A new Planetary Nebula in the outer reaches of the Galaxy
  A proper determination of the abundance gradient in the Milky Way requires
the observation of objects at large galactiocentric distances. With this aim,
we are exploring the planetary nebula population towards the Galactic
Anticentre. In this article, the discovery and physico-chemical study of a new
planetary nebula towards the Anticentre direction, IPHASX J052531.19+281945.1
(PNG 178.1-04.0), is presented. The planetary nebula was discovered from the
IPHAS survey. Long-slit follow-up spectroscopy was carried out to confirm its
planetary nebula nature and to calculate its physical and chemical
characteristics. The newly discovered planetary nebula turned out to be located
at a very large galactocentric distance (D_GC=20.8+-3.8 kpc), larger than any
previously known planetary nebula with measured abundances. Its relatively high
oxygen abundance (12+log(O/H) = 8.36+-0.03) supports a flattening of the
Galactic abundance gradient at large galactocentric distances rather than a
linearly decreasing gradient.
