This element was first isolatod by J. Berzelius in 1824 in Stockholm, Sweden. The name comes from the mineral zirconia. In Arabic zargun means golden colour.

Ionization energies
ZrI 6.8 eV, ZrII 13.1 eV, ZrIII 23.0 eV.

Absorption lines of ZrI

Table 1. Equivalent widths of ZrI 6127(2)

Group V III Ib

G2 0.002   0.015
S 0.004    
G5     0.033,0.101
G8   0.038 0.082
K0   0.032  
K2   0.053 0.175
K3   0.144 0.195
K5 0.052   0.209
M0   0.141  

ZrI (see for instance the line at 6127) appears in G-type stars and grows toward later types. There is a positive luminosity effect.

Figure 63

Emission lines of Zrl
Some ZrI lines appear in emission during the decreasing light of a long-period variable. Their great intensity is probably due to fluorescence (Merrill 1953).

Absorption lines of ZrII

Table 2. Equivalent widths of ZrII

  4149(41) 4211(15)

Group V Ib V Ib

B9.5 0.006      
A0 0.015      
A1     0.019  
A2     0.025  
A7     0.025  
F0   0.104(Ia) 0.055 0.104(Ia)
F2   0.083   0.083
F4     0.042  
F5 0.05 0.15 0.033 0.167
F6     0.037  
F8     0.044 0.29
G0     0.075  
G1     0.097  
G2     0.061  
S 0.062   blend CH  
K5 0.088   blend CH  

ZrII (see the lines at 4211 and 4149) appears in late A-type and grows monotonically toward cooler stars. There is a positive luminosity effect.

Zr has several strong lines in the red region - 5955, 6127, 6135 (M.2 and 3) - which are characteristic of late type stars (Keenan 1957).

Behavior in non-normal stars
ZrII lines are strong in the spectra of Bp stars of the Hg-Mn subgroup. A typical value is W(4149) = 0.030 (Kodaira and Takada 1978). Redfors (1991) detected ZrIII in the ultraviolet spectra of some Bp stars of the same subgroup and Redfors and Cowley (1993) added more stars.

ZrII lines are strong in the spectra of Ap stars of the Cr-Eu-Sr subgroup (Adelman 1973b). W(4719) = 0.045 (Sadakane 1976).

In metal-weak stars Zr follows the behavior of the other metals. Magain (1989) found that, when Zr is compared with Fe, it tends to be overabundant. Typically W(4209) = 0.034 for G2V (Zhao and Magain 1991).

In globular cluster stars Zr tends to behave parallel to Fe (Wheeler et al. 1989).

Zr lines are strengthened in the spectra of Ba stars, which leads to overabundances of one order of magnitude (Lambert 1985, Smith 1984). Typical W values for Ba stars are twice as large as for normal giants (Danziger 1965). Zr lines are also strengthened in the spectra of subgiant CH stars, which are alsocalled hot Ba stars (Luck and Bond 1982).

Zr lines are strengthened in S-type stars, by factors of the order of 1.5 with respect to stars of the same temperature (Smith and Lambert 1986).

ZrI lines are very strong in C-type stars later than C 3, which probably indicates a large overabundance of Zr. W(5735) is typically about 1.0 Å(Fujita 1966). The overabundance of Zr was confirmed by Kilston (1975) and Utsumi (1984).

ZrI lines are also strong in the majority of the SC stars (Wallerstein 1989, Kipper and Wallerstein 1990).

Zr seems to be normal in the Magellanic Cloud stars (Luck and Lambert 1992).

Zr has five stable isotopes, namely Zr 90, 91, 92, 94 and 96, which occur in the solar system with the following frequencies respectively: 52%, 11%, 17%, 17% and 3%. There also exist 15 shorter lived isotopes and isomers. Among them Zr93 has a half life of 1.5 × 106 years.

Zook (1978, 1985) studied the band heads at 6930 of ZrO in two S-type stars and found about solar ratios for the stable isotopes. He found also a small amount of the unstable Zr93, which is indicative of the operation of the s process. Lambert (1988) also found solar ratios, with perhaps an excess of Zr90.

Zr 90, 91, 92 and 94 can only be made by the s process, whereas Zr96 can only be made by the r process.

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