Franco, Tenorio-Tagle, and Bodenheimer found that the production of this material propagates outward exponentially, and a critical value of three halves characterizes the exponential "w" factor of expansion; for values exceeding the critical value of "w," this material is produced supersonically in the so-called "champagne phase." Around class O and B stars, the cloud of this material is known as the Stromgren Sphere. Areas in which this material abounds can contain Bok Globules. Its presence characterizes the evolution of a GMC to a type of region named for this material, and the Lyman Alpha 
Franco, Tenorio-Tagle, and Bodenheimer found that the production of this material propagates outward exponentially, and a critical value of three halves characterizes the exponential "w" factor of expansion; for values exceeding the critical value of "w," this material is produced supersonically in the so-called "champagne phase." Around class O and B stars, the cloud of this material is known as the Stromgren Sphere. Areas in which this material abounds can contain Bok Globules. Its presence characterizes the evolution of a GMC to a type of region named for this material, and the Lyman Alpha line is produced when this material recombines with free electrons. This material names the regions such as the Pillars of Creation in the Eagle Nebula in which star formation occurs. For 10 points, name this material that astronomers dub "H two," the charged form of the simplest element.
Franco, Tenorio-Tagle, and Bodenheimer found that the production of this material propagates outward exponentially, and a critical value of three halves characterizes the exponential "w" factor of expansion; for values exceeding the critical value of "w," this material is produced supersonically in the so-called "champagne phase."
{ionized hydrogen} [accept word forms like {hydrogen ion}s; accept {H II} or {H II Region} before read; prompt on {hydrogen}; prompt on {H}; do not accept “H I” or “neutral hydrogen”]