Figure 12-5Formation of a Bipolar Planetary Nebula Bipolar planetary nebulae may form in two steps. Astronomers hypothesize that (a) first, a doughnut-shaped cloud of gas and dust is emitted from the star’s equator, (b) followed by outflow that is channeled by the original gas to squirt out perpendicularly to the plane of the doughnut. (c) The Hourglass Nebula appears to be a “textbook” example of such a system. The bright ring is believed to be the doughnut-shaped region of gas lit by energy from the planetary nebula. The Hourglass is located about 8000 ly (2500 pc) from Earth.