Chandra observations of the X-ray jet of 3C 273

We report results from Chandra observations of the X-ray jet of 3C 273 duri ng the calibration phase in 2000 January. The zeroth-order images and spect ra from two 40 ks exposures with the High-Energy Transmission Grating and L ow-Energy Transmission Grating + Advanced CCD Imaging Spectrometer-S show a complex X-ray structure. The brightest optical knots are detected and reso lved in the 0.2-8 keV energy band. The X-ray morphology tracks well the opt ical. However, while the X-ray brightness decreases along the jet, the oute r parts of the jet tend to be increasingly bright with increasing wavelengt h. The spectral energy distributions of four selected regions can best be e xplained by the inverse Compton scattering of (beamed) cosmic microwave bac kground photons. The model parameters are compatible with equipartition and a moderate Doppler factor, which is consistent with the one-sidedness of t he jet. Alternative models either imply implausible physical conditions and energetics (the synchrotron self-Compton model) or are sufficiently ad hoc to be unconstrained by the present data (synchrotron radiation from a spat ially or temporally distinct particle population).