27 Dec
2010
27 Dec
'10
3:13 p.m.
Mike: We know about the solar wind because of particle detectors like the one listed in the upper left column on SpaceWeather.com. It's proton and electrons in a plasma too hot to form atoms of hydrogen. We see planetary nebulae because an old star has balooned up to a giant phase and sloughed off its outer mantle containing mostly hydrogen but also many atoms of oxygen nitrogen and sulphur. These atoms are seen by us because they are excited by the ultraviolet light of the exposed core of the old star. These atoms emit light in narrow bands which we can see in the light spectrum. DT