The Behaviour of Chemical Elements in Stars

Neon Ne Z = 10

This element was isolated by W. Ramsay and M. Travers in 1898 in London. The name alludes to the Greek neos (new).

Ionization energies
NeI 21.6 eV, NeII 40.9 eV, NeIII 63.5 eV, NeIV 97.1 eV, NeV 126.2 eV, NeVI 157.9 eV, NeVII 207.3 eV.

Absorption lines of Ne

**Table 1.** *Equivalent widths of NeI 6402(1)*

Group	V	Ia

B3	0.084	0.170
B5		0.158

Ne I lines appear in B-type stars and are prominent in supergiants.

Emission lines of NeI
Several multiplets of Ne I (for instance 1, 3, 5 and 6) are present in the spectrum of one R CrB star (Dahari and Osterbrock 1984).

Absorption lines of NeII

**Table 2.** *Equivalent widths of NeII*

	3482(6)	3766(1)		4219(52)

Group	V	V	Ia	V	III	Ia

O9				0.025
O9.5	0.039
B0	0.042	0.054	0.100	0.046	0.035	0.033
B0.5		0.053		0.027
B2					0.015

Source: Some values for 4219 are from Kilian and Nissen (1989).

Ne II lines appear in late O-type and early B-type stars, being slightly stronger in supergiants.

Emission lines of Ne V
The lines at 1136 and 1145 are seen in emission in the solar ultraviolet spectrum.

Emission lines of Ne VI
Four NeVI lines between 997 and 1010 are seen in emission in the solar ultraviolet spectrum (Feldman and Doschek 1991).

Behavior in non-normal stars
Ne lines are very strong in extreme helium stars Jeffery and Heber 1993). NeI lines are very strong in the spectrum of the A-tvpe He-strong star upsilon Sgr (Greenstein 1943).

[NeIII], [NeIV] and [NeV] lines are sometimes present in the nebular phase of the spectral evolution of novae Joy and Swings 1945, Warner 1989). Smits (1991) has called attention to a group of novae that have large overabundances of Ne, as well as of at least one of the elements Na, Al, Mg and Si. Andreae (1993) calls this group O-Ne-Mg stars and finds that the overabundance of Ne reaches one order of magnitude.

In symbiotic stars lines of [NeIII] and [NeIV] have been observed (Merrill 1950, Freitas Pacheco and Costa 1992). In several stars of this group Wallerstein et al. (1991) report also the presence of [NeV].

Isotopes
Ne has three stable isotopes, Ne 20, 21 and 22, and five unstable isotopes. In the solar system the stable isotopes contribute 90.5%, 0.3% and 9.2% respectively.

Origin
Ne²⁰ can be produced by carbon burning. Ne²¹ can also arise from this process or from explosive nucleosynthesis. Ne²² is produced by either helium or nitrogen burning.

Published in "The Behavior of Chemical Elements in Stars", Carlos Jaschek and Mercedes Jaschek, 1995, Cambridge University Press.