  We report the discovery of TeV gamma-ray emission coincident with the
shell-type radio supernova remnant (SNR) CTA 1 using the VERITAS gamma-ray
observatory. The source, VER J0006+729, was detected as a 6.5 standard
deviation excess over background and shows an extended morphology, approximated
by a two-dimensional Gaussian of semi-major (semi-minor) axis 0.30 degree (0.24
degree) and a centroid 5' from the Fermi gamma-ray pulsar PSR J0007+7303 and
its X-ray pulsar wind nebula (PWN). The photon spectrum is well described by a
power-law dN/dE = N_0 (E/3 TeV)^(-\Gamma), with a differential spectral index
of \Gamma = 2.2 +- 0.2_stat +- 0.3_sys, and normalization N_0 = (9.1 +-
1.3_stat +- 1.7_sys) x 10^(-14) cm^(-2) s^(-1) TeV^(-1). The integral flux,
F_\gamma = 4.0 x 10^(-12) erg cm^(-2) s^(-1) above 1 TeV, corresponds to 0.2%
of the pulsar spin-down power at 1.4 kpc. The energetics, co-location with the
SNR, and the relatively small extent of the TeV emission strongly argue for the
PWN origin of the TeV photons. We consider the origin of the TeV emission in
CTA 1.
