1. NGC 7023 is in Cepheus
2. NGC 7023 is a Photodissociation Region -- Now
3. but it didn't get that way by photodissociation
4. 5000 years ago (from this Monday) a bipolar outflow
5. cleared away the circumstellar cocoon
6. and exposed the outflow relic
7. to dissociating UV photons

What does this have to do with the origin of H and Galactic Ecology?

• initial mass function: there are more intermediate mass stars than massive ones
• these stars are in pre-ms phase a longer time
• most of the atomic gas in our Galaxy has been processed (outflow, then PD) by stars like HD 200775

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