Chemical Abundances in Planetary Nebulae
1978 ◽
Vol 76
◽
pp. 215-224
◽
Keyword(s):
Type Ii
◽
PN can be divided into four types depending on their chemical composition. In order of decreasing heavy element abundances the types are: I) He and N rich, II) intermediate population, III) high velocity, and IV) halo population. The type II PN are overabundant in N and C relative to the Orion Nebula. Well defined gradients across the galactic disk of He, N and O are derived from type II PN; the oxygen gradient is similar to the metallicity gradient derived from GK giants and F main sequence stars. By comparing the O, Ne and S abundances of PN of types III and IV with the Fe abundances of stars of similar population it is found that the O, Ne and S enrichment in the Galaxy probably took place before the Fe enrichment.
2009 ◽
Vol 5
(S262)
◽
pp. 127-130
2009 ◽
Vol 5
(S268)
◽
pp. 387-394
Keyword(s):
2009 ◽
Vol 5
(S266)
◽
pp. 421-421
1990 ◽
Vol 102
◽
pp. 726
◽
2018 ◽
Vol 14
(S344)
◽
pp. 122-124
Keyword(s):
1977 ◽
Vol 45
◽
pp. 177-179
Keyword(s):