We report the serendipitous detection by the XMM-Newton X-ray Observatory of an X-ray source at the position of the Type I ( He- and N-rich ) bipolar planetary nebula Hb 5 .
The Hb 5 X-ray source appears marginally resolved .
While the small number of total counts ( \sim 170 ) and significant off-axis angle of the X-ray source ( \sim 7.8 ^ { \prime } ) precludes a definitive spatial analysis , the morphology of the X-ray emission appears to trace the brightest features seen in optical images of Hb 5 .
The X-ray spectrum is indicative of a thermal plasma at a temperature between 2.4 and 3.7 MK and appears to display strong Neon emission .
The inferred X-ray luminosity is L _ { X } = 1.5 \times 10 ^ { 32 } \textrm { ergs s } ^ { -1 } .
These results suggest that the detected X-ray emission is dominated by shock-heated gas in the bipolar nebula , although we can not rule out the presence of a point-like component at the position of the central star .
The implications for and correspondence with current models of shock-heated gas in planetary nebulae is discussed .