30'' × 30'' X-ray image in the energy band 0.3–8 keV around PSR J2021+4026 as seen by the Chandra ACIS-S3 CCD. The X-ray position as determined by Weisskopf et al. (2011) is illustrated by the black cross. The binning factor of the image is 05 and has been adaptively smoothed to achieve a minimum signal-to-noise ratio of 3. A nebular structure extending to the west from the pulsar can be clearly seen. The white arrow illustrates the speculated proper motion direction by extrapolating the nominal center of G78.2+2.1 to the current pulsar position.