  We propose the late-O, early-B star IRS2b as the ionizing source of the Flame
Nebula (NGC 2024). It has been clear that such a hot, massive star must be
present in this heavily obscured region, and now it has been identified. New
near-infrared photometry shows that IRS2b is the most luminous and hottest star
in the young star cluster embedded in the center of NGC 2024. The near-infrared
observations (5' x 5') cover ~90 % of the HII region detected in radio
continuum radiation, making the probability very low that the ionizing star is
not present in the field. A K-band spectrum of IRS2b obtained with ISAAC on the
Very Large Telescope indicates that the spectral type of IRS2b is in the range
O8V - B2V. Additional arguments indicate that its spectral type is likely
closer to O8 than to B2. The corresponding amount of ionizing radiation is
consistent with published radio continuum and recombination line observations.
