Johannes Hevelius, Nova CK Vulpeculae (1670) and the ''hibernation'' model of cataclysmic variables

I review the basic properties of cataclysmic variables and the thermonuclear runaway (TNR) theory of the outbursts of novae, including the ''hibernation'' model of cataclysmic variables proposed recently by Livio, Prialnik, Shara and others. The TNR theory, while remarkably successful is explaining (and predicting) a number of observational properties of novae, met also with some difficulties related to excessive mass-transfer rates in old novae and conflicting estimates of their space density. Both, the mass-transfer rates and space densities, are estimated from absolute magnitudes of novae as observed within decades before, or after their outbursts. Nova CK Vulpeculae (1670), the oldest recorded nova, was observed in 1670-1672 by Hevelius, whose observations - together with those by Anthelme and Cassini - were sufficiently numerous and accurate to permit a modern reconstruction of the light curve and its classification as a very slow nova. The nova is now 6 mag fainter than other old novae and this implies a very low mass-transfer rate (dM/dt)≤ 10-12 Msun/year. CK Vul, together with a less extreme case of Nova WY Sge (1783), thus suggest that high luminosities and, hence, high accretion rates observed in more recent novae are maintained for no more than a century after outburst and that during millenia between outbursts novae ''hibernate'' at very low mass-transfer rates. 15 refs., 4 figs. (author)