Publication Date:
2016-05-05
Description:
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 ± 0.8 x 10 –3 to 5.8 ± 1.7 x 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 overpredicts the 3 He abundance in H ii regions, the ISM, and protosolar 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.
Print ISSN:
1745-3925
Electronic ISSN:
1745-3933
Topics:
Physics
Permalink