View source for Sakurai's Object

{{Short description|Star in the constellation Sagittarius}}
{{Use dmy dates|date=July 2019}}
{{Good article}}
{{Starbox begin
| name=Sakurai's Object
}}
{{Starbox image
| image=[[File:Sakurai's Object cropped.jpg|280px]]
| caption=Sakurai's Object (photo by [[ESO]])
}}
{{Starbox observe
| epoch=[[J2000.0]] ([[International Celestial Reference System|ICRS]])
| constell = [[Sagittarius (constellation)|Sagittarius]]
| ra = {{RA|17|52|32.69}}<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>
| dec = {{DEC|−17|41|08.0}}<ref name=2mass/>
| appmag_v = {{nowrap|10.90 - 21<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>}}
}}
{{Starbox character
| appmag_2_passband = [[J band (infrared)|J]]
| appmag_2 = {{nowrap|11.555 ± 0.022<ref name=2mass/>}}
| class=variable
| b-v=+0.81<ref name=ALetters>{{cite journal|bibcode=1997AstL...23..623A|title=UBV photometry of Sakurai's object in 1996 and remarks about its evolutionary status|journal=Astronomy Letters|volume=23|pages=623|last1=Arkhipova|first1=V. P.|last2=Noskova|first2=R. I.|year=1997|issue=5}}</ref>
| u-b=+0.27<ref name=ALetters/>
| v-r=+0.57<ref name=ALetters/>
}}
{{Starbox astrometry
| dist_pc = 1800-5000<ref name = "photoionization">{{cite journal| last1= van Hoof|first1= P. A. M.|last2= Hajduk |first2= M. |date= 2007|title = The onset of photoionization in Sakurai's Object (V4334 Sagittarii)| journal = Astronomy & Astrophysics| volume= 471|issue= 1| pages = L9–L12| doi= 10.1051/0004-6361:20077932|arxiv = 0706.3857 |bibcode = 2007A&A...471L...9V |s2cid= 119324745}}</ref>
| radial_v={{nowrap|−170 ± 30<ref name=MNRAS>{{cite journal|last1=Eyres|first1=S. P. S.|last2=Geballe|first2=T. R.|last3=Tyne|first3=V. H.|last4=Evans|first4=A.|last5=Smalley|first5=B.|last6=Worters|first6=H. L.|title=Warm high-velocity CO in the wind of Sakurai's Object (= V4334 Sgr)|journal=Monthly Notices of the Royal Astronomical Society|date=May 2004|volume=350|issue=1|pages=L9–L12|doi=10.1111/j.1365-2966.2004.07808.x|doi-access=free |arxiv = astro-ph/0403439 |bibcode = 2004MNRAS.350L...9E |s2cid=18500269}}</ref>}}
| prop_mo_ra=
| prop_mo_dec=
| parallax=
| p_error=
| parallax_footnote=
}}
{{Starbox detail
| mass= 0.6<ref name= "mass">{{cite journal |title= Convective-reactive proton-12C combustion in Sakurai's Object (V4334 Sagittarii) and implications for the evolution and yields from the first generations of stars |date= 2011 |journal= The Astrophysical Journal |page= 89 |volume= 727 |issue= 2 |first1= Falk |last1= Herwig |doi= 10.1088/0004-637X/727/2/89|arxiv = 1002.2241 |bibcode = 2011ApJ...727...89H |s2cid= 51428014 }}</ref>
| luminosity = ~10,000<ref name=hajduk/>
}}
{{Starbox catalog
| names= [[Variable star designation|V4334]]&nbsp;Sgr, V4334&nbsp;Sagittarii, [[2MASS]]&nbsp;J17523269-1741080, DPV&nbsp;1, Sakurai's&nbsp;variable, [[Planetary nebula|PN]]&nbsp;G010.4+04.4, [[Guide Star Catalog|GSC2]]&nbsp;S2202011182877, Sakurai's&nbsp;Object, [[American Association of Variable Star Observers|AAVSO]]&nbsp;1746-17
}}
{{Starbox reference
| Simbad=NAME+SAKURAI'S+OBJECT
}}
{{Starbox end}}
{{Sky|17|52|32.69|-|17|41|08.0|13}}
'''Sakurai's Object''' ('''V4334 Sagittarii''') is a [[star]] in the [[constellation]] of [[Sagittarius (constellation)|Sagittarius]]. It is thought to have previously been a [[white dwarf]] that, as a result of a [[very late thermal pulse]], swelled and became a [[red giant]]. It is located at the center of a [[planetary nebula]] and is believed to currently be in thermal instability and within its final [[shell helium flash]] phase.

At the time of its discovery, astronomers believed Sakurai's Object to be a [[Nova|slow nova]]. Later spectroscopic analysis suggested that the star was not a nova, but had instead undergone a very late thermal pulse similar to that of [[V605 Aquilae]], causing it to vastly expand. V605 Aquilae, which was discovered in 1919, is the only other star known to have been observed during the high luminosity phase of a very late thermal pulse, and models predict that Sakurai's Object, over the next few decades, will follow a similar life cycle.

Sakurai's Object and other similar stars are expected to end up as [[helium]]-rich white dwarfs after retracing their evolution track from the "born-again" giant phase back to the white dwarf cooling track. There are few other suspected "born-again" objects, one example being [[FG Sagittae]]. Having erupted in 1995, it is expected that Sakurai's Object's final helium flash will be the first well-observed one.<ref name="The Astrophysical Journal">{{cite journal|last1=Duerbeck|first1=Hilmar W.|last2=Benetti|first2=Stefano|title=Sakurai's Object—A Possible Final Helium Flash in a Planetary Nebula Nucleus|journal=The Astrophysical Journal|date=10 September 1996|volume=468|issue=2|pages=L111–L114|doi=10.1086/310241|bibcode = 1996ApJ...468L.111D |s2cid=121491943 }}</ref>

==Observation history==
[[File:V4334SgrLightCurve.png|thumb|left|A [[Photometric_system#Photometric_letters|visual band]] [[light curve]] for V4334 Sagittarii, adapted from Duerbeck (2002)<ref name="DuerbeckPhotom"/>]]
An [[IAU Circular|International Astronomical Union Circular]] sent on 23 February 1996 announced the discovery of a "possible 'slow' [[nova]]" of [[Magnitude (astronomy)|magnitude]] 11.4 by Yukio Sakurai, an amateur astronomer.<ref name="ing"/> Japanese astronomer [[Syuichi Nakano]] reported the discovery, drawing attention to the fact that the object had not been visible in images from 1993 nor in [[Harvard-Smithsonian Center for Astrophysics|Center for Astrophysics {{!}} Harvard & Smithsonian]] records for the years 1930–1951, despite it appearing to slowly brighten over the previous years. Nakano wrote that "While the outburst [suggests] a slow or symbiotic nova, the lack of obvious emission lines one year after brightening is very unusual."<ref name ="circular">{{cite journal|bibcode=1996IAUC.6322....1N|title=Novalike Variable in Sagittarius|journal=IAU Circ|volume=6322|pages=1|last1=Nakano|first1=S.|last2=Sakurai|first2=Y.|last3=Hazen|first3=M.|last4=McNaught|first4=R. H.|last5=Benetti|first5=S.|last6=Duerbeck|first6=H. W.|last7=Cappellaro|first7=E.|last8=Leibundgut|first8=B.|year=1996}}</ref>

Following the initial announcement, [[Hilmar Duerbeck]] published a study investigating the "possible final [[helium flash]]" seen by Sakurai. In it, they noted that the location of Sakurai's Object corresponded to a faint object detected in 1976 of magnitude 21, and discussed other observations in the years 1994–1996, by which time the magnitude had increased to around 11–15.<ref name ="Duerbeck1">{{cite journal|title= Sakurai's Object - A possible Final Helium Flash in a Planetary Nebula Nucleus|first1 = Hilmar|last1= Duerbeck|first2= Stefano|last2= Benetti|journal= The Astrophysical Journal|volume= 468|issue = 2|page= L111–L114|date= 10 September 1996|bibcode = 1996ApJ...468L.111D |doi = 10.1086/310241 | s2cid=121491943 }}</ref> By investigating the measured fluxes, angular diameter, and mass of the [[nebula]], a distance of 5.5 k[[parsec|pc]] and [[luminosity]] of {{Solar luminosity|link=y|38}} was determined. The researchers noted that this was in agreement with their appearance and model predictions<ref>{{cite journal|title= On the Evolution of Those Nuclei of Planetary-Nebulae That Experience a Final Helium Shell Flash|first1= I.|last1= Iben|journal= Astrophysical Journal|volume= 264|pages= 605–612|date= 1983|bibcode = 1983ApJ...264..605I |doi = 10.1086/160631 }}</ref> and that the outburst luminosity was in the area of 3100 solar luminosities; lower than predicted by a factor of 3.

The first [[infrared]] observations were published in 1998, in which both [[Near-infrared spectroscopy|near]] and [[Far-infrared astronomy|far]] infrared [[spectroscopy]] data was presented. The collected data showed Sakurai's Object's steep brightening in 1996, followed by a sharp decline in 1999 as expected. It was later found that the star's steep decline in light was due to the [[circumstellar dust]] located around the star, which was present at a temperature of ~680 [[Kelvin|K]].<ref>{{cite journal |title= Infrared Spectroscopy of Sakurai's Object |author= S. Eyres |journal= [[Monthly Notices of the Royal Astronomical Society]] |volume= 298 |issue= 2 |pages= L37–L41 |date= 1998|bibcode = 1998MNRAS.298L..37E |doi = 10.1046/j.1365-8711.1998.01898.x |doi-access= free }}</ref><ref name=PN>{{cite book|editor-last1=Barlow|editor-first1=Michael J.|editor-last2=Méndez|editor-first2=Roberto H.|title=Planetary nebulae in our galaxy and beyond : proceedings of the 234th symposium of the International Astronomical Union held in Waikoloa Beach, Hawaii, USA April 3-7, 2006|date=2006|publisher=Cambridge Univ. Press|location=Cambridge [u.a.]|isbn=978-0-521-86343-8|pages=379–380|url=https://books.google.com/books?id=3dpaBzRbanMC&pg=PA379}}</ref> Further infrared data recorded by the [[United Kingdom Infrared Telescope]] was published in 2000, in which findings of the changing [[Spectral line|absorption lines]] were discussed.<ref name="IR review">{{cite journal |title= The Infrared Evolution of Sakurai's Object |first1= T. R. |last1= Geballe |first2= S. |last2= Eyres |date= 2002 |journal= Astrophysics and Space Science |volume= 279 |pages= 39–49|arxiv = astro-ph/0102043 |bibcode = 2002Ap&SS.279...39G |doi=10.1023/a:1014683521291 |s2cid= 17926499 }}</ref><ref>{{cite journal |title= The continuing saga of Sakurai's object (V4334 Sgr): dust production and helium line emission |date= 2000 |journal= Monthly Notices of the Royal Astronomical Society |pages= 595–599 |volume= 315 |issue= 3 |first1= V. |last1= Tyne |first2= S. |last2= Eyres|bibcode = 2000MNRAS.315..595T |doi = 10.1046/j.1365-8711.2000.03412.x |doi-access= free |hdl= 1885/40061 |hdl-access= free }}</ref>

Observations from the [[United Kingdom Infrared Telescope]] (UKIRT) in 1999 revealed that the star is in a ''RCB-like'' phase with the release of dust and huge loss of mass.<ref name="MNOTRAS">{{cite journal|bibcode=2000MNRAS.315..595T|title=The continuing saga of Sakurai's object (V4334 Sgr): Dust production and helium line emission|journal=Monthly Notices of the Royal Astronomical Society|volume=315|issue=3|pages=595|last1=Tyne|first1=V. H.|last2=Eyres|first2=S. P. S.|last3=Geballe|first3=T. R.|last4=Evans|first4=A.|last5=Smalley|first5=B.|last6=Duerbeck|first6=H. W.|last7=Asplund|first7=M.|year=2000|doi=10.1046/j.1365-8711.2000.03412.x|doi-access=free|hdl=1885/40061|hdl-access=free}}</ref>

Since 2005, it has been observed in the ejected particles of Sakurai's Object that [[photoionization]] of carbon is taking place.<ref name="photoionization"/>

==Properties==
Sakurai's Object is a highly evolved post-[[asymptotic giant branch]] star which has, following a brief period on the [[white dwarf]] cooling track, undergone a [[helium]] shell flash (also known as a very late thermal pulse).<ref name="ing">{{cite journal|bibcode=2000INGN....2....9P|title=The Sakurai Object: A Case Study in Advanced Stellar Evolution|journal=The Newsletter of the Isaac Newton Group of Telescopes (ING Newsl.)|volume=2|pages=9|last1=Pollacco|first1=P.|year=2000}}</ref><ref>{{cite journal |title= Sakurai's Object: characterizing the near-infrared CO ejecta between 2003 and 2007 |date= 2009 |journal= Monthly Notices of the Royal Astronomical Society |volume= 393 |pages= 108–112 |first1= H. |last1= Worters |first2= M. |last2= Rushton |issue= 1 |doi= 10.1111/j.1365-2966.2008.14135.x|doi-access= free |bibcode = 2009MNRAS.393..108W |arxiv= 0810.4556 |s2cid= 16318447 }}</ref><ref name="MNRAS1">{{cite journal|last1=Worters|first1=H. L.|last2=Rushton|first2=M. T.|last3=Eyres|first3=S. P. S.|last4=Geballe|first4=T. R.|last5=Evans|first5=A.|title=Sakurai's Object: characterizing the near-infrared CO ejecta between 2003 and 2007|journal=Monthly Notices of the Royal Astronomical Society|date=11 February 2009|volume=393|issue=1|pages=108–112|doi=10.1111/j.1365-2966.2008.14135.x|doi-access=free |bibcode = 2009MNRAS.393..108W |arxiv=0810.4556|s2cid=16318447}}</ref> The star is thought to have a mass of around {{Solar mass|link=y|0.6}}.<ref name= "mass"/> Observations of Sakurai's Object show increasing reddening and pulsing activity, suggesting that the star is exhibiting thermal instability during its final helium-shell flash.<ref name=ALetters/><ref name="2003ApJ583-913">{{cite journal |first1= T.M. |last1= Lawlor |first2= J. |last2= MacDonald |title= Sakurai's Object, V605 Aquilae, and FG Sagittae: An Evolutionary Sequence Revealed |journal= The Astrophysical Journal |volume= 583 |issue= 2 |pages= 913–922 |date= February 2003 |doi= 10.1086/345411|bibcode = 2003ApJ...583..913L |doi-access= free }}</ref>

Prior to its reignition V4334 Sgr is thought to have been cooling towards a white dwarf with a temperature around 100,000 K and a luminosity around {{solar luminosity|100}}.  The luminosity rapidly increased about a hundred-fold and then the temperature decreased to around 10,000 K.  The star developed the appearance of an F class supergiant (F2 Ia).<ref name="hajduk">{{cite journal|last1=Hajduk|first1=M.|title=The Real-Time Stellar Evolution of Sakurai's Object|journal=Science|date=8 April 2005|volume=308|issue=5719|pages=231–233|doi=10.1126/science.1108953|bibcode = 2005Sci...308..231H|pmid=15821085|s2cid=45275698}}</ref>  The apparent temperature continued to cool to below 6,000 K and the star was gradually obscured at optical wavelengths by the formation of carbon dust, similar to an [[R CrB star]].<ref name=pavlenko/>  Since then the temperature has increased to around 20,000 K.<ref name=hajduk/>

The properties of Sakurai's Object are quite similar to that of [[V605 Aquilae]].<ref name="photoionization">{{cite journal| last1= van Hoof|first1= P. A. M.|last2= Hajduk |first2= M. |date= 2007|title = The onset of photoionization in Sakurai's Object (V4334 Sagittarii)| journal = Astronomy & Astrophysics| volume= 471|issue= 1| pages = L9–L12| doi= 10.1051/0004-6361:20077932|arxiv = 0706.3857 |bibcode = 2007A&A...471L...9V |s2cid= 119324745}}</ref> V605, discovered in 1919, is the only other known star observed during the high luminosity phase of a very late thermal pulse, and Sakurai's Object is modeled to increase in temperature in the next few decades to match the current state of V605.<ref name="2003ApJ583-913" />

===Dust cloud===
{{See also|Cosmic dust}}
During the second half of 1998 an optically thick [[Cosmic dust|dust]] shell obscured Sakurai's Object, causing a rapid decrease in visibility of the star, until in 1999 it disappeared from [[Visible spectrum|optical wavelength]] observations altogether.<ref name=pavlenko>{{cite journal |first1= Y.V. |last1= Pavlenko |first2= T.R. |last2= Geballe |title= Models of infrared spectra of Sakurai's Object (V4334 Sgr) in 1997 |journal= Astronomy & Astrophysics |volume= 390 |issue= 2 |pages= 621–626 |date= 2002|arxiv = astro-ph/0205528 |bibcode = 2002A&A...390..621P |doi = 10.1051/0004-6361:20020732 |s2cid= 51163489 }}</ref> [[Infrared]] observations showed that the dust cloud around the star is primarily [[carbon]] in an [[amorphous]] form.<ref>{{cite journal |title= Modelling the dust cloud around Sakurai's Object |first1= V |last1= Tyne |volume= 279 |pages= 139–147 |date= 2002 |journal= Astrophysics and Space Science|bibcode = 2002Ap&SS.279..139T |doi=10.1023/A:1014672712630|s2cid= 115526277 }}</ref> In 2009 it was discovered that the dust shell is strongly [[asymmetrical]], as a disc with a [[major axis]] oriented at an angle of 134°, and [[Orbital inclination|inclination]] of around 75°. The disc is thought to be growing more [[Opacity (optics)|opaque]] due to the fast spectral evolution of the source towards lower temperatures.<ref>{{cite journal |title= Sakurai's Object (V4334 Sgr): evolution of the dust shell from 1999 to 2001 |journal= Monthly Notices of the Royal Astronomical Society |volume= 334 |issue= 4 |pages= 875–882 |date= 2002 |first1= V |last1= Tyne|bibcode = 2002MNRAS.334..875T |doi = 10.1046/j.1365-8711.2002.05561.x |doi-access= free }}</ref><ref>{{cite journal |title= A dense disk of dust around the born-again Sakurai's object |date= 2009 |journal= Astronomy & Astrophysics |pages= L17–L20 |first1= O. |last1= Chesneau |first2= G. |last2= Clayton |doi= 10.1051/0004-6361:200811173 |volume= 493|issue= 2 |arxiv = 0811.3295 |bibcode = 2009A&A...493L..17C |s2cid= 13370862 }}</ref>

===Planetary nebula===
[[File:Phot-21-96.gif|thumb|upright=1.0|left|Sakurai's Object, by Hilmar Duerbeck, [[ESO]]]]
Sakurai's Object is surrounded by a [[planetary nebula]] created following the star's [[red giant]] phase around 8300 years ago.<ref>{{cite journal |title= Studying the old planetary nebula of V4334 Sgr |date=  2008 |volume= 391 |journal= ASP Conference Series |pages= 163–164 |first1= M. |last1= Hajduk|bibcode= 2008ASPC..391..163H }}</ref> It has been determined that the nebula has a diameter of 44 [[Minute of arc|arcseconds]] and expansion velocity of roughly 32&nbsp;km/s.<ref>{{cite journal |title= Modelling the Planetary Nebula |date= 2002 |volume= 279 |pages= 129–137 |journal= Astrophysics and Space Science |first1= Don |last1= Pollacco|bibcode = 2002Ap&SS.279..129P |doi=10.1023/a:1014620711722|s2cid= 117831251 }}</ref>

===Similarities to other stars===
Research in 1996 revealed that Sakurai's Object possessed the characteristics of a [[R Coronae Borealis variable]] star with the anomaly of [[Carbon-13]] (<sup>13</sup>C) deficit. Also, the [[metallicity]] of Sakurai's object in 1996 was similar to that of V605 Aquilae in 1921. However, it is expected that Sakurai's object will grow in its metallicity to match that of V605 Aquilae.<ref name=PN/>

==Significance in astronomical research==
A significant amount of new star formation and star destruction data is expected to be recorded from continued observation of Sakurai's Object, as well as be used as reference data in the future research of similar stars.<ref name=ing/> For example, Sakurai's Object is a prime target to study the recombination that occurs after planetary nebulae are ionized, because the conditions would be very difficult to replicate in a laboratory.<ref>{{cite journal |doi=10.3847/1538-4357/ac90c4 |title=Recombination of Hot Ionized Nebulae: The Old Planetary Nebula around V4334 SGR (Sakurai's Star) |year=2022 |last1=Reichel |first1=Martin |last2=Kimeswenger |first2=Stefan |last3=Van Hoof |first3=Peter A. M. |last4=Zijlstra |first4=Albert A. |last5=Barría |first5=Daniela |last6=Hajduk |first6=Marcin |last7=Van De Steene |first7=Griet C. |last8=Tafoya |first8=Daniel |journal=The Astrophysical Journal |volume=939 |issue=2 |page=103 |arxiv=2209.03634 |bibcode=2022ApJ...939..103R |s2cid=252118792 |doi-access=free }}</ref> The reason that stars such as Sakurai's Object and V605 Aquilae exist, as well as experience a shorter lifespan compared to most stars, is largely unknown. Sakurai's Object and V605 Aquilae have been observed experiencing born-again behavior for only 10 years, while FG Sagittae has undergone such behavior for 120 years. It is hypothesized that this is due to Sakurai's Object and V605 Aquilae evolving to the [[asymptotic giant branch]] of stars for the first time, while FG Sagittae is undergoing the process a second time.<ref>{{cite journal|bibcode=2003ApJ...583..913L|title=Sakurai's Object, V605 Aquilae, and FG Sagittae: An Evolutionary Sequence Revealed|journal=The Astrophysical Journal|volume=583|issue=2|pages=913|last1=Lawlor|first1=T. M.|last2=MacDonald|first2=J.|year=2003|doi=10.1086/345411|doi-access=free}}</ref>

==References==
{{reflist|refs=

<ref name="DuerbeckPhotom">{{cite journal |last1=DuerbeckPhotom |first1=Hilmar W. |title=Optical photometry of V4334 Sgr (Sakurai's Object) |journal=Astrophysics and Space Science |date=January 2002 |volume=279 |pages=5–14 |doi=10.1023/A:1014627418565 |arxiv=astro-ph/0102346 |bibcode=2002Ap&SS.279....5D |s2cid=18267843 |url=https://ui.adsabs.harvard.edu/abs/2002Ap&SS.279....5D |access-date=12 March 2022}}</ref>

}}

==External links==
* [http://www.aavso.org/vsots_v4334sgr AAVSO Variable Star of the Month. V4334 Sgr (Sakurai's Object): June 2002]

{{Stars of Sagittarius}}

{{DEFAULTSORT:Sakurai's Object}}
[[Category:Stellar evolution]]
[[Category:Sagittarius (constellation)]]
[[Category:Objects with variable star designations|Sagittarii, V4334]]
[[Category:Novae]]
[[Category:2MASS objects|J17523269-1741080]]
[[Category:F-type supergiants]]
[[Category:Astronomical objects discovered in 1996]]