IC 4997

IC 4997

Emission nebula
Planetary nebula
Observation data: J2000 epoch
Right ascension	20h 20m 08.76s [1]
Declination	+16° 43′ 53.7″ [1]
Distance	14,090 (4,320 pc) [2]   ly
Apparent magnitude (V)	11.15 [1]
Apparent dimensions (V)	2.7″ x 1.4″ [3]
Constellation	Sagitta [4]
Physical characteristics
Radius	0.092 ly
Notable features	Bipolar outflow, Bipolar nebula
Designations	IC 4997 PNG 058.3-10.9 PK 058-10 1 Hen 2-464 PN ARO 38 V* QV Sge
See also: Lists of nebulae

IC 4997 is a planetary nebula located in the constellation of Sagitta. ^[4] It was discovered in 1896 by Edward Charles Pickering and Williamina Fleming, ^[5] and independently by Gustav Gruss the same year. ^[6] This nebula is about 14,000 light-years from Earth. ^[2] It looks like an ordinary star in smaller telescopes, and only detailed study of its spectrum reveals its nebular characteristics. ^[7]

Physical characteristics

IC 4997 is very young and very dense with a very high nebular temperature of around 20,000 K, ^[8] 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, ^[7] while it also reaches a maximum expansion velocity of 60 km/s relative to its central star. ^[8] Its central star has a magnitude of around 14m ^[7] and a temperature of around 47,000--59 000 K. ^[9]

The most characteristic feature of IC 4997 is its variability. ^[10] In the 1960s, there was a sudden change in its spectrum. Variability could be related to the nebula expansion ^[11] or an episodic smoothly changing stellar wind. ^[12]

See also

• List of planetary nebulae
• List of largest nebulae
• Lists of nebulae

References

1. "IC 4997". SIMBAD . Centre de données astronomiques de Strasbourg . Retrieved July 4, 2022.
2. Bailer-Jones, C. A. L.; Rybizki, J.; Fouesneau, M.; Mantelet, G.; Andrae, R. (2018). "Estimating Distance from Parallaxes. IV. Distances to 1.33 Billion Stars in Gaia Data Release 2". The Astronomical Journal . 156 (2): 58. arXiv: 1804.10121 . Bibcode:2018AJ....156...58B. doi: 10.3847/1538-3881/aacb21 . S2CID   119289017.
3. Miranda, Luis F.; Torrelles, Jose M.; Eiroa, Carlos (1996). "The Double-Shell Structure of the Variable Young Planetary Nebula IC 4997". The Astrophysical Journal Letters . 461 (2): L111. Bibcode:1996ApJ...461L.111M. doi:10.1086/310017. S2CID   122885056.
4. "IC 4497, Hubble's Guide to Planetary Nebulae". esahubble.org.
5. Pickering, E. C.; Fleming, W. P. (1896). "Harvard College Observatory, circular no. 9. Stars having peculiar spectra". The Astrophysical Journal . 4: 142–143. Bibcode:1896ApJ.....4..142P. doi:10.1086/140257.
6. "IC 4997 in Celestial Atlas". cseligman.com.
7. "IC 4997, Jim Kaler's STARS". illinois.edu.
8. Danehkar, A.; Parthasarathy, M. (2022). "Physical conditions and chemical abundances of the variable planetary nebula IC 4997". Monthly Notices of the Royal Astronomical Society . 514 (1): 1217–1230. arXiv: 2205.14250 . Bibcode:2022MNRAS.514.1217D. doi: 10.1093/mnras/stac1364 .
9. Feibelman, W. A.; Hobbs, R. W.; McCracken, C. W.; Brown, L. W. (1979). "Reversal of the [O III] lambda 4363/Hgamma lambda 4340 ratio in the planetary nebula IC 4997". The Astrophysical Journal . 231: 111–114. Bibcode:1979ApJ...231..111F. doi: 10.1086/157167 .
10. Arkhipova, V. P.; Burlak, M. A.; Ikonnikova, N. P.; Komissarova, G. V.; Esipov, V. F.; Shenavrin, V. I. (2020). "Surprising Variability of the Planetary Nebula IC 4997 = QV Sge". Astronomy Letters . 46 (2): 100–119. arXiv: 2002.10005 . Bibcode:2020AstL...46..100A. doi:10.1134/S1063773720020012. S2CID   211259042.
11. Kiser, J.; Daub, C. T. (1982). "Physical variations in the planetary nebula IC 4997". The Astrophysical Journal . 253: 679–681. Bibcode:1982ApJ...253..679K. doi:10.1086/159668.
12. Miranda, Luis F.; Torrelles, José M.; Lillo-Box, Jorge (2022). "An episodically variable stellar wind in the planetary nebula IC 4997". Astronomy & Astrophysics . 657: L9. arXiv: 2112.13607 . Bibcode:2022A&A...657L...9M. doi:10.1051/0004-6361/202142730. S2CID   245502764.