Do All Low-Mass Stars Undergo Extra Mixing Processes?

Standard stellar evolution models that only consider convection as a physical process to mix material inside of stars predict the production significant amounts 3He in low-mass (M < 2 Msun), with peak abundances 3He/H ~ few x 10-3 by number. Over life-time Galaxy, this ought produce diminish increasing Galactocentric radius. Observations 3He+ HII regions throughout Galactic disk, however, reveal very little variation abundance values similar primoridal abundance, (3He/H)p 10-5 . This discrepancy, known "3He Problem", can be resolved invoking an extra-mixing mechanism due thermohaline instability. Here, we observe planetary nebula J320 (PN G190.3-17.7) Jansky Very Large Array (JVLA) confirm previous detection made VLA supports standard yields. measurement alone indicates not all undergo extra mixing. Our more sensitive observations do detect emission from RMS noise 58.8 microJy/beam after smoothing data velocity resolution 11.4 km/s We estimate limit <= 2.75 number using numerical radiative transfer code NEBULA. result nullifies last PN and allows for possibility mixing processes.