishing Corporation |access-date=1 August 2015}}</ref>}}<ref name="tirionconst" />

With an apparent magnitude of 3.68, Alpha Pyxidis is the brightest star in the constellation.<ref name="kaleralpha">{{cite web |last=Kaler |first=Jim |title=Alpha Pyxidis |work=Stars |publisher=University of Illinois |url=http://stars.astro.illinois.edu/sow/alphapyx.html |access-date=6 October 2012}}</ref> Located 880 ± 30 [[Astronomy:Light-year|light-year]]s distant from Earth,<ref name="van Leeuwen2007">{{cite journal |title=Validation of the new Hipparcos reduction |url=http://www.aanda.org/index.php?option=com_article&access=bibcode&Itemid=129&bibcode=2007A%2526A...474..653VFUL |last1=van Leeuwen |first1=F. |journal=Astronomy and Astrophysics |volume=474 |issue=2 |pages=653–64 |year=2007 |arxiv=0708.1752 |bibcode=2007A&A...474..653V |doi=10.1051/0004-6361:20078357|s2cid = 18759600}}</ref> it is a blue-white [[Astronomy:Giant star|giant star]] of spectral type B1.5III that is around 22,000 times as [[Astronomy:Luminosity|luminous]] as the [[Astronomy:Sun|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.<ref name="Nieva 2014">{{cite journal |author1=Nieva, María-Fernanda |author2=Przybilla, Norbert |date=2014 |title=Fundamental properties of nearby single early B-type stars |journal=Astronomy & Astrophysics |volume=566 |pages=11 |doi=10.1051/0004-6361/201423373 |bibcode=2014A&A...566A...7N|arxiv = 1412.1418 |s2cid=119227033 }}</ref><!-- cites previous 2 sentences --> Its light is dimmed by 30% due to [[Astronomy:Cosmic dust|interstellar dust]], so would have a brighter magnitude of 3.31 if not for this.<ref name=kaleralpha/> The second brightest star at magnitude 3.97 is Beta Pyxidis, a yellow [[Astronomy:Bright giant|bright giant]] or [[Astronomy:Supergiant|supergiant]] of spectral type G7Ib-II that is around 435 times as luminous as the Sun,<ref name="Mcdonald">{{cite journal |author=McDonald, I. |author2=Zijlstra, A. A. |author3=Boyer, M. L. |date=2012 |title=Fundamental Parameters and Infrared Excesses of Hipparcos Stars |journal=Monthly Notices of the Royal Astronomical Society |volume=427 |issue=1 |pages=343–57 |bibcode=2012MNRAS.427..343M |arxiv=1208.2037 |doi=10.1111/j.1365-2966.2012.21873.x|s2cid=118665352 }}</ref> lying 420 ± 10 light-years distant away from Earth.<ref name="van Leeuwen2007"/> It has a companion star of magnitude 12.5 separated by 9 arcseconds.<ref>{{cite web |url=http://simbad.u-strasbg.fr/simbad/sim-id?Ident=Bet+Pyx&NbIdent=1&Radius=2&Radius.unit=arcmin&submit=submit+id |title=Beta Pyxidis |work=SIMBAD Astronomical Database |publisher=Centre de Données astronomiques de Strasbourg |access-date=31 July 2015}}</ref> Gamma Pyxidis is a star of magnitude 4.02 that lies 207 ± 2 light-years distant.<ref name="van Leeuwen2007"/> It is an orange giant of spectral type K3III that has cooled and swollen to 3.7 times the diameter of the Sun after exhausting its core hydrogen.<ref name="CADARS">{{cite journal |author1=Pasinetti Fracassini, L. E. |author2=Pastori, L. |author3=Covino, S. |author4=Pozzi, A. |date=2001 |title=Catalogue of Apparent Diameters and Absolute Radii of Stars (CADARS) – Third edition – Comments and statistics |journal=Astronomy & Astrophysics |volume=367 |issue=2 |pages=521–24 |bibcode=2001A&A...367..521P |doi=10.1051/0004-6361:20000451|arxiv = astro-ph/0012289 |s2cid=425754 }}</ref>

[[Astronomy:Kappa Pyxidis|Kappa Pyxidis]] was catalogued but not given a Bayer designation by Lacaille, but Gould felt the star was bright enough to warrant a letter.<ref name="wagman" /> Kappa has a magnitude of 4.62 and is 560 ± 50 light-years distant.<ref name="van Leeuwen2007"/> An orange giant of spectral type K4/K5III,<ref>{{cite web |url=http://simbad.u-strasbg.fr/simbad/sim-id?Ident=Kap+Pyx&NbIdent=1&Radius=2&Radius.unit=arcmin&submit=submit+id |title=Kappa Pyxidis |work=SIMBAD Astronomical Database |publisher=Centre de Données astronomiques de Strasbourg |access-date=1 July 2015}}</ref> Kappa has a luminosity approximately 965 times that of the Sun.<ref name="Mcdonald" /> It is separated by 2.1 arcseconds from a magnitude 10 star.<ref>{{cite book |last1=Privett |first1=Grant |last2=Jones |first2=Kevin |title=The Constellation Observing Atlas |publisher=Springer Science & Business Media |location=New York, New York |date=2013 |page=168 |isbn=978-1-4614-7648-1 |url=https://books.google.com/books?id=uN69BAAAQBAJ&pg=PA168}}</ref> [[Astronomy:Theta Pyxidis|Theta Pyxidis]] is a [[Astronomy:Red giant|red giant]] of spectral type M1III and semi-regular variable with two measured periods of 13 and 98.3 days, and an average magnitude of 4.71,<ref name="tabur">{{cite journal |title=Long-term photometry and periods for 261 nearby pulsating M giants |last1=Tabur |first1=V. |last2=Bedding |first2=T.R. |date=2009 |journal=Monthly Notices of the Royal Astronomical Society |volume=400 |issue=4 |pages=1945–61 |doi=10.1111/j.1365-2966.2009.15588.x |arxiv=0908.3228 |bibcode=2009MNRAS.400.1945T|s2cid=15358380 }}</ref> and is 500 ± 30 light-years distant from Earth.<ref name="van Leeuwen2007"/> It has expanded to approximately 54 times the diameter of the Sun.<ref name="CADARS" />

[[File:Tpyx hst big.jpg|thumb|left|[[Astronomy:Hubble Space Telescope|Hubble Space Telescope]] picture of T Pyxidis, showing ejected material from past eruptions|alt=An image of a central white object surrounded by white and pale blue markers signifying material in a shell-like pattern around it]]
Located around 4 degrees northeast of Alpha is [[Astronomy:T Pyxidis|T Pyxidis]],<ref>{{cite book |last1=Motz |first1=Lloyd |last2=Nathanson |first2=Carol |date=1988 |title=The Constellations |publisher=Doubleday |location=New York, New York |isbn=978-0-385-17600-2 |pages=[https://archive.org/details/constellations00motz/page/383 383–84] |url=https://archive.org/details/constellations00motz/page/383 }}</ref> a binary star system composed of a [[Astronomy:White dwarf|white dwarf]] with around 0.8 times the Sun's mass and a [[Astronomy:Red dwarf|red dwarf]] that orbit each other every 1.8 hours. This system is located around 15,500 light-years away from Earth.<ref name="Chesneau 2011">{{cite journal |author1=Chesneau, O. |author2=Meilland, A. |author3=Banerjee, D. P. K. |author4=Le Bouquin, J.-B. |author5=McAlister, H. |author6=Millour, F. |author7=Ridgway, S. T. |author8=Spang, A. |author9=ten Brummelaar, T. |author10=Wittkowski, M. |author11=Ashok, N. M. |author12=Benisty, M. |author13=Berger, J.-P. |author14=Boyajian, T. |author15=Farrington, Ch. |author16=Goldfinger, P. J. |author17=Merand, A. |author18=Nardetto, N. |author19=Petrov, R. |author20=Rivinius, Th. |author21=Schaefer, G. |author22=Touhami, Y. |author23=Zins, G. |date=2011 |title=The 2011 outburst of the recurrent nova T Pyxidis. Evidence for a face-on bipolar ejection |journal=Astronomy & Astrophysics |volume=534 |id=L11 |page=5 |doi=10.1051/0004-6361/201117792 |bibcode=2011A&A...534L..11C|arxiv = 1109.4534 |s2cid=10318633 }}</ref> A [[Astronomy:Nova#Recurrent novae|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. These outbursts are thought to be due to the white dwarf accreting material from its companion and ejecting periodically.<ref name="AAVSOT">{{cite web |url=http://www.aavso.org/vsots_tpyx |title=T Pyxidis: Enjoy the Silence |author=Davis, Kate |date=19 April 2011 |work=Variable Star of the Month |publisher=American Association of Variable Star Observers |access-date=31 July 2015}}</ref>

[[Astronomy:TY Pyxidis|TY Pyxidis]] is an [[Astronomy:Binary star#Eclipsing binaries|eclipsing binary star]] whose apparent magnitude ranges from 6.85 to 7.5 over 3.2 days.<ref name="AAVSOTY">{{cite web |url=http://www.aavso.org/vsx/index.php?view=detail.top&oid=27245 |title=AK Pyxidis |author=Watson, Christopher |date=4 January 2010 |work=The International Variable Star Index |publisher=American Association of Variable Star Observers |access-date=30 July 2015}}</ref> The two components are both of spectral type G5IV with a diameter 2.2 times,<ref name="Strassmeier">{{cite journal |title=Starspots |author=Strassmeier, Klaus G. |date=2009 |journal=The Astronomy and Astrophysics Review |volume=17 |issue=3 |pages=251–308 |doi=10.1007/s00159-009-0020-6
|bibcode=2009A&ARv..17..251S|doi-access=free }}</ref> and mass 1.2 times that of the Sun, and revolve around each other every 3.2 days.<ref>{{cite journal |title=The G-type eclipsing binary TY Pyxidis. |last1=Andersen |first1=J. |last2=Popper |first2=D. M. |date=1975 |journal=Astronomy and Astrophysics |volume=39 |pages=131–34 |bibcode=1975A&A....39..131A }}</ref> The system is classified as a [[Astronomy:RS Canum Venaticorum variable|RS Canum Venaticorum variable]], a binary system with prominent [[Astronomy:Starspot|starspot]] activity,<ref name="AAVSOTY" /> and lies 184 ± 5 light-years away.<ref name="van Leeuwen2007"/> The system emits X-rays, and analysing the emission curve over time led researchers to conclude that there was a loop of material arcing between the two stars.<ref name="Pres 1995">{{cite journal |author1=Pres, Pawel |author2=Siarkowski, Marek |author3=Sylwester, Janusz |date=1995 |title=Soft X-ray imaging of the TY Pyx binary system - II. Modelling the interconnecting loop-like structure |journal=Monthly Notices of the Royal Astronomical Society |volume=275 |issue=1 |pages=43–55 |bibcode=1995MNRAS.275...43P|doi = 10.1093/mnras/275.1.43 |doi-access=free }}</ref> [[Astronomy:RZ Pyxidis|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.<ref>{{cite journal |title=RZ Pyxidis – an early-type marginal contact binary |last1=Bell |first1=S. A. |last2=Malcolm |first2=G. J. |journal=[[Organization:Monthly Notices of the Royal Astronomical Society|Monthly Notices of the Royal Astronomical Society]] |issn=0035-8711 |volume=227 |issue=2 |date=1987 |pages=481–500 |bibcode=1987MNRAS.227..481B |doi=10.1093/mnras/227.2.481|doi-access=free }}</ref> The system is classified as a [[Astronomy:Beta Lyrae variable|Beta Lyrae variable]], the apparent magnitude varying from 8.83 to 9.72 over 0.66 days.<ref name="AAVSORZ">{{cite web |url=http://www.aavso.org/vsx/index.php?view=detail.top&oid=27199 |title=RZ Pyxidis |author=Watson, Christopher |date=4 January 2010 |work=The International Variable Star Index |publisher=American Association of Variable Star Observers |access-date=31 July 2015}}</ref> [[Astronomy:XX Pyxidis|XX Pyxidis]] is one of the more-studied members of a class of stars known as [[Astronomy:Delta Scuti variable|Delta Scuti variable]]s<ref name="Aerts 2002">{{cite journal |author1=Aerts, C. |author2=Handler, G. |author3=Arentoft, T. |author4=Vandenbussche, B. |author5=Medupe, R. |author6=Sterken, C. |date=2002 |title=The δ Scuti star XX Pyx is an ellipsoidal variable |journal=Monthly Notices of the Royal Astronomical Society |volume=333 |issue=2 |pages=L35–L39 |doi=10.1046/j.1365-8711.2002.05627.x |bibcode=2002MNRAS.333L..35A|doi-access=free }}</ref>—short period (six hours at most) pulsating stars that have been used as [[Astronomy:Cosmic distance ladder#Standard candles|standard candles]] and as subjects to study astroseismology.<ref>{{cite web |url=http://www.aavso.org/vsots_delsct |title=Delta Scuti and the Delta Scuti Variables |last=Templeton |first=Matthew |date=16 July 2010 |work=Variable Star of the Season |publisher=AAVSO (American Association of Variable Star Observers) |access-date=5 September 2015}}</ref> Astronomers made more sense of its pulsations when it became clear that it is also a binary star system. The main star is a white main sequence star of spectral type A4V that is around 1.85 ± 0.05 times as massive as the Sun. Its companion is most likely a red dwarf of spectral type M3V, around 0.3 times as massive as the Sun. The two are very close—possibly only 3 times the diameter of the Sun between them—and orbit each other every 1.15 days. The brighter star is deformed into an egg shape.<ref name="Aerts 2002"/><!-- cites previous 5 sentences -->

[[Astronomy:AK Pyxidis|AK Pyxidis]] is a red giant of spectral type M5III and semi-regular variable that varies between magnitudes 6.09 and 6.51.<ref name="AAVSOAK">{{cite web |url=http://www.aavso.org/vsx/index.php?view=detail.top&oid=27245 |title=AK Pyxidis |author=Watson, Christopher |date=25 August 2009 |work=The International Variable Star Index |publisher=American Association of Variable Star Observers |access-date=29 July 2015}}</ref> Its pulsations take place over multiple periods simultaneously of 55.5, 57.9, 86.7, 162.9 and 232.6 days.<ref name="tabur" /> [[Astronomy:UZ Pyxidis|UZ Pyxidis]] is another semi-regular variable red giant, this time a [[Astronomy:Carbon star|carbon star]], that is around 3560 times as luminous as the Sun with a surface temperature of 3482 K, located 2116 light-years away from Earth.<ref name="Mcdonald" /> It varies between magnitudes 6.99 and 7.83 over 159 days.<ref name="AAVSOUZ">{{cite web |url=http://www.aavso.org/vsx/index.php?view=detail.top&oid=27245 |title=AK Pyxidis |author=Otero, Sebastian Alberto |date=15 April 2012 |work=The International Variable Star Index |publisher=American Association of Variable Star Observers |access-date=31 July 2015}}</ref> [[Astronomy:VY Pyxidis|VY Pyxidis]] is a [[Astronomy:BL Herculis variable|BL Herculis variable]] ([[Astronomy:Type II Cepheid|type II Cepheid]]), ranging between [[Astronomy:Apparent magnitude|apparent magnitude]]s 7.13 and 7.40 over a period of 1.24 days.<ref name="AAVSOVY">{{cite web |url=http://www.aavso.org/vsx/index.php?view=detail.top&oid=27224 |title=VY Pyxidis |author=Wils, Patrick |date=15 November 2011 |work=AAVSO Website |publisher=American Association of Variable Star Observers |access-date=13 July 2014}}</ref> Located around 650 light-years distant, it shines with a [[Astronomy:Luminosity|luminosity]] approximately 45 times that of the Sun.<ref name="Mcdonald" />

The closest star to Earth in the constellation is [[Astronomy:Gliese 318|Gliese 318]], a white dwarf of spectral class DA5 and magnitude 11.85.<ref name="Gaia">{{cite journal |author1=Pancino, E. |author2=Altavilla, G. |author3=Marinoni, S. |author4=Cocozza, G. |author5=Carrasco, J. M. |author6=Bellazzini, M. |author7=Bragaglia, A. |author8=Federici, L. |author9=Rossetti, E. |author10=Cacciari, C. |author11=Balaguer Núñez, L. |author12=Castro, A. |author13=Figueras, F. |author14=Fusi Pecci, F. |author15=Galleti, S. |author16=Gebran, M. |author17=Jordi, C. |author18=Lardo, C. |author19=Masana, E. |author20=Monguió, M. |author21=Montegriffo, P. |author22=Ragaini, S. |author23=Schuster, W. |author24=Trager, S. |author25=Vilardell, F. |author26=Voss, H. |date=2012 |title=The Gaia spectrophotometric standard stars survey – I. Preliminary results |journal=Monthly Notices of the Royal Astronomical Society |volume=426 |issue=3 |pages=1767–81 |doi=10.1111/j.1365-2966.2012.21766.x |bibcode=2012MNRAS.426.1767P|arxiv = 1207.6042 |s2cid=27564967 }}</ref> Its distance has been calculated to be 26 light-years,<ref>{{cite journal |last=Sion |first=Edward M. |date=2009 |title=1.The White Dwarfs Within 20 Parsecs of the Sun: Kinematics and Statistics |journal=The Astronomical Journal |volume=138 |issue=6 |pages=1681–89 |doi=10.1088/0004-6256/138/6/1681 |arxiv=0910.1288 |bibcode=2009AJ....138.1681S|s2cid=119284418 }}</ref> or 28.7 ± 0.5 light-years distant from Earth. It has around 45% of the Sun's mass, yet only 0.15% of its luminosity.<ref name="Subasavage">{{cite journal |author1=Subasavage, John P. |author2=Jao, Wei-Chun |author3=Henry, Todd J. |author4=Bergeron, P. |author5=Dufour, P. |author6=Ianna, Philip A. |author7=Costa, Edgardo |author8=Méndez, René A. |date=2009 |title=The Solar Neighborhood. XXI. Parallax Results from the CTIOPI 0.9&nbsp;m Program: 20 New Members of the 25 Parsec White Dwarf Sample |journal=The Astronomical Journal |volume=137 |issue=6 |pages=4547–60 |doi=10.1088/0004-6256/137/6/4547 |bibcode=2009AJ....137.4547S|arxiv = 0902.0627 |s2cid=14696597 }}</ref><!-- cites previous 1.5 sentences --> WISEPC J083641.12-185947.2 is a [[Astronomy:Brown dwarf|brown dwarf]] of [[Astronomy:Brown dwarf#Spectral class T|spectral type T8p]] located around 72 light-years from Earth. Discovered by infrared astronomy in 2011, it has a magnitude of 18.79.<ref name="Kirkpatrick2012">{{cite journal |last1=Kirkpatrick |first1=J. Davy |last2=Gelino |first2=Christopher R. |last3=Cushing |first3=Michael C. |last4=Mace |first4=Gregory N. |last5=Griffith |first5=Roger L. |last6=Skrutskie |first6=Michael F. |last7=Marsh |first7=Kenneth A. |last8=Wright |first8=Edward L. |last9=Eisenhardt |first9=Peter R. |last10=McLean |first10=Ian S. |last11=Mainzer |first11=Amanda K. |last12=Burgasser |first12=Adam J. |last13=Tinney |first13=C. G. |last14=Parker |first14=Stephen |last15=Salter |first15=Graeme |title=Further Defining Spectral Type "Y" and Exploring the Low-mass End of the Field Brown Dwarf Mass Function |year=2012 |journal=[[Astronomy:The Astrophysical Journal|The Astrophysical Journal]] |volume=753 |issue=2 |pages=156 |arxiv=1205.2122 |doi=10.1088/0004-637X/753/2/156 |bibcode=2012ApJ...753..156K|s2cid=119279752 }}</ref><!-- cites previous two sentences -->

===Planetary systems===
Pyxis is home to three stars with confirmed planetary systems—all discovered by [[Astronomy:Doppler spectroscopy|Doppler spectroscopy]]. A [[Astronomy:Hot Jupiter|hot Jupiter]], [[Astronomy:HD 73256 b|HD 73256 b]], that orbits [[Astronomy:HD 73256|HD 73256]] every 2.55 days, was discovered using the CORALIE spectrograph in 2003. The host star is a yellow star of spectral type G9V that has 69% of our Sun's luminosity, 89% of its diameter and 105% of its mass. Around 119 light-years away, it shines with an apparent magnitude of 8.08 and is around a billion years old.<ref name="Udry2003">{{cite journal |title=The CORALIE survey for southern extra-solar planets X. A Hot Jupiter orbiting HD 73256 |last1=Udry |first1=S. |last2=Mayor |first2=M. |last3=Clausen |first3=J. V. |last4=Freyhammer |first4=L. M. |last5=Helt |first5=B. E. |last6=Lovis |first6=C. |last7=Naef |first7=D. |last8=Olsen |first8=E. H. |last9=Pepe |first9=F. |journal=Astronomy and Astrophysics |volume=407 |issue=2 |pages=679–84 |year=2003 |arxiv=astro-ph/0304248 |bibcode=2003A&A...407..679U |doi=10.1051/0004-6361:20030815|s2cid=118889984 }}</ref> [[Astronomy:HD 73267 b|HD 73267 b]] was discovered with the [[Astronomy:High Accuracy Radial Velocity Planet Searcher|High Accuracy Radial Velocity Planet Searcher]] (HARPS) in 2008. It orbits [[Astronomy:HD 73267|HD 73267]] every 1260 days, a 7 billion-year-old star of spectral type G5V that is around 89% as massive as the Sun.<ref name="Moutou2009">{{cite journal |title=The HARPS search for southern extra-solar planets XVII. Six long-period giant planets around BD −17 0063, HD 20868, HD 73267, HD 131664, HD 145377, HD 153950 |url=http://www.aanda.org/articles/aa/full_html/2009/11/aa10941-08/aa10941-08.html |last1=Moutou |first1=C. |last2=Mayor |first2=M. |last3=Lo Curto |first3=G. |last4=Udry |first4=S. |last5=Bouchy |first5=F. |last6=Benz |first6=W. |last7=Lovis |first7=C. |last8=Naef |first8=D. |last9=Pepe |first9=F. |last10=Queloz |first10=D. |last11=Santos |first11=N. C. |journal=Astronomy and Astrophysics |volume=496 |issue=2 |pages=513–19 |date=2009 |arxiv=0810.4662 |bibcode=2009A&A...496..513M |doi=10.1051/0004-6361:200810941|s2cid=116707055 }}</ref> A [[Astronomy:Red dwarf|red dwarf]] of spectral type M2.5V that has around 42% the Sun's mass, [[Astronomy:Gliese 317|Gliese 317]] is orbited by two gas giant planets. Around 50 light-years distant from Earth, it is a good candidate for future searches for more terrestrial rocky planets.<ref>{{cite journal |title=Astrometry and radial velocities of the planet host M dwarf Gliese 317: new trigonometric distance, metallicity and upper limit to the mass of Gliese 317 b |last1=Anglada-Escude |first1=Guillem |last2=Boss |first2=Alan P. |last3=Weinberger |first3=Alycia J. |last4=Thompson |first4=Ian B. |last5=Butler |first5=R. Paul |last6=Vogt |first6=Steven S. |last7=Rivera |first7=Eugenio J. |journal=The Astrophysical Journal |date=2012 |volume=764 |issue=1 |pages=37A |bibcode=2012ApJ...746...37A |doi=10.1088/0004-637X/746/1/37 |arxiv=1111.2623|s2cid=118526264 }}</ref>

===Deep sky objects===
[[File:NGC 2818 by the Hubble Space Telescope.jpg|thumb|right|The planetary nebula NGC 2818, imaged by the Hubble telescope|alt=A coloured oval cloud of material against a dark background]]
Pyxis lies in the [[Astronomy:Galactic plane|plane]] of the [[Astronomy:Milky Way|Milky Way]], although part of the eastern edge is dark, with material obscuring our galaxy arm there. [[Astronomy:NGC 2818|NGC 2818]] is a [[Astronomy:Planetary nebula|planetary nebula]] that lies within a dim [[Astronomy:Open cluster|open cluster]] of magnitude 8.2.<ref>{{cite book |last=Inglis |first=Mike |title=Astronomy of the Milky Way: Observer's Guide to the Southern Sky |publisher=Springer |location=New York, New York |date=2004 |isbn=1-85233-742-7 |url=https://books.google.com/books?id=1r0qvMjSCGAC&pg=SA3-PA31}}</ref> NGC 2818A is an [[Astronomy:Open cluster|open cluster]] that lies on line of sight with it.<ref name=inglisOC/> [[Astronomy:K 1-2|K 1-2]] is a planetary nebula whose central star is a [[Astronomy:Spectroscopic binary|spectroscopic binary]] composed of two stars in close orbit with [[Astronomy:Astrophysical jet|jets]] emanating from the system. The surface temperature of one component has been estimated at as high as 85,000&nbsp;K.<ref name="Exter 2003">{{cite journal |title=The planetary nebula K 1-2 and its binary central star VW Pyx |author1=Exter, K. M. |author2=Pollacco, D. L. |author3=Bell, S. A. |journal=Monthly Notices of the Royal Astronomical Society |volume=341 |issue=4 |pages=1349–59 |year=2003 |doi=10.1046/j.1365-8711.2003.06505.x |bibcode=2003MNRAS.341.1349E|url=https://academic.oup.com/mnras/article-pdf/341/4/1349/3501479/341-4-1349.pdf |doi-access=free }}</ref> [[Astronomy:NGC 2627|NGC 2627]] is an [[Astronomy:Open cluster|open cluster]] of magnitude 8.4 that is visible in binoculars.<ref name="inglisOC">{{cite book |last=Inglis |first=Mike |title=Observer's Guide to Star Clusters |publisher=Springer Science & Business Media |location=New York, New York |date=2013 |pages=202–03 |isbn=978-1-4614-7567-5 |url=https://books.google.com/books?id=ewHABAAAQBAJ&pg=PA202}}</ref>

Discovered in 1995,<ref name="Irwin 1995">{{cite journal |title=The PYXIS Cluster: A Newly Identified Galactic Globular Cluster |author1=Irwin, M. J. |author2=Demers, Serge |author3=Kunkel, W. E. |journal=Astrophysical Journal Letters |volume=453 |page=L21 |year=1995 |doi=10.1086/513301 |bibcode=1995ApJ...453L..21I|doi-access=free }}</ref> the [[Astronomy:Pyxis globular cluster|Pyxis globular cluster]] is a 13.3 ± 1.3 billion year-old [[Astronomy:Globular cluster|globular cluster]] situated around 130,000 light-years distant from Earth and around 133,000 light-years distant from the centre of the Milky Way—a region not previously thought to contain globular clusters.<ref name="1996AJ....112.2013S">{{cite journal |title=Deep Photometry of the Outer Halo Globular Cluster in PYXIS |author1=Sarajedini, Ata |author2=Geisler, Doug |journal=Astronomical Journal |volume=112 |year=1996 |page=2013 |doi=10.1086/118159 |bibcode=1996AJ....112.2013S|doi-access=free }}</ref> Located in the [[Astronomy:Galactic halo|galactic halo]], it was noted to lie on the same plane as the [[Astronomy:Large Magellanic Cloud|Large Magellanic Cloud]] and the possibility has been raised that it might be an escaped object from that galaxy.<ref name="Irwin 1995"/>

[[Astronomy:NGC 2613|NGC 2613]] is a spiral galaxy of magnitude 10.5 which appears spindle-shaped as it is almost edge-on to observers on Earth.<ref>{{cite book |first=Stephen James |last=O'Meara |title=Steve O'Meara's Herschel 400 Observing Guide |publisher=Cambridge University Press |location=Cambridge, United Kingdom |date=2007 |isbn=978-0-521-85893-9 |url=https://books.google.com/books?id=Nyh9fAC_tpIC&pg=PA82}}</ref> Henize 2-10 is a dwarf galaxy which lies 30 million light-years away. It has a black hole of around a million solar masses at its centre. Known as a [[Astronomy:Starburst galaxy|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.<ref>{{cite web |title=Henize 2–10: A Surprisingly Close Look at the Early Cosmos |work=Chandra X-Ray Observatory |publisher=NASA |url=http://chandra.harvard.edu/photo/2011/he210/ |access-date=6 October 2012}}</ref>

== See also ==
* Pyxis (Chinese astronomy)

== Notes ==
{{notelist}}

==References==
{{Reflist}}

{{Commons|Pyxis}}
{{Stars of Pyxis}}
{{navconstel}}
{{ConstellationsByLacaille}}

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[[Category:Southern constellations]]
[[Category:Constellations listed by Lacaille]]

{{Sourceattribution|Pyxis}}