Editing Stingray Nebula

{{Short description|Planetary nebula in the constellation Ara}}
{{Planetary nebula
| image         = [[Image:stingraynebula.jpg|250px]]
| caption       = Hubble Space Telescope photograph
| name          = Stingray Nebula
| type          = Planetary
| epoch         = [[J2000]]
| ra            = {{RA|17|16|21.071}}<ref name=SIMBAD>{{cite web |url=http://simbad.u-strasbg.fr/simbad/sim-id?protocol=html&Ident=Stingray+Nebula |title=Results for Stingray Nebula |author=SIMBAD |author-link=SIMBAD |date=15 January 2007 |website=SIMBAD, Centre de Données Astronomiques de Strasbourg}}</ref>
| dec           = {{DEC|-59|29|23.64}}<ref name=SIMBAD/>
| dist_ly       = 18,000
| dist_pc       = 5,600<ref name=Bobrowsky1994/>
| appmag_v      = 10.75<ref name=SIMBAD/>
| size_v        = 1″.6<ref name=Bobrowsky1994/>
| constellation = [[Ara (constellation)|Ara]]
| radius_ly     = 0.08<ref name=Bobrowsky1994/>
| absmag_v      =
| notes         =
| names         = PN G331.3-12.1,<ref name=SIMBAD/><br/>Hen 3-1357<ref name=SIMBAD/>
}}
The '''Stingray Nebula''' (Hen 3-1357) is the youngest-known [[planetary nebula]], having appeared in the 1980s.<ref name=Bobrowsky1994>{{cite journal |last=Bobrowsky |first=M. |date=1994 |title=Narrowband HST imagery of the young planetary nebula Henize 1357 |journal=[[The Astrophysical Journal]] |volume=426 |pages=L47–L50 |bibcode=1994ApJ...426L..47B |bibcode-access=free |doi=10.1086/187336|doi-access=free }}</ref> The nebula is located in the direction of the [[Southern celestial hemisphere|southern]] [[constellation]] [[Ara (constellation)|Ara]] (the Altar), and is located {{convert|5600|pc|ly|abbr=off|lk=on|order=flip}} away. Although it is some 130 times the size of the [[Solar System]], the Stingray Nebula is only about one tenth the size of most other known planetary nebulae.  The central [[star]] of the nebula is the fast-evolving star SAO 244567.  Until the early 1970s, it was observed on Earth as a [[preplanetary nebula]] in which the gas had not yet become hot and ionized.

The image of the nebula shows how the older outer shells of gas are acting as a [[collimator]] for the more recent gas outflow from the central star—an important observation, as this process has not been well understood.{{citation needed|date=May 2021}}

==History==

Prior to the discovery of the nebula, its central star was known as He 3-1357, which [[Karl Gordon Henize]] classified as an A- or B-type [[Hα]] [[emission-line]] star in 1976. It was observed in 1971 to be [[post-asymptotic giant branch]] B1 or B2 [[supergiant]]. Planetary nebula emission lines were identified in this star in 1989 by the [[International Ultraviolet Explorer]].<ref name="Parthasarathy1995">{{cite journal |bibcode=1995A&A...300L..25P |title=Fading and variations in the spectrum of the central star of the very young planetary nebula SAO 244567 (Hen 1357) |last1=Parthasarathy |first1=M. |last2=Garcia-Lario |first2=P. |last3=De Martino |first3=D. |last4=Pottasch |first4=S. R. |last5=Kilkenny |first5=D. |last6=Martinez |first6=P. |last7=Sahu |first7=K. C. |last8=Reddy |first8=B. E. |last9=Sewell |first9=B. T. |journal=Astronomy and Astrophysics |year=1995 |volume=300 }}</ref> As the nebula would be newly formed and very small, ground-based observations were not able to resolve it; so Bobrowsky observed it with the [[Hubble Space Telescope]], discovering the nebula, which he named the "Stingray Nebula".<ref name=Bobrowsky1994/>

In 1993, M. Parthasarathy ''et al.'' looked at the history of measurements of the brightness of the central star, and concluded that it was fading in the optical region of the spectrum.<ref name="Parthasarathy"/> It was given its [[variable star designation]], V839 Arae, in 1997.<ref name="Kazarovets"/>

[[File:V839AraLightCurve.png|thumb|left|A [[Photometric_system#Photometric_letters|blue band]] [[light curve]] for V839 Arae (the central star of the Stingray Nebula) adapted from Schaefer and Edwards (2015)<ref name="Schaefer"/>]]
In 1995 the central planetary nebula nucleus was observed as a DA [[white dwarf]], having seemingly faded by a factor of three between 1987 and 1995. The white dwarf has an estimated mass of {{Solar mass|link=y|0.6}} and luminosity of {{Solar luminosity|link=y|3,000}}<ref>{{cite journal |last=Parthasarathy |first=M. |date=2000 |title=Birth and early evolution of planetary nebulae |journal=[[Bulletin of the Astronomical Society of India]] |volume=28 |pages=217–224 |bibcode= 2000BASI...28..217P |bibcode-access=free}}</ref> and has an observed companion star separated by 0.3 [[arcsecond]]. The mass of the nebula is estimated as {{Solar mass|0.015}}.<ref name="Parthasarathy1995"/>

In 1998 Bobrowsky et al. described how the Hubble Space Telescope observations revealed a 17th-magnitude companion to the Stingray's 15th-magnitude central star.<ref>{{cite journal |last1=Bobrowsky |first1=M. |last2=Sahu |first2=K. C. |last3=Parthasarathy |first3=M. |last4=García-Lario |first4=P. |date=1998 |title=Birth and early evolution of a planetary nebula |journal=[[Nature (journal)|Nature]] |volume=392 |issue=6675 |pages=469–471 |bibcode=1998Natur.392..469B |doi=10.1038/33092 |arxiv=astro-ph/9804022|s2cid=4424808 }}</ref>

The central star is unusual in that it has brightened and faded over a period of 20 years. Its temperature went up by 40,000 °C. An explanation for this is that it has undergone a [[helium flash]].<ref>{{cite web |url=http://phys.org/news/2016-09-astronomers-star-reborn.html |title=Astronomers observe star reborn in a flash |date=13 September 2016 |website=Phys.org |access-date=18 September 2016}}</ref>

In January 2021, NASA discovered that the nebula had been fading since the 1990s, when it reached its peak brightness.<ref>{{cite web |url=https://www.space.com/stingray-nebula-fading-fast-hubble-photos |title=The Stingray nebula is fading fast, Hubble telescope photos reveal |first=Samantha |last=Mathewson |date=8 January 2021 |website=Space.com |access-date=8 January 2021}}</ref> Previously [[photoionization|photoionized]], the positive ions of the nebula have been recombining with the electrons.<ref>{{cite journal|doi=10.3847/1538-4357/abcc61|title=The Decline and Fall of the Youngest Planetary Nebula |year=2021 |last1=Balick |first1=Bruce |last2=Guerrero |first2=Martín A. |last3=Ramos-Larios |first3=Gerardo |journal=The Astrophysical Journal |volume=907 |issue=2 |page=104 |arxiv=2009.01701 |bibcode=2021ApJ...907..104B |s2cid=228443528 |doi-access=free }}</ref> In a NASA statement a team member, Martín A. Guerrero of the [[Instituto de Astrofísica de Andalucía]] in Granada, Spain, said: "This is very, very dramatic, and very weird. What we're witnessing is a nebula's evolution in real time. In a span of years, we see variations in the nebula. We have not seen that before with the clarity we get with this view."<ref>{{cite web |url=http://www.nasa.gov/feature/goddard/2020/hubble-captures-unprecedented-fading-of-stingray-nebula |title=Hubble Captures Unprecedented Fading of Stingray Nebula |first=Lynn |last=Jenner |date=30 November 2020 |website=NASA |access-date=8 January 2021}}</ref>

[[File:Fading_Stingray.jpg|thumb|left|upright=1.5|Two images captured in 1996 and 2016 show the nebula dimming and changing shape.]]
{{clear}}

== References ==
{{reflist|refs=

<ref name="Schaefer">{{cite journal |last1=Schaefer |first1=Bradley E. |last2=Edwards |first2=Zachary I. |title=Photometry of the Stingray Nebula (V839 Ara) from 1889 TO 2015 across the Ionization of Its Planetary Nebula |journal=The Astrophysical Journal |date=October 2015 |volume=812 |issue=2 |page=133 |doi=10.1088/0004-637X/812/2/133 |url=https://ui.adsabs.harvard.edu/abs/2015ApJ...812..133S |access-date=12 June 2022|arxiv=1509.01202 |bibcode=2015ApJ...812..133S |s2cid=119249204 }}</ref>

<ref name="Parthasarathy">{{cite journal |last1=Parthasarathy |first1=M. |last2=Garcia-Lario |first2=P. |last3=Pottasch |first3=S. R. |last4=Manchado |first4=A. |last5=Clavel |first5=J. |last6=de Martino |first6=D. |last7=van de Steene |first7=G. C. M. |last8=Sahu |first8=K. C. |title=SAO 244567 : a post-AGB star which has turned into a planetarey nebula within the last 40 years |journal=Astronomy and Astrophysics |date=January 1993 |volume=267 |pages=L19-L22 |bibcode=1993A&A...267L..19P |url=https://articles.adsabs.harvard.edu/pdf/1993A%26A...267L..19P |access-date=25 November 2024}}</ref>

<ref name="Kazarovets">{{cite journal |last1=Kazarovets |first1=E. V. |last2=Samus |first2=N. N. |title=The 73rd Name-List of Variable Stars |journal=Information Bulletin on Variable Stars |date=April 1997 |volume=4471 |bibcode=1997IBVS.4471....1K |url=https://ibvs.konkoly.hu/pub/ibvs/4401/4471.pdf |access-date=25 November 2024}}</ref>

}}

==External links==
*{{commons category-inline}}
*[http://apod.nasa.gov/apod/ap120312.html The Scale of the Universe] ([[Astronomy Picture of the Day]] 2012 March 12)
*[http://www.constellation-guide.com/stingray-nebula-hen-3-1357-pn-g331-in-ara/ Stingray Nebula at Constellation Guide]

{{Ara (constellation)}}

{{Authority control}}

{{DEFAULTSORT:Stingray Nebula}}
[[Category:Planetary nebulae]]
[[Category:Ara (constellation)]]
[[Category:Astronomical objects discovered in 1971|?]]
[[Category:Astronomical objects discovered in 1989|?]]
[[Category:Objects with variable star designations|Arae, V839]]