Our Sun is actually a cosmic refugee. Around 4.6 billion years ago, it first ignited in a hostile, radiation-blasted neighborhood 10,000 light-years closer to the Milky Way’s center than it is now.

Isaac Asimov described the solar system as the sun, Jupiter, and debris. He wasn't wrong—the sun is 99.8 percent of the mass of the solar system. But what is that giant ball of fire in the sky? How ...