First Detection of $^3$He$^+$ in the Planetary Nebula IC$\,$418
  The $^3$He isotope is important to many fields of astrophysics, including
stellar evolution, chemical evolution, and cosmology. The isotope is produced
in low-mass stars which evolve through the planetary nebula (PN) phase. $^3$He
abundances in PNe can help test models of the chemical evolution of the Galaxy.
We present the detection of the $^3$He$^+$ emission line using the single dish
Deep Space Station 63, towards the PN IC$\,$418. We derived a $^3$He/H
abundance in the range 1.74$\pm$0.8$\times$10$^{-3}$ to
5.8$\pm$1.7$\times$10$^{-3}$, depending on whether part of the line arises in
an outer ionized halo. The lower value for $^3$He/H ratio approaches values
predicted by stellar models which include thermohaline mixing, but requires
that large amounts of $^3$He are produced inside low-mass stars which enrich
the interstellar medium (ISM). However, this over-predicts the $^3$He abundance
in HII regions, the ISM, and proto-solar grains, which is known to be of the
order of 10$^{-5}$. This discrepancy questions our understanding of the
evolution of the $^3$He, from circumstellar environments to the ISM.
