  In stars with temperatures above 20*10^6 K, hydrogen burning is dominated by
the CNO cycle. Its rate is determined by the slowest process, the
14N(p,gamma)15O reaction. Deep underground in Italy's Gran Sasso laboratory, at
the LUNA 400 kV accelerator, the cross section of this reaction has been
measured at energies much lower than ever achieved before. Using a windowless
gas target and a 4pi BGO summing detector, direct cross section data has been
obtained down to 70 keV, reaching a value of 0.24 picobarn. The Gamow peak has
been covered by experimental data for several scenarios of stable and explosive
hydrogen burning. In addition, the strength of the 259 keV resonance has been
remeasured. The thermonuclear reaction rate has been calculated for
temperatures 90 - 300 *10^6 K, for the first time with negligible impact from
extrapolations.
