The Universe 03

Stars

Scattered among the stars of the Milky Way are supernova remnants, each one the remains of a colossal stellar explosion. These filaments of glowing gas are the outer layers of a star which has recently destroyed itself. The gas is unraveling returning star-stuff back into space. And at its heart are the remains of the original star: a dense, shrunken stellar fragment called a pulsar. A natural lighthouse, blinking and hissing. A sun that spins twice each second. Pulsars keep such perfect time that the first one discovered was thought to be a sign of extraterrestrial intelligence. Perhaps a navigational beacon for great ships that travel across the light years and between the stars. There may be such intelligences and such starships, but pulsars are not their signature. Instead, they are the doleful reminders that nothing lasts forever; that stars also die.

We continue to plummet, falling thousands of light years towards the plane of the galaxy. This is the Milky Way, our galaxy, seen edge-on: billions of nuclear furnaces converting matter into starlight. Some stars are flimsy as a soap bubble. Others are a hundred trillion times denser than lead. The hottest stars are destined to die young. But red giants are mostly elderly. Such stars are unlikely to have inhabited planets. But yellow dwarf stars, like the sun, are middle-aged and they are far more common. These stars may have planetary systems. And on such planets, for the first time on our cosmic voyage, we encounter rare forms of matter: ice and rock, air and liquid water.

Close to this yellow star is a small, warm, cloudy world with continents and oceans. These conditions permit an even more precious form of matter to arise: life. But this is not the Earth. Intelligent beings have evolved and reworked this planetary surface in a massive engineering enterprise. In the Milky Way galaxy, there may be many worlds on which matter has grown to consciousness. I wonder, are they very different from us? What do they look like? What are their politics, technology, music, religion? Or do they have patterns of culture we can’t begin to imagine? Are they also a danger to themselves?

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