Dipole Anisotropy in the COBE DMR First-Year Sky Maps

We present a determination of the cosmic microwave background dipole amplitude and direction from the COBE Di(cid:11)erential Microwave Radiometers (DMR) (cid:12)rst year of data. Data from the six DMR channels are consistent with a Doppler-shifted Planck function of dipole amplitude (cid:1)T = 3:365 (cid:6) 0:027 direction (l II ;b II ) The implied velocity of the Local Group with respect to the CMB rest frame is ~vLG = 627 (cid:6) 22 km s (cid:0)1 toward (l II ;b II ) = (276 (cid:14) (cid:6) 3 (cid:14) ;30 (cid:14) (cid:6) 3 (cid:14) ). DMR has also mapped the dipole anisotropy resulting from the Earth's orbital motion about the Solar system barycenter, yielding a measurement of the monopole CMB temperature T0 at 31.5, 53, and 90 GHz, T0 = 2:75 (cid:6) 0:05 K.