The Optical Morphology of the Young Planetary Nebula M1-5
Session 51 -- Planetary Nebulae
Display presentation, Thursday, January 13, 9:30-6:45, Salons I/II Room (Crystal Gateway)

## [51.05] The Optical Morphology of the Young Planetary Nebula M1-5

M. Bobrowsky (CTA)

HST images of the young planetary nebula (PN) M1-5 are presented. Although this object was identified as a PN several decades ago, until recently its small size precluded optical investigations of its morphology. Radio observations indicated an apparent angular size of 2" which, by itself, could simply have been the result of a large distance. But optical spectra showed that the electron density is high (1-3 x $10^{4}$) and radio data indicated a high emission measure, implying that the PN is young, compact, and perhaps, ionization-bounded.

Narrow-band images in $H\beta$ and [O III]$5007\AA$ show a mildly bipolar nebula. The dimensions of the nebula are approximately 1."9 x 2."6, with the major axis running roughly north-south. However, the two poles appear (in projection) $155\deg$ apart, not the $180\deg$ expected from an axially symmetric bipolar nebula. The deviation from axial symmetry could be the result of asymmetric mass loss or it could result from the interaction of the nebula with the interstellar medium.

At an estimated distance of 2.1 kpc, the size of M1-5 is only 0.019 x 0.026 pc. Small, young PNe evolve very quickly. (E.g., a similar object, Hen 1357, became a PN only during the past few decades.) Therefore it is not surprising that our observed [O III]$5007\AA$/$H\beta$ line ratio is higher (at 4.8) than previously observations indicated.

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.