The most common source for ionization are high-energy photons emitted from a nearby hot star. ... Do you like Astronomy?Maybe you are not. We think that astronomy is boring subject.But! ... Nebula is celestial object shown by cloud form because gas and some dust such as hydrogen and helium
Committee on AstronomyandAstrophysics, Board on Physics andAstronomy, Space Studies Board, National ... abstracts from the AstronomyandAstrophysics main Journal, and Supplement Series, approximately four ... AstronomyandAstrophysics Supplement Series (A&AS)- http://www.edpsciences.com/docinfos/AAS/OnlineAAS.htmlA