The Lyman resonance-absorption bands of interstellar molecular hydrogen have been observed in the far-ultraviolet spectrum of the star Persei. The column density of H2 is estimated to be about 1.3 X 1O cm . The colurnn density of interstellar atomic hydrogen, determined from the La absorption line in the same spectrum, is about 4.2 >c 1 cm . Hence, in this line of sight, where visual total extinction by dust is about 1 mag, nearly half of the total hydrogen may be in molecular form. This is in agreement with theoretical predictions.
No takes yet. Share an insight, caveat, or question.
George R. Carruthers (1970) studied this question.