View source for Astronomy:NGC 6905

{{Short description|Planetary nebula in the constellation Delphinus}}
{{ Planetary nebula |
| image = [[Image:NGC 6905 - VLT(FORS2) - RHaBOIII.png|250px]]
|caption=Image based on observations made with ESO Telescopes at the La Silla Paranal Observatory
| name = NGC 6905
| type = Planetary
| epoch = [[Astronomy:J2000|J2000]]
| ra = {{RA|20|22|23}}<ref name=simbad>{{cite simbad|title=NGC 6905|access-date=25 January 2016}}</ref>
| dec = {{DEC|+20|06|16}} <ref name=simbad/>
| dist_ly = 7.5 [[Light year|Kly]] (2.3 [[Astronomy:Parsec|Kpc]])<ref name=Keller2011/>
| appmag_v = 10.9<ref>{{cite web|title=Revised NGC Data for NGC 6905|url=http://spider.seds.org/ngc/revngcic.cgi?NGC6905|website=spider.seds.org}}</ref>
| size_v = 1.2{{prime}}
| constellation = [[Astronomy:Delphinus|Delphinus]]
| radius_ly = 
| absmag_v = 
| notes = 
| names = Blue Flash Nebula<ref name=skyhound/>}}
'''NGC 6905''', also known as the '''Blue Flash Nebula''', is a [[Astronomy:Planetary nebula|planetary nebula]] in the constellation [[Astronomy:Delphinus|Delphinus]]. It was discovered by William Herschel in 1784. The central star is 14.0 mag. The distance of the nebula, as with most planetary nebulae, is not well determined and estimates range between 1.7 and 2.6 kpc.<ref name=Keller2011>{{cite journal|last1=Keller|first1=Graziela R.|last2=Herald|first2=James E.|last3=Bianchi|first3=Luciana|last4=Maciel|first4=Walter J.|last5=Bohlin|first5=Ralph C.|title=A new grid of synthetic spectra for the analysis of [WC]-type central stars of planetary nebulae|journal=Monthly Notices of the Royal Astronomical Society|date=1 December 2011|volume=418|issue=2|pages=705–728|doi=10.1111/j.1365-2966.2011.19085.x|arxiv = 1211.0223 |bibcode = 2011MNRAS.418..705K |s2cid=85503661 }}</ref>

The shape of NGC 6905 is characterised by an internal shell with angular dimensions 47" ×34" and roughly conical extensions, with ansae-type formations along the major axis. The nucleus of the nebula possesses one of the most broad emission of O<small>VI</small> emission lines among planetary nebulae.<ref name=Cuesta1993/> Moreover, O<small>VIII</small> emission has been detected in NGC 6905.<ref>{{cite journal|last1=Feibelman|first1=Walter A.|title=The IUE Spectrum of the Planetary Nebula NGC 6905|journal=The Astrophysical Journal|date=1 January 1996|volume=472|issue=1|pages=294–307|doi=10.1086/178064|language=en|issn=0004-637X|bibcode = 1996ApJ...472..294F |doi-access=free}}</ref> The ansae were particularly intense in N<small>II</small>.<ref name=Cuesta1993>{{cite journal|author1=Cuesta, L. |author2=Phillips, J. P. |author3=Mampaso, A. |title=Spectroscopy and shock modelling of the unusual bipolar outflow NGC 6905|journal=Astronomy and Astrophysics|date=1993|volume=266|issue=1|pages=199–212|bibcode=1993A&A...267..199C }}</ref> The total mass of gas in NGC 6905 falls between {{solar mass|0.31|link=y}} and {{solar mass|0.47}}.<ref name=GomezGonzalez>{{cite journal|doi=10.1093/mnras/stab3042|arxiv=2110.09551 |title=Planetary nebulae with Wolf–Rayet-type central stars – III. A detailed view of NGC 6905 and its central star|year=2022|last1=Gómez-González|first1=V M A.|last2=Rubio|first2=G.|last3=Toalá|first3=J. A.|last4=Guerrero|first4=M. A.|last5=Sabin|first5=L.|last6=Todt|first6=H.|last7=Gómez-Llanos|first7=V.|last8=Ramos-Larios|first8=G.|last9=Mayya|first9=Y. D.|journal=Monthly Notices of the Royal Astronomical Society|volume=509|pages=974–989}}</ref>

The central star has a spectral type of [WO2], meaning it has a spectrum similar to those of [[Astronomy:Wolf–Rayet star|Wolf–Rayet star]]s and is rich in oxygen;<ref name=GomezGonzalez/> it is estimated to have a surface temperature of 150,000 K.<ref name=Keller2011/><ref>{{cite journal|last1=Keller|first1=G. R.|last2=Bianchi|first2=L.|last3=Maciel|first3=W. J.|title=UV spectral analysis of very hot H-deficient [WCE]-type central stars of planetary nebulae: NGC 2867, NGC 5189, NGC 6905, Pb 6 and Sand 3|journal=Monthly Notices of the Royal Astronomical Society|date=11 June 2014|volume=442|issue=2|pages=1379–1395|doi=10.1093/mnras/stu878|arxiv = 1405.6763 |bibcode = 2014MNRAS.442.1379K }}</ref> The spectrum also shows signs of [[Chemistry:Neon|neon]] emission lines.<ref name=GomezGonzalez/> Currently about 60% the mass of the [[Astronomy:Sun|Sun]], before becoming a planetary nebula it had a mass of about {{solar mass|1.07}}.<ref name=GomezGonzalez/> An analysis of ''[[Engineering:Gaia (spacecraft)|Gaia]]'' data suggests that the central star may be a [[Astronomy:Binary star|binary system]].<ref name=Chornay>{{cite journal|doi=10.1051/0004-6361/202140288|title=Towards a more complete sample of binary central stars of planetary nebulae with Gaia|year=2021|last1=Chornay|first1=N.|last2=Walton|first2=N. A.|last3=Jones|first3=D.|last4=Boffin|first4=H. M. J.|last5=Rejkuba|first5=M.|last6=Wesson|first6=R.|journal=Astronomy & Astrophysics|volume=648|pages=A95|arxiv=2101.01800|bibcode=2021A&A...648A..95C|s2cid=230770301}}</ref>

NGC 6905 can be detected under dark skies with a 4-inch telescope, but it better observed with larger instruments.<ref name=skyhound>{{cite web|title=The Blue Flash (NGC 6905)|url=http://observing.skyhound.com/archives/aug1/NGC_6905.html|website=observing.skyhound.com|access-date=25 January 2016}}</ref>

== References ==
{{reflist}}

== External links ==



{{DEFAULTSORT:NGC 6905}}
[[Category:Planetary nebulae]]
[[Category:Delphinus]]
[[Category:NGC objects|6905]]

{{Sourceattribution|NGC 6905}}