Univ Massachusetts, Dept Astron, Amherst, MA 01003 USA
; Chinese Acad Sci, Inst High Energy Phys, Lab Cosm Ray & High Energy Astrophys, Beijing 100039, Peoples R China
; Max Planck Inst Extraterr Phys, D-85741 Garching, Germany
; Ctr Etud Saclay, DAPNIA, DSM, Serv Astrophys, F-91191 Gif Sur Yvette, France
We present a Chandra Advanced CCD Imaging Spectrometer observation of supernova remnant G54.1+0.3. This supernova remnant is resolved into several distinct X-ray-emitting components: a central bright pointlike source (CXOU J193030.13+185214.1), a surrounding ring, bipolar elongations, plus low surface brightness diffuse emission. The spectra of these components are all well described by power-law models; the spectral index steepens with increasing distance from the pointlike source. We find no evidence for any thermal plasma emission that would correspond to shocked interstellar medium or ejecta. The observed morphological and spectral characteristics suggest that G54.1+0.3 is the closest "cousin" of the Crab Nebula-a pulsar wind nebula driven by a combination of equatorial and polar outflows from the putative pulsar represented by the pointlike X-ray source.