IC 4997
{{Short description|Planetary nebula in the constellation Sagitta}}
{{Planetary nebula
| image = 300px
| name = IC 4997
| type = Planetary
| epoch = J2000
| dist_ly = 14,090 (4,320 pc)
| constellation = Sagitta
| radius_ly = 0.092
| notes = Bipolar outflow, Bipolar nebula
| names = IC 4997
PNG 058.3-10.9
PK 058-10 1
Hen 2-464
PN ARO 38
V* QV Sge
}}
IC 4997 is a planetary nebula located in the constellation of Sagitta. It was discovered in 1896 by Edward Charles Pickering and Williamina Fleming, and independently by Gustav Gruss the same year. This nebula is about 14,000 light-years from Earth. It looks like an ordinary star in smaller telescopes, and only detailed study of its spectrum reveals its nebular characteristics.
Physical characteristics
IC 4997 is very young and very dense with a very high nebular temperature of around 20,000 K, which is twice those measured in most nebulae. The mean expansion velocity of the nebula seems to be slow at 20 km/s at the outer layer, while it also reaches a maximum expansion velocity of 60 km/s relative to its central star. Its central star has a magnitude of around 14m and a temperature of around 47,000--59 000 K.
The most characteristic feature of IC 4997 is its variability. In the 1960s, there was a sudden change in its spectrum.
Variability could be related to the nebula expansion or an episodic smoothly changing stellar wind.
See also
References
{{reflist|refs =
{{cite simbad|title=IC 4997|access-date=July 4, 2022}}
{{cite journal | last1=Pickering | first1=E. C. | last2=Fleming | first2=W. P. | date=1896 | title=Harvard College Observatory, circular no. 9. Stars having peculiar spectra | journal=The Astrophysical Journal | volume=4 | issue= | pages=142–143 | doi=10.1086/140257 | bibcode=1896ApJ.....4..142P}}
{{cite journal | last1=Miranda | first1=Luis F. | last2=Torrelles | first2=Jose M. | last3=Eiroa | first3=Carlos| date=1996 | title=The Double-Shell Structure of the Variable Young Planetary Nebula IC 4997 | journal=The Astrophysical Journal Letters | volume=461 | issue= 2| pages=L111 | doi=10.1086/310017 | bibcode=1996ApJ...461L.111M| s2cid=122885056 }}
{{cite journal | last1=Danehkar | first1=A. | last2=Parthasarathy | first2=M. | date=2022 | title=Physical conditions and chemical abundances of the variable planetary nebula IC 4997 | journal=Monthly Notices of the Royal Astronomical Society | volume=514 | issue=1 | pages=1217–1230 | doi=10.1093/mnras/stac1364 | doi-access=free | bibcode=2022MNRAS.514.1217D|arxiv = 2205.14250 }}
{{cite journal | last1=Arkhipova | first1=V. P. | last2=Burlak | first2=M. A. | last3=Ikonnikova | first3=N. P. | last4=Komissarova | first4=G. V. | last5=Esipov | first5=V. F. | last6=Shenavrin | first6=V. I. | date=2020 | title=Surprising Variability of the Planetary Nebula IC 4997 = QV Sge | journal=Astronomy Letters | volume=46 | issue=2 | pages=100–119 | doi=10.1134/S1063773720020012 | bibcode=2020AstL...46..100A|arxiv = 2002.10005 | s2cid=211259042 }}
{{cite journal | last1=Kiser | first1=J. | last2=Daub | first2=C. T. | date=1982 | title=Physical variations in the planetary nebula IC 4997 | journal=The Astrophysical Journal | volume=253 | issue= | pages=679–681 | doi=10.1086/159668 | bibcode=1982ApJ...253..679K}}
{{cite journal | last1=Miranda | first1=Luis F. | last2=Torrelles | first2=José M. | last3=Lillo-Box | first3=Jorge | date=2022 | title=An episodically variable stellar wind in the planetary nebula IC 4997 | journal=Astronomy & Astrophysics | volume=657 | issue= | pages=L9 | doi=10.1051/0004-6361/202142730 | bibcode=2022A&A...657L...9M|arxiv = 2112.13607 | s2cid=245502764 }}
{{cite journal | last1=Bailer-Jones | first1=C. A. L. | last2=Rybizki | first2=J. | last3=Fouesneau | first3=M. | last4=Mantelet | first4=G. | last5=Andrae | first5=R. | date=2018 | title=Estimating Distance from Parallaxes. IV. Distances to 1.33 Billion Stars in Gaia Data Release 2 | journal=The Astronomical Journal | volume=156 | issue=2 | pages=58 | doi=10.3847/1538-3881/aacb21 | bibcode=2018AJ....156...58B|arxiv = 1804.10121 | s2cid=119289017 | doi-access=free }}
{{cite journal | last1=Feibelman | first1=W. A. | last2=Hobbs | first2=R. W. | last3=McCracken | first3=C. W. | last4=Brown | first4=L. W. | date=1979 | title=Reversal of the [O III] lambda 4363/Hgamma lambda 4340 ratio in the planetary nebula IC 4997| journal=The Astrophysical Journal | volume=231 | issue= | pages=111–114 | doi=10.1086/157167 | bibcode=1979ApJ...231..111F | doi-access=free }}
}}
{{sky|20|20|08.76|+|16|43|53.7|2100}}
{{Sagitta}}
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