Time, even astronomical time, is made of moments. The universe began in a moment around 13.7 billion years ago. The sun was born in a moment some 4.6 billion years ago, when hydrogen atoms began fusing into helium. At another moment, some 5 billion years from now, the sun will exhaust its fuel and begin a slow death. Somewhere in the Milky Way galaxy, a star like our sun dies roughly every month. When that happens, it briefly exhales an extraordinarily beautiful, complex puff of gas known as a planetary nebula.
At the center of the Red Spider nebula lies a white dwarf that is nearly 1 million degrees Fahrenheit. A wind of fragmented atoms blows off it at millions of miles per hour. This star is a recent corpse: The surrounding gas, fluorescing and whipping into waves, was once the star's atmosphere but was cast off when fusion reactions ...
