V1668 Cygni was a nova that appeared in the northern constellation of Cygnus, situated a couple of degrees to the southeast of the star Rho Cygni.[7] It was discovered by Canadian variable star observer Warren Morrison on September 10, 1978,[8] and reached a peak brightness of around 6.22 apparent magnitude on September 12.[2] The luminosity of the source at this time was about 100,000 times the brightness of the Sun, and likely remained at that level for several months. The expansion velocity of the nova shell was deduced through spectroscopy to be 1,300 km/s.[9]

V1668 Cygni
Location of V1668 Cygni (circled in red)
Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Cygnus
Right ascension 21h 42m 35.22s[1]
Declination +44° 01′ 54.9″[1]
Apparent magnitude (V) 6.2 (max)[2]
Variable type Nova[3]
Distance17,600 ly
(5,400[4] pc)
Absolute magnitude (MV)−7.5±0.5[5] (max)
White dwarf
Mass0.98[4] M
Other designations
Nova Cyg 1978, AAVSO 2138+43B, V1668 Cyg[6]
Database references
The light curve of V1668 Cygni, plotted from AAVSO data

After peak brightness, the lightcurve showed a smooth power-law decline with no major fluctuations.[10] The decline in brightness was rapid, dropping by three magnitudes in 24 days.[11] An optically thin shell of dust was created by the outburst that reached peak opacity after 50–60 days. The lack of a silicate feature in the infrared spectrum of this shell suggests the dust grains consisted of graphite, possibly condensed on atoms of cohenite.[9] A 1994 analysis of the light curve showed the mass of the white dwarf source is about equal to the Sun.[12]

Warren Morrison was awarded the 1979 Ken Chilton prize of the RASC primarily for this discovery.[13]


  1. ^ a b Downes, Ronald A.; et al. (June 2001). "A Catalog and Atlas of Cataclysmic Variables: The Living Edition". The Publications of the Astronomical Society of the Pacific. 113 (784): 764–768. arXiv:astro-ph/0102302. Bibcode:2001PASP..113..764D. doi:10.1086/320802.
  2. ^ a b Morrison, W.; et al. (September 1978). Marsden, B. G. (ed.). "Nova Cygni 1978". IAU Circular. 3264 (3). Bibcode:1978IAUC.3264....3M.
  3. ^ Samus, N. N.; Durlevich, O. V.; et al. (2009). "VizieR Online Data Catalog: General Catalogue of Variable Stars (Samus+ 2007-2013)". VizieR On-line Data Catalog: B/GCVS. Originally Published in: 2009yCat....102025S. 1: B/gcvs. Bibcode:2009yCat....102025S.
  4. ^ a b Hachisu, Izumi; Kato, Mariko (June 2019). "A Light-curve Analysis of 32 Recent Galactic Novae: Distances and White Dwarf Masses". The Astrophysical Journal Supplement Series. 242 (2): 138. arXiv:1905.10655. Bibcode:2019ApJS..242...18H. doi:10.3847/1538-4365/ab1b43. 18.
  5. ^ Slovak, M. H.; Vogt, S. S. (1979). "Interstellar reddening and distance of Nova Cygni 1978". Nature. 277 (5692): 114–6. Bibcode:1979Natur.277..114S. doi:10.1038/277114a0. S2CID 4330498.
  6. ^ "NOVA Cyg 1978". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2021-01-09.
  7. ^ Sinnott, Roger W.; Perryman, Michael A. C. (1997). Millennium Star Atlas. Vol. 3. Sky Publishing Corporation and the European Space Agency. p. 1124. ISBN 0-933346-83-2.
  8. ^ Smith, S. E.; et al. (December 1979). "The spectral development of nova CYG 1978". Publications of the Astronomical Society of the Pacific. 91: 775–780. Bibcode:1979PASP...91..775S. doi:10.1086/130586.
  9. ^ a b Gehrz, R. D.; et al. (July 1980). "The optically thin dust shell of nova CYG 1978". Astrophysical Journal. 239: 570–580. Bibcode:1980ApJ...239..570G. doi:10.1086/158143.
  10. ^ Strope, Richard J.; et al. (July 2010). "Catalog of 93 Nova Light Curves: Classification and Properties". The Astronomical Journal. 140 (1): 34–62. arXiv:1004.3698. Bibcode:2010AJ....140...34S. doi:10.1088/0004-6256/140/1/34.
  11. ^ Klare, G.; et al. (September 1980). "Spectral evolution of nova CYG 1978". Astronomy and Astrophysics. 89: 282–290. Bibcode:1980A&A....89..282K.
  12. ^ Kato, M. (January 1994). "Theoretical light curve for a classical nova : nova Cygni 1978". Astronomy and Astrophysics. 281: L49–L52. Bibcode:1994A&A...281L..49K.
  13. ^ Broughton, Peter. "Warren Morrison". Royal Astronomical Society of Canada. Retrieved 2021-01-09.