Passage: The detection of the first H+3 emission lines was reported in 1989 by Drossart et al., found in the ionosphere of Jupiter. Drossart found a total of 23 H+3 lines with a column density of 1.39×109/cm2. Using these lines, they were able to assign a temperature to the H+3 of around 1,100 K (830 °C), which is comparable to temperatures determined from emission lines of other species like H2. In 1993, H+3 was found in Saturn by Geballe et al. and in Uranus by Trafton et al.

Question: What was the column density of the 23 H=3 lines found by Drossart?
1.39×109/cm2