View source for Pi1 Gruis

{{Short description|Semiregular variable star in the constellation Grus}}
{{DISPLAYTITLE:Pi<sup>1</sup> Gruis}}
{{other stars by Bayer designation|Pi Gruis{{!}}π Gruis}}
{{Starbox begin | name=π<sup>1</sup> Gruis }}
{{Starbox image
| image=
{{Location mark
|image=The surface of the red giant star π1 Gruis from PIONIER on the VLT.jpg|alt=|float=center|width=260
}}
|caption=Surface of the red giant star π1 Gruis.<ref name=ESO>{{cite web|title=Giant Bubbles on Red Giant Star's Surface|url=https://www.eso.org/public/news/eso1741/|website=www.eso.org|accessdate=21 December 2017}}</ref>
}}
{{Starbox observe |
epoch=J2000 |
ra={{RA|22|22|44.20571}}<ref name=hipparcos/>|
dec={{DEC|−45|56|52.6115}}<ref name=hipparcos/> |
appmag_v=5.31 - 7.01<ref name=asa>{{cite journal|bibcode=2002AcA....52..397P|title=The All Sky Automated Survey. Catalog of Variable Stars. I. 0 h - 6 h ''Quarter'' of the Southern Hemisphere|journal=Acta Astronomica|volume=52|pages=397–427|last1=Pojmanski|first1=G.|year=2002|arxiv = astro-ph/0210283 }}</ref> + 10.4<ref name=mayer/>|
constell=[[Grus (constellation)|Grus]] }}
{{Starbox character |
class=S5,7:<ref name=stewart>{{cite journal|bibcode=2015ApJS..221...30S|arxiv=1511.01670|title=An Atlas of Bright Star Spectra in the Near-infrared from Cassini-VIMS|journal=The Astrophysical Journal Supplement Series|volume=221|issue=2|pages=30|last1=Stewart|first1=Paul N.|last2=Tuthill|first2=Peter G.|last3=Nicholson|first3=Philip D.|last4=Sloan|first4=G. C.|last5=Hedman|first5=Matthew M.|year=2015|doi=10.1088/0067-0049/221/2/30|s2cid=118435831}}</ref> + G0V<ref name=mayer/>
|variable=[[semi-regular variable|SRb]]<ref name=gcvs>{{cite journal|bibcode=2009yCat....102025S|title=VizieR Online Data Catalog: General Catalogue of Variable Stars (Samus+ 2007-2013)|journal=VizieR On-line Data Catalog: B/GCVS. Originally Published in: 2009yCat....102025S|volume=1|pages=B/gcvs|display-authors=etal|last1=Samus|first1=N. N.|last2=Durlevich|first2=O. V.|year=2009}}</ref>
}}
{{Starbox astrometry
| parallax=6.13
| p_error=0.76
| parallax_footnote=<ref name=hipparcos>{{cite journal|bibcode=2007A&A...474..653V|title=Validation of the new Hipparcos reduction|journal=Astronomy and Astrophysics|volume=474|issue=2|pages=653–664|last1=Van Leeuwen|first1=F.|year=2007|doi=10.1051/0004-6361:20078357|arxiv = 0708.1752 |s2cid=18759600}}</ref>
| absmag_v=G0: +4.3<ref name=mayer/>
}}
{{Starbox orbit
| reference = <ref name=mayer/>
| period_unitless = 6,200 years
| axis = 2.8
| axis_unitless = 460 AU
}}
{{Starbox detail
| component1 = A
| mass = 1.5<ref name=mayer>{{cite journal|bibcode=2014A&A...570A.113M|arxiv=1408.3965|title=Large-scale environments of binary AGB stars probed by Herschel. II. Two companions interacting with the wind of π1 Gruis|journal=Astronomy & Astrophysics|volume=570|issue=113|pages=A113|last1=Mayer|first1=A.|last2=Jorissen|first2=A.|last3=Paladini|first3=C.|last4=Kerschbaum|first4=F.|last5=Pourbaix|first5=D.|last6=Siopis|first6=C.|last7=Ottensamer|first7=R.|last8=Mečina|first8=M.|last9=Cox|first9=N. L. J.|last10=Groenewegen|first10=M. A. T.|last11=Klotz|first11=D.|last12=Sadowski|first12=G.|last13=Spang|first13=A.|last14=Cruzalèbes|first14=P.|last15=Waelkens|first15=C.|year=2014|doi=10.1051/0004-6361/201424465|s2cid=119282752}}</ref>
| temperature = 2,300<ref name="wallstrom"/>{{snd}}3,100<ref name=mayer/>
| radius = {{solar radius calculator|type=AD|21|0.164}}<ref name="wallstrom">{{Cite journal |last1=Wallstrom |first1=S. H. J. |last2=Danilovich |first2=T. |last3=Muller |first3=H. S. P. |last4=Gottlieb |first4=C. A. |last5=Maes |first5=S. |last6=Van de Sande |first6=M. |last7=Decin |first7=L. |last8=Richards |first8=A. M. S. |last9=Baudry |first9=A. |last10=Bolte |first10=J. |last11=Ceulemans |first11=T. |last12=De Ceuster |first12=F. |last13=de Koter |first13=A. |last14=Mellah |first14=I. El |last15=Esseldeurs |first15=M. |date=December 6, 2023 |title=ATOMIUM: Molecular inventory of 17 oxygen-rich evolved stars observed with ALMA |journal=Astronomy & Astrophysics |volume=681 |pages=A50 |doi=10.1051/0004-6361/202347632 |issn=0004-6361|arxiv=2312.03467 }}</ref>{{efn|Calculated using angular diameter and distance in Table 1}}
| luminosity = 7,244<ref name=mayer/>
| component2 = B
| mass2 = 1.0<ref name=mayer/>
| temperature2 =
| radius2 =
| luminosity2 =
}}
{{Starbox catalog
| names = [[Cordoba Durchmusterung|CD]]−46°14292, [[Harvard Revised catalogue|HR]]&nbsp;8521, [[Henry Draper catalogue|HD]]&nbsp;212087, [[Smithsonian Astrophysical Observatory Star Catalog|SAO]]&nbsp;231105, [[Hipparcos#Published catalogues|HIP]]&nbsp;110478
}}
{{Starbox reference
| Simbad = pi01+Gru
}}
{{Starbox end}}
'''π<sup>1</sup> Gruis''' ('''Pi<sup>1</sup> Gruis''')  is a [[semiregular variable star]] in the [[constellation]] [[Grus (constellation)|Grus]] around 530 [[light-year]]s from Earth.  It forms a close naked-eye double with [[Pi2 Gruis|π<sup>2</sup> Gru]] four arc-minutes away.
[[File:Pi1GruLightCurve.png|thumb|left|A [[Photometric_system#Photometric_letters|visual band]] [[light curve]] for π<sup>1</sup> Gruis, adapted from Mayer ''et al.'' (2014)<ref name=mayer/>]]
π<sup>1</sup> Gruis is an [[asymptotic giant branch]] (AGB) star of spectral type S5. It is one of the brightest members of a class of stars known as [[S-type star|S stars]]. It is also a semi-regular variable star ranging from [[apparent magnitude]] 5.3 to 7.0 over a period of 198.8 days.<ref name=tabur>{{cite journal|bibcode=2009MNRAS.400.1945T|arxiv=0908.3228|title=Long-term photometry and periods for 261 nearby pulsating M giants|journal=Monthly Notices of the Royal Astronomical Society|volume=400|issue=4|pages=1945|last1=Tabur|first1=V.|last2=Bedding|first2=T. R.|last3=Kiss|first3=L. L.|last4=Moon|first4=T. T.|last5=Szeidl|first5=B.|last6=Kjeldsen|first6=H.|year=2009|doi=10.1111/j.1365-2966.2009.15588.x|doi-access=free |s2cid=15358380}}</ref> It is an ageing star, thought to be well on its way transitioning from a red giant to a [[planetary nebula]]. A shell of material has been detected at a distance of 0.91 [[light-year]]s (0.28 [[parsec]]s), which is estimated to have been ejected 21,000 years ago.<ref>{{cite journal|title=Circumstellar shells resolved in IRAS survey data. II - Analysis|last1=Young |first1=K. |last2=Phillips|first2=T. G. |last3=Knapp|first3=G. R.|journal=Astrophysical Journal|volume=409|pages=725–38 |bibcode=1993ApJ...409..725Y|date=1993|doi=10.1086/172702 }}</ref> Closer to the star, there appears to be a cavity within {{val|200|ul=AU}}, suggesting a drop off in the ejection of material in the past 90 years. The presence of one companion makes the shape of the shell irregular (rather than spherical), and there may as yet be another undetected companion contributing to this.<ref name=sacuto>{{cite journal|author=Sacuto, S.|display-authors=4|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|doi-access=free}}</ref>
π<sup>1</sup> Gruis has a companion star of apparent magnitude 10.9 that is sunlike in properties—a yellow [[main sequence]] star of spectral type G0V. Separated by {{val|2.71||ul="}}, the pair make up a likely binary system. The primary star has a measured diameter of 18.37 milliarcseconds,<ref name=nature>{{cite journal|doi=10.1038/nature25001|pmid=29258298|title=Large granulation cells on the surface of the giant star π1 Gruis|journal=Nature|volume=553|issue=7688|pages=310–312|year=2017|last1=Paladini|first1=C|last2=Baron|first2=F|last3=Jorissen|first3=A|last4=Le Bouquin|first4=J.-B|last5=Freytag|first5=B|last6=Van Eck|first6=S|last7=Wittkowski|first7=M|last8=Hron|first8=J|last9=Chiavassa|first9=A|last10=Berger|first10=J.-P|last11=Siopis|first11=C|last12=Mayer|first12=A|last13=Sadowski|first13=G|last14=Kravchenko|first14=K|last15=Shetye|first15=S|last16=Kerschbaum|first16=F|last17=Kluska|first17=J|last18=Ramstedt|first18=S|s2cid=4466336}}</ref> corresponding to a size 350 times that of the Sun.<ref name=ESO/>
The star was catalogued by French explorer and astronomer [[Nicolas Louis de Lacaille]] in 1756 but not given a name. Instead, he gave the [[Bayer designation]] of "π Gruis" to π<sup>2</sup>. It was [[Thomas Brisbane]] who designated this star as π<sup>1</sup>.<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|VA]]  | isbn = 978-0-939923-78-6 |pages=360–62}}</ref> [[Annie Jump Cannon]] was the first to report its unusual [[stellar spectrum|spectrum]], sending a plate of its spectrograph made in 1895 to [[Paul W. Merrill]] and noting its similarity to [[R Andromedae]]. Merrill selected these two stars along with [[R Cygni]] to be the three prototypes of the S star class.<ref>{{cite journal|last=Merrill|first=Paul W.|date=1955|title=Red Stars|journal=Publ. Astron. Soc. Pac.|volume=67|issue=397|pages=199–213|bibcode=1955PASP...67..199M|doi=10.1086/126804|s2cid=239491440 }}</ref> π<sup>1</sup> Gruis was one of the first 17 stars defined as S-stars by Merrill in 1922; the only star not observed from Mount Wilson due to its southerly location in the sky.<ref name="merrill22">{{cite journal|last=Merrill|first=Paul W.|date=1922|title=Stellar spectra of class S|journal=Astrophysical Journal|volume=56|pages=457–82|bibcode=1922ApJ....56..457M|doi=10.1086/142716}}</ref> Analysis of its spectrum showed bands indicating the presence of [[technetium]],<ref>{{cite journal |last1=Little|first1=Stephen J. |last2=Little-Marenin|first2=Irene R. |last3=Bauer|first3=Wendy Hagen |date=1987 |title=Additional late-type stars with technetium |journal=Astronomical Journal |volume=94 |pages=981–995 |bibcode=1987AJ.....94..981L |doi=10.1086/114532|doi-access=free }}</ref> as well as oxides of [[zirconium]], [[lanthanum]], [[cerium]] and [[yttrium]] but not [[titanium]] nor [[barium]] which have been recorded in other S stars.<ref>{{cite journal|last=Murty|first=P.S.|date=1983|title=Pi Gruis - Molecular identifications and spectral classification|journal=Astrophysics and Space Science|volume=94|issue=2|pages=295–305|issn=0004-640X|bibcode=1983Ap&SS..94..295M|doi=10.1007/BF00653719|s2cid=122165729}}</ref>
==Notes==
{{Notelist}}
==References==
{{reflist}}
{{Stars of Grus}}
{{DEFAULTSORT:Pi1 Gruis}}
[[Category:Grus (constellation)]]
[[Category:Bayer objects|Gruis, Pi1]]
[[Category:S-type stars]]
[[Category:G-type main-sequence stars]]
[[Category:Hipparcos objects|110478]]
[[Category:Bright Star Catalogue objects|8521]]
[[Category:Henry Draper Catalogue objects|212087]]
[[Category:Durchmusterung objects]]
[[Category:Semiregular variable stars]]
[[Category:Asymptotic-giant-branch stars]]
[[Category:Binary stars]]