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HST images of the young planetary nebula (PN) Henize 1475 are presented. Although this object was described as an emission line B star by Henize, until recently its small size precluded optical investigations of the morphology of the nebula. Hen 1475 was included in an HST snapshot survey of known or possible young planetary or protoplanetary nebulae because (1) similarities have been noted between emission line B stars and protoplanetary nebulae and (2) the far-infrared IRAS flux distributions and colors for Hen 1475 have been observed to be similar to those observed in young planetary nebulae.
Narrow-band images in H$\beta$ and [O III]5007\AA show a very asymmetric nebula. The nebula extends from southeast to northwest, with approximate dimensions 1."3 x 1."7. However, the unresolved 0."2 core is centered only 0."3 from the SE end of the nebula and 1."4 from the NW end. This asymmetry gives the nebula a cometary appearance. Such a morphology could result from the interaction of a moving PN with the interstellar medium (Borkowski et al., 1990; Soker et al., 1991).
At an estimated distance of 2.5 kpc, the radius of Hen 1475 is only 0.008 pc. Further evidence of the young age of Hen 1475 comes from the H$\beta$ and [O III]5007\AA fluxes. The 5007$\AA$/H$\beta$ line ratio is only 0.9 -- barely enough to qualify as excitation class 1!
Based on observations with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS5-26555. Support for this work was provided by NASA through grant number GO-3603.01-91A from the Space Telescope Science Institute.
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