Supernova Remnant Example Spectra

This two-panel figure shows HUT spectra of two different gaseous filaments in the Cygnus Loop supernova remnant. (Click here for a picture of a portion of the Cygnus Loop.) The Cygnus Loop is the leftover, expanding remnant of a stellar explosion that occurred roughly 20,000 years ago some 2000 light years away from earth. As the blast wave expands, it encounters "clouds" of interstellar gas. These clouds get heated by the blast wave, and then cool down by emitting optical and ultraviolet radiation we can see with telescopes.

The upward "spikes" in the figures are called emission lines, and arise from different chemical elements in the gas, such as carbon, nitrogen, oxygen, and helium. The lines are marked with element abbreviations. (Roman numerals indicate the "ionization stage" of the element.) The two spectra from the same object show many differences that are related to the time since the emitting material was first struck by the blast wave. (Figure adapted from W. P. Blair et al. 1991, ApJ, 379, L33, and K. S. Long et al. 1992, ApJ, 400, 214.)

[Note: lines marked with an earth symbol (a circle with a "+" sign) are due to residual atmospheric emissions still present in low earth orbit.]