View source for LL Pegasi

{{Short description|Variable star in the constellation Pegasus}}
{{Starbox begin | name = LL Pegasi}}
{{Starbox image
| image = [[Image:Celestial spiral with a twist.jpg|250px]]
| caption = LL Pegasi is continuously losing gaseous material as it evolves into a planetary nebula.<ref name="ALMAImage"/>
}}
{{Starbox observe
| epoch = [[J2000.0]]
| equinox = [[J2000.0]] ([[International Celestial Reference System|ICRS]])
| constell = [[Pegasus (constellation)|Pegasus]]
| ra = {{RA|23|19|12.607}}<ref name=2mass/>
| dec = {{DEC|+17|11|33.13}}<ref name=2mass/>
| appmag_v=
}}
{{Starbox character
| type = [[Asymptotic giant branch]]<ref name=lombaert/>
| class = C<ref name=groenewegen/>
| b-v = 
| r-i =
| variable = [[Mira variable|Mira]]<ref name=gcvs/>
}}
{{Starbox astrometry
| radial_v =
| prop_mo_ra =
| prop_mo_dec =
| parallax =
| p_error =
| parallax_footnote =
| dist_pc = 1,300<ref name=lombaert/>
| absmag_v=
}}
{{Starbox detail
| component1 = A
| mass = 3.5<ref name=Kim2012/>
| radius = {{solar radius calculator|type=LT|10900|1800|decimals=-2}}<ref name=massalkhi>{{Cite journal|last1=Massalkhi|first1=S.|last2=Agúndez|first2=M.|last3=Cernicharo|first3=J.|date=August 2019|title=Study of CS, SiO, and SiS abundances in carbon star envelopes: Assessing their role as gas-phase precursors of dust|arxiv=1906.09461|journal=Astronomy & Astrophysics|volume=628|pages=A62|doi=10.1051/0004-6361/201935069|pmid=31511746 |pmc=6739229 |bibcode=2019A&A...628A..62M |issn=0004-6361}}</ref>{{efn|name=radius}}
| luminosity = 10,900<ref name=massalkhi/>
| temperature = 1,800<ref name=massalkhi/>
| component2 = B
| mass2 = 3.1<ref name=Kim2012/>
}}
{{Starbox catalog
| names = {{odlist|V=LL Pegasi|2MASS=J23191260+1711331|IRAS=23166+1655}}, RAFGL&nbsp;3068
}}
{{Starbox reference
| Simbad=LL+Pegasi
}}
{{Starbox end}}

'''LL Pegasi''' ('''AFGL 3068''') is a [[Mira variable]] star surrounded by a pinwheel-shaped nebula, '''IRAS 23166+1655''', thought to be a [[Protoplanetary nebula|preplanetary nebula]].  It is a [[binary system (astronomy)|binary system]] that includes an extreme [[carbon star]].  The pair is hidden by the [[dust cloud]] ejected from the carbon star and is only visible in [[infrared]] light.<ref name=morris/>

==Variability==
[[File:LLPegLightCurve.png|thumb|left|A near-infrared ([[Photometric_system#Photometric_letters|L- band]]) [[light curve]] for LL Pegasi, plotted from data published by Le Bertre (1992)<ref name=lebertre/>]]
LL Pegasi is obscured at visual wavelengths, but is strongly variable in brightness at [[infrared]] wavelengths.<ref name=lebertre/>  It is classified as a Mira variable and has a period of about 696 days.<ref name=whitelock/>

==Nebula==
The [[nebula]] displays an unusual [[Archimedean spiral]] shape.  The shape is thought to be formed through the interaction between the stellar companion and the carbon star, as has been seen in other [[binary star|binary]] systems, although not with such a precise geometric form.  The distance between the spiral arms and their rate of expansion is consistent with estimates of the pair's 810 year orbital period based on their apparent angular separation.<ref name=morris/>

==Gallery==
<gallery>
3D view of LL Pegasi.webm|Observed structure surrounding the binary star system.
Pre-planetary nebula, IRAS 23166+1655.jpg|[[Hubble Space Telescope]] image of IRAS 23166+1655, taken in the near-infrared. The bright object to the right is a star much closer to Earth. It was used as a [[guide star]] for [[adaptive optics]] corrections that allowed the [[Keck II]] telescope to resolve the LL Pegasi binary pair.
</gallery>

==Notes==
{{notelist|notes=

{{efn | name=radius | Applying the [[Stefan–Boltzmann law]] with a nominal [[sun|solar]] [[effective temperature]] of 5,772&nbsp;[[Kelvin|K]]: 
:<math>\sqrt{\biggl(\frac{5,772}{1,800}\biggr)^4 \cdot {10,900}} = 1,100\ R_\odot</math>.}}

}}
== See also ==

* [[List of largest known stars]]

==References==
{{Reflist|refs=

<ref name="ALMAImage">{{cite web |title=Celestial spiral with a twist |url=https://www.eso.org/public/images/potw1710a/ |website=eso.org |publisher=European Southern Observatory |access-date=13 February 2022}}</ref>

<ref name=2mass>{{cite journal |bibcode=2003yCat.2246....0C |title=VizieR Online Data Catalog: 2MASS All-Sky Catalog of Point Sources (Cutri+ 2003) |journal=CDS/ADC Collection of Electronic Catalogues |pages=II/246 |volume=2246 |last1=Cutri |first1=Roc M. |last2=Skrutskie |first2=Michael F. |last3=Van Dyk |first3=Schuyler D. |last4=Beichman |first4=Charles A. |last5=Carpenter |first5=John M. |last6=Chester |first6=Thomas |last7=Cambresy |first7=Laurent |last8=Evans |first8=Tracey E. |last9=Fowler |first9=John W. |last10=Gizis |first10=John E. |last11=Howard |first11=Elizabeth V. |last12=Huchra |first12=John P. |last13=Jarrett |first13=Thomas H. |last14=Kopan |first14=Eugene L. |last15=Kirkpatrick |first15=J. Davy |last16=Light |first16=Robert M. |last17=Marsh |first17=Kenneth A. |last18=McCallon |first18=Howard L. |last19=Schneider |first19=Stephen E. |last20=Stiening |first20=Rae |last21=Sykes |first21=Matthew J. |last22=Weinberg |first22=Martin D. |last23=Wheaton |first23=William A. |last24=Wheelock |first24=Sherry L. |last25=Zacarias |first25=N. |year=2003 |url=http://vizier.u-strasbg.fr/viz-bin/VizieR?-source=II/246 }}</ref>

<ref name=Kim2012>{{Cite journal |last=Kim |first=Hyosun |last2=Taam |first2=Ronald E. |date=2012-10-17 |title=A NEW METHOD OF DETERMINING THE CHARACTERISTICS OF EVOLVED BINARY SYSTEMS REVEALED IN THE OBSERVED CIRCUMSTELLAR PATTERNS: APPLICATION TO AFGL 3068 |url=http://dx.doi.org/10.1088/2041-8205/759/1/l22 |journal=The Astrophysical Journal |volume=759 |issue=1 |pages=L22 |doi=10.1088/2041-8205/759/1/l22 |issn=2041-8205|arxiv=1209.6360 }}</ref>

<ref name=lombaert>{{cite journal|bibcode=2012A&A...544L..18L|title=Observational evidence for composite grains in an AGB outflow. MgS in the extreme carbon star LL Pegasi|journal=Astronomy & Astrophysics|volume=544|pages=L18|last1=Lombaert|first1=R.|last2=De Vries|first2=B. L.|last3=De Koter|first3=A.|last4=Decin|first4=L.|last5=Min|first5=M.|last6=Smolders|first6=K.|last7=Mutschke|first7=H.|last8=Waters|first8=L. B. F. M.|year=2012|doi=10.1051/0004-6361/201219782|arxiv = 1207.1606 |s2cid=119022145}}</ref>

<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|display-authors=etal|last1=Samus|first1=N. N.|last2=Durlevich|first2=O. V.|year=2009}}</ref>

<ref name=morris>{{cite journal|bibcode=2006IAUS..234..469M|title=A Binary-Induced Pinwheel Outflow from the Extreme Carbon Star, AFGL 3068|journal=Planetary Nebulae in Our Galaxy and Beyond|volume=234|pages=469|last1=Morris|first1=Mark|last2=Sahai|first2=Raghvendra|last3=Matthews|first3=Keith|last4=Cheng|first4=Judy|last5=Lu|first5=Jessica|last6=Claussen|first6=Mark|last7=Sánchez-Contreras|first7=Carmen|year=2006|doi=10.1017/S1743921306003784|doi-access=free}}</ref>

<ref name=whitelock>{{cite journal|bibcode=2006MNRAS.369..751W|arxiv=astro-ph/0603504|title=Near-infrared photometry of carbon stars|journal=Monthly Notices of the Royal Astronomical Society|volume=369|issue=2|pages=751–782|last1=Whitelock|first1=Patricia A.|last2=Feast|first2=Michael W.|last3=Marang|first3=Freddy|last4=Groenewegen|first4=M. A. T.|year=2006|doi=10.1111/j.1365-2966.2006.10322.x|doi-access=free |s2cid=14453496}}</ref>

<ref name=lebertre>{{cite journal|bibcode=1992A&AS...94..377L|title=Carbon-star lightcurves in the 1-20 micron range|journal=Astronomy and Astrophysics Supplement Series|volume=94|pages=377|last1=Le Bertre|first1=T.|year=1992}}</ref>

<ref name=groenewegen>{{cite journal|bibcode=1994A&A...287..163G|title=The 3 micrometer spectra of candidate carbon stars|journal=Astronomy and Astrophysics|volume=287|pages=163|last1=Groenewegen|first1=M. A. T.|last2=De Jong|first2=T.|last3=Gaballe|first3=T. R.|year=1994}}</ref>

}}

==External links==
*[https://www.eso.org/public/videos/potw1710a/ 3D view of LL Pegasi]
*[https://www.eso.org/public/images/potw1710a/ Celestial spiral with a twist]
*[http://www.spacetelescope.org/images/potw1020a/ An Extraordinary Celestial Spiral]
*[https://web.archive.org/web/20100909151403/http://cosmiclog.msnbc.msn.com/_news/2010/09/07/5062638-celestial-spiral-goes-viral Celestial spiral goes viral]
*[http://news.discovery.com/space/hubble-spots-ghostly-space-spiral.html Hubble Spots Ghostly Space Spiral — discovery.com]
*[http://antwrp.gsfc.nasa.gov/apod/ap100914.html An Extraordinary Spiral from LL Pegasi], APOD

{{Stars of Pegasus}}

{{DEFAULTSORT:LL Pegasi}}
[[Category:Protoplanetary nebulae]]
[[Category:IRAS catalogue objects]]
[[Category:Objects with variable star designations|Pegasi, LL]]
[[Category:Pegasus (constellation)]]
[[Category:Carbon stars]]
[[Category:Mira variables]]
[[Category:2MASS objects|J23191260+1711331]]
[[Category:TIC objects]]