An important contributor to the spectral lines of these objects is collisional excitations.
An important contributor to the spectral lines of these objects is collisional excitations. These objects are often found in conjunction with Wolf-Rayet stars and can, in that case, take on the shape of a pinwheel. One subtype of these objects, sometimes called Strömgren spheres and usually found with young O- and B-type stars, has characteristic emission lines of ionized hydrogen. That subtype is H II regions, and another subtype is their planetary type. The creation of one of these objects was observed by Chinese astronomers in 1054, after a supernova in Taurus. For 10 points, name these interstellar clouds of gas and dust exemplified by the Crab.
An important contributor to the spectral lines of these objects is collisional excitations.
emission nebulae [or planetary nebulas; or H II regions until is read]