  Using the ambitwistor string, we compute tree-level celestial amplitudes for
biadjoint scalars, Yang-Mills and gravity to all multiplicities. They are
presented in compact CHY-like formulas with operator-valued scattering
equations and numerators acting on a generalized hypergeometric function. With
these we extend the celestial double copy to tree-level amplitudes with
arbitrary number of external states. We also show how color-kinematics duality
is implemented in celestial amplitudes and its interpretation in terms of a
generalized twisted cohomology theory.
