Editing Grus (constellation)

{{short description|Constellation in the southern celestial hemisphere}}
{{featured article}}
{{use British English|date=February 2015}}
{{Infobox constellation
| name = Grus
| abbreviation = Gru
| genitive = Gruis
| pronounce = {{IPAc-en|ˈ|ɡ|r|ʌ|s}}, or colloquially {{IPAc-en|ˈ|ɡ|r|uː|s}}; genitive {{IPAc-en|ˈ|ɡ|r|uː|ᵻ|s}}
| symbolism = the [[Crane (bird)|crane]]
| RA = {{RA|21|27.4}} to {{RA|23|27.1}}<ref name="boundary"/>
| dec= −36.31° to −56.39°<ref name="boundary"/>
| family = [[Bayer Family|Bayer]]
| quadrant = SQ4
| areatotal = 366
| arearank = 45th
| numbermainstars = 8
| numberbfstars = 28
| numberstarsplanets = 6
| numberbrightstars = 3
| numbernearbystars = 1
| brighteststarname = [[Alpha Gruis|α Gru]] (Alnair)
| starmagnitude = 1.73
| neareststarname = [[Gliese 832]]
| stardistancely = 16.11
| stardistancepc = 4.94
| numbermessierobjects = 0
| meteorshowers = 0
| bordering = [[Piscis Austrinus]]<br />[[Microscopium]]<br />[[Indus (constellation)|Indus]]<br />[[Tucana]]<br />[[Phoenix (constellation)|Phoenix]]<br />[[Sculptor (constellation)|Sculptor]]
| latmax = [[34th parallel north|34]]
| latmin = [[90th parallel south|90]]
| month = October
| notes=}}

'''Grus''' ({{IPAc-en|ˈ|ɡ|r|ʌ|s}}, or colloquially {{IPAc-en|ˈ|ɡ|r|uː|s}}) is a [[constellation]] in the [[southern sky]]. Its name is [[Latin]] for the [[crane (bird)|crane]], a type of bird. It is one of twelve constellations conceived by [[Petrus Plancius]] from the observations of [[Pieter Dirkszoon Keyser]] and [[Frederick de Houtman]]. Grus first appeared on a {{Convert|35|cm|in|-diameter|abbr=off|adj=mid}} celestial globe published in 1598 in Amsterdam by Plancius and [[Jodocus Hondius]] and was depicted in [[Johann Bayer]]'s star atlas ''[[Uranometria]]'' of 1603. French explorer and astronomer [[Nicolas-Louis de Lacaille]] gave [[Bayer designation]]s to its stars in 1756, some of which had been previously considered part of the neighbouring constellation [[Piscis Austrinus]]. The constellations Grus, [[Pavo (constellation)|Pavo]], [[Phoenix (constellation)|Phoenix]] and [[Tucana]] are collectively known as the "Southern Birds".

The constellation's brightest star, [[Alpha Gruis]], is also known as Alnair and appears as a 1.7-[[Apparent magnitude|magnitude]] blue-white star. [[Beta Gruis]] is a [[red giant]] [[variable star]] with a minimum magnitude of 2.3 and a maximum magnitude of 2.0. Six star systems have been found to have [[exoplanet|planets]]: the red dwarf [[Gliese 832]] is one of the closest stars to Earth to have a planetary system. Another—[[WASP-95]]—has a planet that orbits every two days. [[Deep-sky object]]s found in Grus include the [[planetary nebula]] [[IC 5148]], also known as the Spare Tyre Nebula, and a group of four interacting galaxies known as the Grus Quartet.

==History==

[[File:Grus and Piscis Austrinus from Atlas Coelestis.jpg|thumbnail|left|The constellations Grus and [[Piscis Austrinus]], which once formed a single constellation, as depicted in ''Atlas Coelestis'' by [[Johann Doppelmayr]], ca. 1742]]
[[File:Johann Bayer - Uraniometria - Southern Birds.jpg|thumb|left|The "southern birds", as depicted in [[Johann Bayer]]'s ''[[Uranometria]]'']]
The stars that form Grus were originally considered part of the neighbouring constellation [[Piscis Austrinus]] (the southern fish), with [[Gamma Gruis]] seen as part of the fish's tail.<ref name=tiriongrus>{{cite web| url=http://www.ianridpath.com/startales/grus.html | title=Grus | work= Star Tales |author=Ridpath, Ian|publisher=self-published | access-date= 8 February 2014| author-link=Ian Ridpath }}</ref> The stars were first defined as a separate constellation by the astronomer [[Petrus Plancius]], who created twelve new constellations based on the observations of the southern sky by the Dutch explorers [[Pieter Dirkszoon Keyser]] and [[Frederick de Houtman]], who had sailed on the first Dutch trading expedition, known as the ''[[First Dutch Expedition to Indonesia|Eerste Schipvaart]]'', to the [[East Indies]]. Grus first appeared on a 35-centimetre-diameter celestial globe published in 1598 in [[Amsterdam]] by Plancius with [[Jodocus Hondius]]. Its first depiction in a celestial atlas was in the German cartographer [[Johann Bayer]]'s ''[[Uranometria]]'' of 1603.<ref>{{cite web| url=http://www.ianridpath.com/startales/bayer-southern.html | title=Bayer's Southern Star Chart | work= Star Tales |author=Ridpath, Ian|publisher=self-published | access-date= 18 August 2013}}</ref> De Houtman included it in his southern star catalogue the same year under the Dutch name ''Den Reygher'', "The Heron",<ref>{{cite web| url=http://www.ianridpath.com/startales/startales1c.html#houtman | title=Frederick de Houtman's catalogue| work= Star Tales |author=Ridpath, Ian|publisher=self-published | access-date= 15 August 2013}}</ref> but Bayer followed Plancius and Hondius in using Grus.<ref name=tiriongrus/>

An alternative name for the constellation, ''Phoenicopterus'' (Latin "[[flamingo]]"), was used briefly during the early 17th century, seen in the 1605 work ''Cosmographiae Generalis'' by Paul Merula of [[Leiden University]] and a c. 1625 globe by Dutch globe maker Pieter van den Keere. Astronomer Ian Ridpath has reported the symbolism likely came from Plancius originally, who had worked with both of these people.<ref name=tiriongrus/> Grus and the nearby constellations [[Phoenix (constellation)|Phoenix]], [[Tucana]] and [[Pavo (constellation)|Pavo]] are collectively called the "Southern Birds".<ref name="binocs">{{cite book|last=Moore|first=Patrick|author-link=Patrick Moore|title=Exploring the Night Sky with Binoculars|publisher=Cambridge University Press|location=Cambridge, United Kingdom |date=2000|page=[https://archive.org/details/exploringnightsk00moor/page/48 48]|isbn=978-0-521-79390-2|url=https://archive.org/details/exploringnightsk00moor|url-access=registration}}</ref>

The stars that correspond to Grus were generally too far south to be seen from China. In [[Chinese astronomy]], Gamma and [[Lambda Gruis]] may have been included in the tub-shaped asterism ''Bàijiù'', along with stars from Piscis Austrinus.<ref name=tiriongrus/> In Central Australia, the [[Upper Arrernte language|Arrernte]] and [[Luritja dialect|Luritja]] people living on a mission in [[Hermannsburg, Northern Territory|Hermannsburg]] viewed the sky as divided between them, east of the [[Milky Way]] representing Arrernte camps and west denoting Luritja camps. [[Alpha Gruis|Alpha]] and [[Beta Gruis]], along with [[Fomalhaut]], [[Alpha Pavonis]] and the stars of [[Musca]], were all claimed by the Arrernte.<ref name="noctuary">{{cite book|last=Johnson|first=Diane|title=Night Skies of Aboriginal Australia: a Noctuary|publisher=University of Sydney|location=Darlington, New South Wales|date=1998|pages=[https://archive.org/details/nightskiesofabor0000john/page/70 70–72]|isbn=1-86451-356-X|url-access=registration|url=https://archive.org/details/nightskiesofabor0000john/page/70}}</ref>

==Characteristics==
Grus is bordered by Piscis Austrinus to the north, [[Sculptor (constellation)|Sculptor]] to the northeast, Phoenix to the east, Tucana to the south, [[Indus (constellation)|Indus]] to the southwest, and [[Microscopium]] to the west. Bayer straightened the tail of Piscis Austrinus to make way for Grus in his ''Uranometria''.<ref name=tiriongrus/> Covering 366 square degrees, it ranks 45th of the 88 [[Lists of constellations|modern constellations]] in size and covers 0.887% of the night sky.<ref name=bagnall>{{cite book |last=Bagnall |first=Philip M. |title=The Star Atlas Companion: What You Need to Know about the Constellations |publisher=Springer  |location=New York, New York |date=2012 |isbn=978-1-4614-0830-7 |page=232 |url=https://books.google.com/books?id=KcIg02TKW6QC&q=Grus+45th+366&pg=PA232}}</ref> The three-letter abbreviation for the constellation, as adopted by the [[International Astronomical Union]] in 1922, is "Gru".<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 (US magazine)|Popular Astronomy]] | volume=30 | page=469 | bibcode=1922PA.....30..469R | date=1922 }}</ref> The official constellation boundaries, as set by Belgian astronomer [[Eugène Joseph Delporte|Eugène Delporte]] in 1930, are defined as a polygon of 6 segments. In the [[equatorial coordinate system]], the [[right ascension]] coordinates of these borders lie between {{RA|21|27.4}} and {{RA|23|27.1}}, while the [[declination]] coordinates are between −36.31° and −56.39°.<ref name="boundary">{{Cite journal | title=Grus, Constellation Boundary | journal=The Constellations | publisher=International Astronomical Union | url=http://www.iau.org/public/constellations/#gru | access-date=19 November 2013 }}</ref> Grus is located too far south to be seen by observers in the British Isles and the northern United States, though it can easily be seen from [[Florida]] or [[San Diego]];<ref name="moore01">{{cite book|last=Moore|first=Patrick|title=Stargazing: Astronomy Without a Telescope|publisher=Cambridge University Press|location=Cambridge, United Kingdom|date=2001|page=[https://archive.org/details/stargazingastron00moor/page/99 99]|isbn=0-521-79445-5|url=https://archive.org/details/stargazingastron00moor|url-access=registration|quote=Grus constellation visibility.}}</ref> the whole constellation is visible to observers south of latitude [[33rd parallel north|33°N]].<ref name=tirionconst>{{cite web| url=http://www.ianridpath.com/constellations1.html | title=Constellations: Andromeda–Indus | work= Star Tales |author=Ridpath, Ian|publisher=self-published | access-date= 1 April 2014}}</ref>{{efn|1=While parts of the constellation technically rise above the horizon to observers between 33°N and [[53rd parallel north|53°N]], stars within a few degrees of the horizon are to all intents and purposes unobservable.<ref name=tirionconst/>}}

==Features==

===Stars===
{{see also|List of stars in Grus}}
[[Image:Constellation Grus.jpg|thumb|250px|The constellation Grus as it can be seen by the naked eye]]
Keyser and de Houtman assigned twelve stars to the constellation.<ref name=knobel>{{cite journal | title = On Frederick de Houtman's Catalogue of Southern Stars, and the Origin of the Southern Constellations | author= Knobel, Edward B. |journal = [[Monthly Notices of the Royal Astronomical Society]] | volume= 77| issue= 5 | pages=414–32 [430] | bibcode = 1917MNRAS..77..414K |date=1917 | doi=10.1093/mnras/77.5.414| author-link= Edward Knobel | doi-access= free }}</ref> Bayer depicted Grus on his chart, but did not assign its stars [[Bayer designation]]s. French explorer and astronomer [[Nicolas-Louis de Lacaille]] labelled them Alpha to Phi in 1756 with some omissions. In 1879, American astronomer [[Benjamin Apthorp Gould|Benjamin Gould]] added Kappa, Nu, Omicron and Xi, which had all been catalogued by Lacaille but not given Bayer designations. Lacaille considered them too faint, while Gould thought otherwise. Xi Gruis had originally been placed in Microscopium. Conversely, Gould dropped Lacaille's Sigma as he thought it was too dim.<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=360–62}}</ref><!-- cites previous three sentences -->

Grus has several bright stars. Marking the left wing is Alpha Gruis,<ref name=knobel/> a blue-white star of spectral type B6V and [[apparent magnitude]] 1.7, around 101 [[light-year]]s from Earth.<ref>{{cite web |url = http://simbad.u-strasbg.fr/simbad/sim-id?Ident=Alpha+Gru&NbIdent=1&Radius=2&Radius.unit=arcmin&submit=submit+id |title = Alpha Gruis – High Proper-motion Star |work = SIMBAD Astronomical Database|publisher=Centre de Données astronomiques de Strasbourg |access-date = 1 December 2013}}</ref> Its traditional name, Alnair, means "the bright one" and refers to its status as the brightest star in Grus (although the Arabians saw it as the brightest star in the Fish's tail, as Grus was then depicted).[http://www.constellationsofwords.com/stars/Alnair.html Alnair] Alnair is around 380 times as [[luminosity|luminous]] and has over 3 times the diameter of the [[Sun]].<ref name="kaleralpha">{{cite web|url=http://stars.astro.illinois.edu/sow/alnair.html |title=Al Nair |last=Kaler|first=James B|author-link=James B. Kaler|work=Stars|publisher=University of Illinois|access-date= 1 December 2013}}</ref> Lying 5 degrees west of Alnair,<ref name="motz"/> denoting the Crane's heart is Beta Gruis<ref name=knobel/> (the proper name is Tiaki<ref name="IAU-LSN">{{cite web | url=https://www.iau.org/public/themes/naming_stars/ | title=Naming Stars |publisher=IAU.org |access-date=30 July 2018}}</ref>), a [[red giant]] of spectral type M5III.<ref>{{cite web |url = http://simbad.u-strasbg.fr/simbad/sim-id?Ident=Beta+Gru&NbIdent=1&Radius=2&Radius.unit=arcmin&submit=submit+id |title = Beta Gruis – Pulsating Variable Star |work = SIMBAD Astronomical Database|publisher=Centre de Données astronomiques de Strasbourg |access-date = 1 December 2013}}</ref> It has a diameter of 0.8 [[astronomical unit]]s (AU) (if placed in the Solar System it would extend to the orbit of Venus) located around 170 light-years from Earth. It is a [[variable star]] with a minimum magnitude of 2.3 and a maximum magnitude of 2.0.<ref name="kalerbeta">{{cite web|url=http://stars.astro.illinois.edu/sow/betagru.html |title=Beta Gruis |last=Kaler|first=James B|author-link=James B. Kaler|work=Stars|publisher=University of Illinois|access-date= 1 December 2013}}</ref> An imaginary line drawn from the Great Square of [[Pegasus (constellation)|Pegasus]] through Fomalhaut will lead to Alnair and Beta Gruis.<ref name="moore01"/>

Lying in the northwest corner of the constellation and marking the crane's eye is Gamma Gruis,<ref name="motz">{{cite book|last=Motz|first=Lloyd|author2=Nathanson, Carol|title=The Constellations: An Enthusiast's Guide to the Night Sky|publisher=Aurum Press|location=London, United Kingdom|date=1991|page=370|isbn=978-1-85410-088-7}}</ref> a blue-white [[subgiant]] of spectral type B8III and magnitude 3.0 lying around 211 light-years from Earth.<ref>{{cite web |url = http://simbad.u-strasbg.fr/simbad/sim-id?Ident=GAmma+Gruis&NbIdent=1&Radius=2&Radius.unit=arcmin&submit=submit+id |title = Gamma Gruis |work = SIMBAD Astronomical Database|publisher=Centre de Données astronomiques de Strasbourg |access-date = 4 December 2013}}</ref> Also known as Al Dhanab,<ref name="IAU-LSN"/> it has finished fusing its core hydrogen and has begun cooling and expanding, which will see it transform into a red giant.<ref name="kalergamma">{{cite web|url=http://stars.astro.illinois.edu/sow/aldhanab.html |title=Al Dhanab |last=Kaler|first=James B|author-link=James B. Kaler|work=Stars|publisher=University of Illinois|access-date= 4 December 2013}}</ref>

There are several [[double star]]s visible to the naked eye in Grus. Forming a triangle with Alnair and Beta, Delta Gruis is an optical double whose components—[[Delta1 Gruis|Delta<sup>1</sup>]] and [[Delta2 Gruis|Delta<sup>2</sup>]]—are separated by 45 arcseconds.<ref name="motz"/> Delta<sup>1</sup> is a [[yellow giant]] of spectral type G7III and magnitude 4.0, 309 light-years from Earth,<ref>{{cite web |url = http://simbad.u-strasbg.fr/simbad/sim-id?Ident=del1+gru&NbIdent=1&Radius=2&Radius.unit=arcmin&submit=submit+id |title = HR 8556 – Star in double system |work = SIMBAD Astronomical Database|publisher=Centre de Données astronomiques de Strasbourg |access-date = 19 January 2014}}</ref> and may have its own magnitude 12 [[K-type main-sequence star|orange dwarf]] companion.<ref name="kalerdelta">{{cite web|url=http://stars.astro.illinois.edu/sow/deltagru.html |title=Delta Gruis |last=Kaler|first=James B|author-link=James B. Kaler|work=Stars|publisher=University of Illinois|access-date= 26 January 2014}}</ref> Delta<sup>2</sup> is a red giant of spectral type M4.5III and semiregular variable that ranges between magnitudes 3.99 and 4.2,<ref name=AAVSOdel2>{{cite web|url=http://www.aavso.org/vsx/index.php?view=detail.top&oid=14810 |title=Delta 2 Gruis |author=Watson, Christopher|date=25 August 2009|work=AAVSO Website|publisher=American Association of Variable Star Observers|access-date=18 January 2014}}</ref> located 325 light-years from Earth. It has around 3 times the mass and 135 times the diameter of the Sun.<ref name="kalerdelta"/> Mu Gruis, composed of [[Mu1 Gruis|Mu<sup>1</sup>]] and [[Mu2 Gruis|Mu<sup>2</sup>]], is also an optical double—both stars are yellow giants of spectral type G8III around 2.5 times as massive as the Sun with surface temperatures of around 4900 K.<ref name="kalermu">{{cite web|url=http://stars.astro.illinois.edu/sow/mugru.html |title=Mu Gruis |last=Kaler|first=James B|author-link=James B. Kaler|work=Stars|publisher=University of Illinois|access-date= 26 January 2014}}</ref> Mu<sup>1</sup> is the brighter of the two at magnitude 4.8 located around 275 light-years from Earth,<ref>{{cite web |url = http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=HR+8486&submit=SIMBAD+search |title = HR 8486 |work = SIMBAD Astronomical Database |publisher = Centre de Données astronomiques de Strasbourg |access-date = 19 January 2014}}</ref> while Mu<sup>2</sup> the dimmer at magnitude 5.11 lies 265 light-years distant from Earth.<ref>{{cite web |url = http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=HR+8488&submit=SIMBAD+search |title = HR 8488 |work = SIMBAD Astronomical Database |publisher = Centre de Données astronomiques de Strasbourg |access-date = 19 January 2014}}</ref> Pi Gruis, an optical double with a variable component, is composed of [[Pi1 Gruis|Pi<sup>1</sup> Gruis]] and [[Pi2 Gruis|Pi<sup>2</sup>]]. Pi<sup>1</sup> is a [[semiregular variable star|semi-regular]] red giant of spectral type S5, ranging from magnitude 5.31 to 7.01 over a period of 191 days,<ref name=AAVSOpi1>{{cite web|url=http://www.aavso.org/vsx/index.php?view=detail.top&oid=14811 |title=Pi 1 Gruis |author =Otero, Sebastian Alberto|date=20 June 2011 |work=AAVSO Website|publisher=American Association of Variable Star Observers|access-date=19 January 2014}}</ref> and is around 532 light-years from Earth.<ref>{{cite web |url =http://simbad.u-strasbg.fr/simbad/sim-id?Ident=Pi1+Gru&NbIdent=1&Radius=2&Radius.unit=arcmin&submit=submit+id |title = Pi1 Gruis – S Star |work = SIMBAD Astronomical Database|publisher=Centre de Données astronomiques de Strasbourg |access-date = 19 January 2014}}</ref> One of the brightest S-class stars to Earth viewers, it has a companion star of apparent magnitude 10.9 with sunlike properties, being a [[G-type main-sequence star|yellow main sequence star]] of spectral type G0V. The pair make up a likely binary system.<ref>{{cite journal|author1=Sacuto, S. |author2=Jorissen, A. |author3=Cruzalèbes, P. |author4=Chesneau, O. |author5=Ohnaka, K. |author6=Quirrenbach, A. |author7=Lopez, B. |date=2008|title=The close circumstellar environment of the semi-regular S-type star π 1 Gruis|journal=Astronomy & Astrophysics|volume=482|issue=2|pages=561–74| bibcode=2008A&A...482..561S|arxiv = 0803.3077 |doi = 10.1051/0004-6361:20078306 |s2cid=14085392 |url=http://hal.archives-ouvertes.fr/docs/00/26/60/23/PDF/8306.pdf |archive-url=https://web.archive.org/web/20110513023213/http://hal.archives-ouvertes.fr/docs/00/26/60/23/PDF/8306.pdf |archive-date=2011-05-13 |url-status=live}}</ref> Pi<sup>2</sup> is a [[giant star]] of spectral type F3III-IV located around 130 light-years from Earth,<ref>{{cite web |url =http://simbad.u-strasbg.fr/simbad/sim-id?Ident=Pi2+Gru&NbIdent=1&Radius=2&Radius.unit=arcmin&submit=submit+id |title = LTT 8994 – High proper-motion Star |work = SIMBAD Astronomical Database|publisher=Centre de Données astronomiques de Strasbourg |access-date = 19 January 2014}}</ref> and is often brighter than its companion at magnitude 5.6.{{sfn|Ridpath|Tirion|2001|pp=152–53}} Marking the right wing is [[Theta Gruis]],<ref name=knobel/> yet another double star, lying 5 degrees east of Delta<sup>1</sup> and Delta<sup>2</sup>.<ref name="motz"/>

[[RZ Gruis]] is a binary system of apparent magnitude 12.3 with occasional dimming to 13.4, whose components—a [[white dwarf]] and [[main sequence]] star—are thought to orbit each other roughly every 8.5 to 10 hours. It belongs to the UX Ursae Majoris subgroup of [[cataclysmic variable star]] systems, where material from the donor star is drawn to the white dwarf where it forms an [[accretion disc]] that remains bright and outshines the two component stars. The system is poorly understood,<ref>{{cite journal|author1=Bisol, Alexandra C. |author2=Godon, Patrick |author3=Sion, Edward M. |date=2012|title=Far Ultraviolet Spectroscopy of Three Long Period Nova-Like Variables|journal=Publications of the Astronomical Society of the Pacific|volume=124|issue=912|pages=158–63|bibcode=2012PASP..124..158B|arxiv = 1112.3711 |doi = 10.1086/664464 |s2cid=116536811 }}</ref> though the donor star has been calculated to be of spectral type F5V.<ref>{{cite journal|author1=Stickland, D.J. |author2=Kelly, B.D. |author3=Cooke, J.A. |author4=Coulson, I. |author5=Engelbrecht, C. |author6=Kilkenny, D. |date=1984|title=RZ Gru – A UX UMa 'disc star'|journal=Monthly Notices of the Royal Astronomical Society|volume=206|issue=4 |pages= 819–31|bibcode=1984MNRAS.206..819S|doi=10.1093/mnras/206.4.819|doi-access=free}}</ref> These stars have spectra very similar to novae that have returned to quiescence after outbursts, yet they have not been observed to have erupted themselves. The [[American Association of Variable Star Observers]] recommends watching them for future events.<ref>{{cite web|url=http://www.aavso.org/vsots_uxuma|title=UX Ursae Majoris|last=Malatesta|first=Kerri|date=17 July 2010 |work=Variable Star of the Season|access-date=26 January 2014}}</ref><!-- cites previous two sentences --> [[CE Gruis]] (also known as Grus V-1) is a faint (magnitude 18–21) star system also composed of a white dwarf and donor star; in this case the two are so close they are [[Tidal locking|tidally locked]]. Known as [[Polar (cataclysmic variable star)|polars]], material from the donor star does not form an accretion disc around the white dwarf, but rather streams directly onto it.<ref name="ramsay02">{{cite journal|author1=Ramsay, Gavin |author2=Cropper, Mark |date=2002|title=First X-ray Observations of the Polar CE Gru|journal=Monthly Notices of the Royal Astronomical Society|volume=335|issue=4|pages=918–22|bibcode=2002MNRAS.335..918R|arxiv = astro-ph/0205102 |doi = 10.1046/j.1365-8711.2002.05666.x |doi-access=free |s2cid=8460918 }}</ref>

Six star systems are thought to have planetary systems. [[Tau1 Gruis|Tau<sup>1</sup> Gruis]] is a yellow star of magnitude 6.0 located around 106 light-years away.<ref>{{cite web |url = http://simbad.u-strasbg.fr/simbad/sim-id?Ident=tau1+gru&NbIdent=1&Radius=2&Radius.unit=arcmin&submit=submit+id |title = Tau1 Gruis -- High proper-motion Star |work = SIMBAD Astronomical Database|publisher=Centre de Données astronomiques de Strasbourg |access-date = 11 February 2014}}</ref> It may be a main sequence star or be just beginning to depart from the sequence as it expands and cools. In 2002 the star was found to have a planetary companion.<ref name="Jones2003">{{cite journal | title=An Exoplanet in Orbit around τ1 Gruis | last1=Jones | first1=R. Paul | last2=Butler | first2=Hugh R. A. | last3=Tinney | first3=C. G. | last4=Marcy | first4=Geoffrey W. | last5=Penny | first5=Alan J. | last6=McCarthy | first6=Chris | last7=Carter | first7=Brad D. | journal=Monthly Notices of the Royal Astronomical Society | date=2003 | volume=341 | issue=3 | pages=948–52 | arxiv=astro-ph/0209302 | bibcode=2003MNRAS.341..948J | doi=10.1046/j.1365-8711.2003.06481.x| doi-access=free | s2cid=1575040 }}</ref> [[HD 215456]], [[HD 213240]] and [[WASP-95]] are yellow sunlike stars discovered to have two planets,<ref>{{cite arXiv |last1=Mayor |first1=M. |last2=Marmier |first2=M. |last3=Lovis |first3=C. |last4=Udry |first4=S. |last5=Ségransan |first5=D. |last6=Pepe |first6=F. |last7=Benz |first7=W. |last8=Bertaux |first8=J.-L. |last9=Bouchy |first9=F. |last10=Dumusque |first10=X. |last11=Lo Curto |first11=G. |last12=Mordasini |first12=C. |last13=Queloz |first13=D. |last14=Santos |first14=N.C. |display-authors=1
 |date=2011 |title=The HARPS Search for Southern Extra-solar Planets XXXIV. Occurrence, Mass Distribution and Orbital Properties of Super-Earths and Neptune-mass Planets |eprint=1109.2497 |class=astro-ph.EP}}</ref> a planet and a remote [[red dwarf]],<ref name=mugrauer>{{cite journal | last1=Mugrauer |first1=M. | last2=Neuhäuser | first2=R. | last3=Seifahrt | first3=A. | last4=Mazeh | first4=T. | last5=Guenther | first5=E. | title=Four New Wide Binaries Among Exoplanet Host Stars | journal=[[Astronomy and Astrophysics]] |date=2005 |volume=440 | issue=3 |pages=1051–60 | doi=10.1051/0004-6361:20042297 | bibcode=2005A&A...440.1051M|arxiv = astro-ph/0507101 |s2cid=14065040 }}</ref> and a [[hot Jupiter]], respectively; this last—WASP-95b—completes an orbit round its sun in a mere two days.<ref name="hellier13">{{cite journal|author1=Hellier, Coel |author2=Anderson, D.R. |author3=Collier Cameron, A. |author4=Delrez, L. |author5=Gillon, M. |author6=Jehin, E. |author7=Lendl, M. |author8=Maxted, P.F.L. |author9=Pepe, F. |author10=Pollacco, D. |author11=Queloz, D. |author12=Segransan, D. |author13=Smalley, B. |author14=Smith, A.M.S. |author15=Southworth, J. |author16=Triaud, A.H.M.J. |author17=Udry, S. |author18=West, R.G. |date=2014|title=Transiting Hot Jupiters from WASP-South, Euler and TRAPPIST: WASP-95b to WASP-101b|bibcode=2014MNRAS.440.1982H|arxiv=1310.5630|doi=10.1093/mnras/stu410|journal=Monthly Notices of the Royal Astronomical Society |volume=440 |issue=3 |pages=1982–92|doi-access=free |s2cid=54977201 }}</ref> [[Gliese 832]] is a red dwarf of spectral type M1.5V and apparent magnitude 8.66 located only 16.1 light-years distant; hence it is one of the nearest stars to the Solar System. A [[Jupiter]]-like planet—[[Gliese 832 b]]—orbiting the red dwarf over a period of 9.4±0.4 years was discovered in 2008.<ref name="bailey08">{{cite journal |last1=Bailey |first1=J. |last2=Butler |first2=R.P. |last3=Tinney |first3=C.G. |last4=Jones |first4=H.R.A. |last5=O'Toole |first5=S. |last6=Carter |first6=B.D. |last7=Marcy |first7=G. W. |year=2009|title=A Jupiter-like Planet Orbiting the Nearby M Dwarf GJ832 |journal=[[The Astrophysical Journal]] |volume=690 |issue=1 |pages=743–47 |arxiv=0809.0172 |bibcode=2009ApJ...690..743B |doi=10.1088/0004-637X/690/1/743|s2cid=17172233 }}</ref><!-- cites 2 previous sentences --> [[WISE 2220−3628]] is a [[brown dwarf]] of spectral type Y, and hence one of the coolest star-like objects known. It has been calculated as being around 26 light-years distant from Earth.<ref name="Kirkpatrick2012">{{cite journal |author-link=J. Davy Kirkpatrick |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=Amy K. |last12=Burgasser |first12=Adam J. |last13=Tinney |first13=Chris 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=[[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>

In July 2019, astronomers reported finding a star, [[S5-HVS1]], traveling {{convert|1755|km/s|mph|abbr=on}}, faster that any other star detected so far. The star is in the Grus constellation in the southern sky, and about 29,000 light-years from Earth, and may have been propelled out of the [[Milky Way]] [[galaxy]] after interacting with [[Sagittarius A*]], the [[supermassive black hole]] at the center of the galaxy.<ref name="NYT-20191114">{{cite news |last=Overbye |first=Dennis |author-link=Dennis Overbye |title=A Black Hole Threw a Star Out of the Milky Way Galaxy - So long, S5-HVS1, we hardly knew you. |url=https://www.nytimes.com/2019/11/14/science/stars-black-hole-milky-way.html |archive-url=https://ghostarchive.org/archive/20220102/https://www.nytimes.com/2019/11/14/science/stars-black-hole-milky-way.html |archive-date=2022-01-02 |url-access=limited |url-status=live |date=14 November 2019 |work=[[The New York Times]] |access-date=18 November 2019 }}{{cbignore}}</ref><ref name="MNRAS-20191109">{{cite journal |author=Koposov, Sergey E. |display-authors=et al. |title= Discovery of a nearby 1700 km/s star ejected from the Milky Way by Sgr A*|journal=Monthly Notices of the Royal Astronomical Society |date=11 November 2019 |arxiv=1907.11725 |doi=10.1093/mnras/stz3081 |doi-access=free |s2cid=198968336 }}</ref><ref name="SA-20190731">{{cite news |last=Starr |first=Michelle |title=Bizarre Star Found Hurtling Out of Our Galaxy Centre Is Fastest of Its Kind Ever Seen |url=https://www.sciencealert.com/our-bossy-black-hole-kicked-out-a-star-and-it-s-shooting-through-the-galaxy-insanely-fast |date=31 July 2019 |work=ScienceAlert.com |access-date=18 November 2019 }}</ref><ref name="NA-20191113">{{cite news |last=Irving |first=Michael |title=Fastest star ever found is being flicked out of the Milky Way |url=https://newatlas.com/space/fastest-star-hypervelocity-ejected-milky-way/ |date=13 November 2019 |work=NewAtlas.com |access-date=18 November 2019 }}</ref>

===Deep-sky objects===
[[File:From Cosmic Spare Tyre to Ethereal Blossom.tif|right|thumb|[[IC 5148]], the spare-tyre nebula as imaged by the [[European Southern Observatory|ESO]] Faint Object Spectrograph and Camera (EFOSC2) on the [[New Technology Telescope]] at La Silla]]
Nicknamed the spare-tyre nebula,<ref name="ESO12">{{cite web|url=http://www.eso.org/public/images/potw1242a/|title=From Cosmic Spare Tyre to Ethereal Blossom|last=ESO|date=2012|work=Picture of the Week|publisher=European Southern Observatory|access-date=6 February 2014}}</ref> [[IC 5148]] is a [[planetary nebula]] located around 1 degree west of Lambda Gruis.<ref name="streicher">{{cite web | last = Streicher  | first = Magda  | date = December 2010 | title = Grus—An Elegant Starry Bird  | publisher = The Astronomical Society of Southern Africa  | work = Deepsky Delights  | url =http://www.mnassa.org.za/html/Dec2010/2010MNASSA..69..Dec..229.pdf |pages = 56–59  | access-date = 7 February 2014}}</ref> Around 3000 light-years distant, it is expanding at 50 kilometres a second, one of the fastest rates of expansion of all planetary nebulae.<ref name="ESO12"/>

Northeast of Theta Gruis are four interacting galaxies known as the Grus Quartet.<ref name=Bakich>{{cite book|last=Bakich|first=Michael E.|title=1,001 Celestial Wonders to See Before You Die|url=https://archive.org/details/celestialwonders00baki_814|url-access=limited|date=2010|publisher=Springer Science+Business Media, LLC|location=New York, New York|isbn=978-1-4419-1777-5|page=[https://archive.org/details/celestialwonders00baki_814/page/n342 334]}}</ref> These galaxies are [[NGC 7552]], [[NGC 7590]], [[NGC 7599]], and [[NGC 7582]].<ref name=koribalski>{{cite web|url=http://www.atnf.csiro.au/people/bkoribal/ngc7582/grus_hi.html|title=The Grus-Quartet|author=Koribalski, Bärbel |date=1996|access-date=28 January 2014}}</ref> The latter three galaxies occupy an area of sky only 10 arcminutes across and are sometimes referred to as the "Grus Triplet," although all four are part of a larger loose group of galaxies called the IC 1459 Grus Group.<ref name="O'Meara"/> NGC 7552 and 7582 are exhibiting high [[Starburst galaxy|starburst]] activity; this is thought to have arisen because of the tidal forces from interacting.<ref name=koribalski/> Located on the border of Grus with Piscis Austrinus,<ref name="streicher"/> [[IC 1459]] is a peculiar E3 giant [[elliptical galaxy]]. It has a fast counterrotating stellar core, and shells and ripples in its outer region.<ref>{{cite journal |author1= Verdoes Kleijn, Gijs A. |author2=van der Marel, Roeland P. |author3-link=C. Marcella Carollo |author3=Carollo, C. Marcella |author4=de Zeeuw, P. Tim  |date=2000|title=The Black Hole in IC 1459 from Hubble Space Telescope Observations of the Ionized Gas Disk|journal=The Astronomical Journal|volume=120|issue=3 |pages=1221–37 |arxiv = astro-ph/0003433 |bibcode = 2000AJ....120.1221V |doi = 10.1086/301524 }}</ref><!-- cites previous two sentences --> The galaxy has an apparent magnitude of 11.9<ref>{{cite web |url =http://simbad.u-strasbg.fr/simbad/sim-id?Ident=IC+1459+&NbIdent=1&Radius=2&Radius.unit=arcmin&submit=submit+id |title =IC 1459 – LINER-type Active Galaxy Nucleus |work = SIMBAD Astronomical Database|publisher=Centre de Données astronomiques de Strasbourg |access-date = 7 February 2014}}</ref> and is around 80 million light-years distant.<ref name="streicher"/>

[[NGC 7424]] is a [[barred spiral galaxy]] with an apparent magnitude of 10.4.<ref>{{cite web |url =http://simbad.u-strasbg.fr/simbad/sim-id?Ident=NGC+7424 |title = NGC 7424 – Galaxy in Group of Galaxies |work = SIMBAD Astronomical Database|publisher=Centre de Données astronomiques de Strasbourg |access-date = 4 February 2014}}</ref> located around 4 degrees west of the Grus Triplet.<ref name="streicher"/> Approximately 37.5 million light-years distant, it is about 100,000 light-years in diameter, has well defined spiral arms and is thought to resemble the [[Milky Way]].<ref>{{Cite APOD|title=Grand Spiral Galaxy NGC 7424 |date=8 January 2013|access-date=4 February 2014}}</ref> Two [[ultraluminous X-ray source]]s and one [[supernova]] have been observed in NGC 7424.<ref name="soria06">{{cite journal |author1=Soria, R. |author2=Kuncic, Z. |author3=Broderick, J. W. |author4=Ryder, S. D. | title = Multiband Study of NGC 7424 and its Two Newly-discovered ULXs | journal = Monthly Notices of the Royal Astronomical Society |date=2006 | volume = 370 | issue = 4 | pages = 1666–76 | bibcode = 2006MNRAS.370.1666S | doi = 10.1111/j.1365-2966.2006.10629.x|doi-access=free |arxiv = astro-ph/0606080 |s2cid=17098189 }}</ref> [[SN 2001ig]] was discovered in 2001 and classified as a [[Type IIb supernova#Type IIb supernovae|Type IIb supernova]], one that initially showed a weak hydrogen line in its [[stellar spectrum|spectrum]], but this emission later became undetectable and was replaced by lines of oxygen, magnesium and calcium, as well as other features that resembled the spectrum of a [[Type Ib supernova]].<ref>{{cite journal|author1=Maund, Justyn R. |author2=Wheeler, J. Craig |author3=Patat, Ferdinando |author4=Wang, Lifan |author5=Baade, Dietrich |author6=Höflich, Peter A. |date=2007|title=Spectropolarimetry of the Type IIb Supernova 2001ig*|journal=The Astrophysical Journal|volume=671|issue=2|pages=1944–1958|arxiv = 0709.1487 |bibcode = 2007ApJ...671.1944M |doi = 10.1086/523261 |s2cid=15234633 }}</ref> A massive star of [[spectral type]] F, A or B is thought to be the surviving binary companion to SN 2001ig, which was believed to have been a [[Wolf–Rayet star]].<ref name="ryder06">{{cite journal |author1=Ryder, Stuart D. |author2=Murrowood, Clair E. |author3=Stathakis, Raylee A. | title = A Post-mortem Investigation of the Type IIb Supernova 2001ig| journal = Monthly Notices of the Royal Astronomical Society | date = 2006 | volume = 369
| issue = 1 | pages = L32–L36 | bibcode = 2006MNRAS.369L..32R| doi = 10.1111/j.1745-3933.2006.00168.x|doi-access=free |arxiv = astro-ph/0603336 |s2cid=15543433 }}</ref>

Located near Alnair is [[NGC 7213]],<ref name="streicher"/> a face-on type 1 [[Seyfert galaxy]] located approximately 71.7 million light-years from Earth.<ref name="hameed">{{cite journal|author1=Hameed, Salman |author2=Blank, David L. |author3=Young, Lisa M. |author4=Devereux, Nick |date=2001|title= The Discovery of a Giant Hα Filament in NGC 7213|journal=The Astrophysical Journal|volume=546|issue=2|pages=L97–L100|url=https://cds.cern.ch/record/476765/files/0011208.pdf |archive-url=https://web.archive.org/web/20210224231211/https://cds.cern.ch/record/476765/files/0011208.pdf |archive-date=2021-02-24 |url-status=live|arxiv = astro-ph/0011208 |bibcode = 2001ApJ...546L..97H |doi = 10.1086/318865 |s2cid=2657286 }}</ref> It has an apparent magnitude of 12.1.<ref>{{cite web |url =http://simbad.u-strasbg.fr/simbad/sim-id?Ident=NGC%207213 |title = NGC 7213 – Type 1 Seyfert Galaxy |work = SIMBAD Astronomical Database|publisher=Centre de Données astronomiques de Strasbourg |access-date = 5 February 2014}}</ref> Appearing undisturbed in visible light, it shows signs of having undergone a collision or merger when viewed at longer wavelengths, with disturbed patterns of ionized hydrogen including a filament of gas around 64,000 light-years long.<ref name="hameed"/> It is part of a group of ten galaxies.<ref name=fouque>{{cite journal|last1=Fouque|first1=P.|last2=Proust|first2=D.|last3=Quintana|first3=H.|last4=Ramirez|first4=A.|year=1993|title=Dynamics of the Pavo-Indus and Grus Clouds of Galaxies|journal=Astronomy and Astrophysics Supplement Series|volume=100|issue=3|pages=493–500|bibcode=1993A&AS..100..493F}}</ref>

[[NGC 7410]] is a spiral galaxy discovered by British astronomer [[John Herschel]] during observations at the [[Cape of Good Hope]] in October 1834. The galaxy has a visual magnitude of 11.7 and is approximately 122 million light-years distant from Earth.<ref name="O'Meara">{{cite book|last=O'Meara|first=Stephen James|title=Deep Sky Companions: Southern Gems|date=2013|publisher=Cambridge University Press|location=New York, New York|isbn=978-1-107-01501-2|pages=418–26|url=http://simbad.u-strasbg.fr/simbad/sim-id?Ident=NGC%207213}}</ref>

==See also==
* [[Grus in Chinese astronomy]]
* [[List of star names in Grus]]

==Notes==
{{notelist}}

==References==
{{reflist}}

===Cited text===
* {{citation |title = Stars and Planets Guide |last1 = Ridpath |first1 = Ian |last2 = Tirion |first2 = Wil |year = 2001 |publisher = Princeton University Press |isbn = 0-691-08913-2}}

==External links==
{{Commons and category|Grus (constellation)|Grus (constellation)}}
* [http://www.allthesky.com/constellations/grus/constell.html The Deep Photographic Guide to the Constellations: Grus]
* [http://astrojan.nhely.hu/grus.htm The clickable Grus]
* [http://www.starrynightphotos.com/constellations/grus.htm Starry Night Photography – Grus Constellation]

{{Stars of Grus}}
{{navconstel}}
{{Portal bar|Astronomy|Stars|Outer space}}
{{Sky|22|00|00|-|47|00|00|10}}

{{DEFAULTSORT:Grus (Constellation)}}
[[Category:Grus (constellation)| ]]
[[Category:Southern constellations]]
[[Category:Constellations listed by Petrus Plancius]]