SN1972E was a supernova in the galaxy NGC 5253 that was discovered 13 May 1972 with an apparent B magnitude of about 8.5, shortly after it had reached its maximum brightness. In terms of apparent brightness, it was the second brightest supernova of any kind (fainter only than SN1987A) of the 20th Century. It was observed for nearly 700 days, and it became the prototype object for the development of theoretical understanding of Type Ia supernovae.
The supernova was discovered by Charles Kowal, about 56 arc seconds west and 85 arc seconds south of the center of NGC 5253. The position in the periphery of the galaxy aided observation, minimizing interference by background objects. Well-positioned for Southern Hemisphere observers, it was quite observable from Northern Hemisphere observatories as well. Attempts made to observe it in X-rays with UHURU and OSO-7 and to detect gamma rays from it via Cerenkov radiation showers gave at best equivocal results.
Photometric and spectroscopic measurements were made in the visible and near infrared by many observers, extending to about 700 days after maximum light. Interstellar absorption lines of ionized calcium due to gas both in our galaxy and NGC 5253 were observed, allowing an estimate of the interstellar extinction.
The extended length of the observed light curve found a remarkably uniform 0.01 magnitudes per day decline starting about 60 days after discovery. Translated into other units, this is almost exactly a 77-day half-life, which is the half-life of 56Co. In the standard model for Type Ia supernovae, approximately a solar mass of 56Ni is formed and ejected from a white dwarf which accretes mass from a binary companion and is raised over the Chandrasekhar limit and explodes. This 56Ni decays with a half-life of about 6 days to 56Co, and the decay of the cobalt provides the energy radiated away by the supernova remnant. The model also produces an estimate for the luminosity of such a supernova. The observations of SN1972e, both peak brightness and fade rate, were in general agreement with these predictions, and led to rapid acceptance of this degenerate-explosion model.
- Lee, T. A.; Wamsteker, W.; Wisniewski, W. Z.; Wdowiak, T. J. (1972). "Photometry of Supernova 1972 IN NGC 5253". Astrophysical Journal 177: L59. Bibcode:1972ApJ...177L..59L. doi:10.1086/181052.
- Jarrett, A.H. (21 Sep 1973). Information Bulletin on Variable Stars (828). Missing or empty
- Ardeberg, A.; de Groot, M. (1973). "The 1972 supernova in NGC 5253. Photometric results from the first observing season". Astronomy & Astrophysics 28: 295–304. Bibcode:1973A&A....28..295A.
- Canzares, C. R.; Neighbours, J. E.; Matilsky, T. (1974). "A Search for X-Rays from Supernova 1972e with UHURU and OSO-7". Astrophysical Journal 192: L61. Bibcode:1974ApJ...192L..61C. doi:10.1086/181591.
- Ulmer, M. P.; Baity, W. A.; Wheaton, W. A.; Peterson, L. E. (1 Nov 1974). "Upper limit to the X-ray flux from the supernova in NGC 5253 above 7 keV from the OSO-7". Astrophysical Journal 193: 535–537. Bibcode:1974ApJ...193..535U. doi:10.1086/153191.
- Grindlay, J. E.; Helmken, H. F.; Brown, R. H.; Davis, J.; Allen, L. R. (1 Oct 1975). "Results of a Southern-Hemisphere search for gamma-ray sources at energies of at least 300 GeV". Astrophysical Journal 201: 82–89. Bibcode:1975ApJ...201...82G. doi:10.1086/153861.
- Kirshner, R. P.; Oke, J. B. (15 Sep 1975). "Supernova 1972e in NGC 5253". Astrophysical Journal 200: 574–581. Bibcode:1975ApJ...200..574K. doi:10.1086/153824.
- Osmer, P. S.; Hesser, J. E.; Kunkel, W. E.; Lasker, B. M.; McCarthy, M. F. (10 July 1972). "Optical Observations of the Supernova in NGC 5253". Nature 238: 21–22. Bibcode:1972NPhS..238...21O. doi:10.1038/physci238021a0.
- Trimble, Virginia (Oct 1982). "Supernovae. Part I: the events". Reviews of Modern Physics 54: 1183–1224. Bibcode:1982RvMP...54.1183T. doi:10.1103/RevModPhys.54.1183.
- Kirshner, R. P. & Oke, J. B. Supernova 1972e in NGC 5253. Astrophysical Journal. 200. Sept. 1975, pt. 1, p. 574-581 (SAO/NASA Astrophysics Data System)
- Riess, Adam G. et al. Using Type IA Supernova Light Curve Shapes to Measure the Hubble Constant. Astrophysical Journal Letters. 438. Jan. 1995. *: Self Published version.
- First images (1972). Photo comparisons of NGC 5253 in June 1959 then in May 1972 showing first images of the actual SN 1972e explosion near NGC 5253 (Palomar Observatory blog).