Abstract
TARAFDAR and Wickramasinghe1 suggested that the Lyman alpha (Lα) intensity in the interstellar medium may be in the range (1-4) × 10-4 erg cm -2 s-1 sr-1 and have pointed out that, if this is the case, Lα may play an important part in photoemission from interstellar grains. Here we argue that typical Lα intensities in interstellar HI are significantly less than 1 × 10 -4 erg cm -2 s-1 sr-1, considering three principal sources: photoionised HII regions; shock-heated gas; and collisional excitation and recombination in interstellar HI.
Original language | English (US) |
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Pages (from-to) | 730-731 |
Number of pages | 2 |
Journal | Nature |
Volume | 271 |
Issue number | 5647 |
DOIs | |
State | Published - Dec 1 1978 |
Externally published | Yes |
All Science Journal Classification (ASJC) codes
- General