Messier 54 (also known as M54 or NGC 6715) is a globular cluster in the constellation Sagittarius. It is about 87,000 light-years, translating into a true radius of 150 light-years across. It is one of the denser of the globulars.
Lightning Spectra... taken during a thunderstorm over Paris, the forking lightning bolt heats surrounding air to between 36,000 and 54,000 degrees Fahrenheit, breaking apart air molecules into ionized plasma. The bright lines of the spectra reveals the presence of nitrogen and hydrogen in our atmosphere.