Can we get out of here? That’s the question pondered for centuries. How do we permanently leave Earth? A cannonball fired upward always returned. With a greater explosive charge and a higher speed, a shell went farther. It wasn’t hard to figure out what speed an object would need to fall around Earth’s curve and leave our planet permanently. It is 6.96 miles (11.2 kilometers) per second. This is Earth’s escape velocity.

Sounds like a simple concept, and it is. Every celestial object’s mass determines how strongly it glues to itself any nearby planets, moons, or other stars. For the Sun, the escape velocity is a whopping 384 miles (618km) per second if you start out just above its surface. But by the time an object has managed to flee from the Sun to arrive here at Earth’s distance, the escape speed has fallen off to just 26 miles (42km) per second. That’s still faster than our best rockets, which can go only 10 miles (16km) per second. Thus, it’s easier to escape our world than to fight our way outward and wrench free from the Sun’s more insistent grasp.

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Our Milky Way Galaxy, composed of at least 200 billion suns, has its own escape velocity, and it’s nothing trivial. For anything to leave, it needs to travel more than 180 miles (300km) per second. Not surprisingly, no star in our galaxy had ever been found to possess such a speed. Put another way, the immense, beautiful azure spirals and golden nucleus of our Milky Way constitute an integrated unit where all components are attached forever.

Forever, that is, until 2005. That’s when astronomers found the first runaway.

As early as 1988, astronomer Jack G. Hills of Los Alamos National Laboratory in New Mexico had discovered a mathematically possible way for a star to escape the galaxy. If it was a member of a binary star system, and if it passed a precise distance from the supermassive black hole in our galaxy’s center, it could set in motion an intriguing high-stakes pinball game. The black hole could, in theory, yank one member of the binary system in such a way that the other member gets flung off at incredible speed — fast enough to permanently break away from the galaxy.

It could happen. But has it? In 2003, astronomers starting searching for such objects — and reported one only two years later. Astronomers Warren Brown, Margaret Geller, Scott Kenyon, and Michael Kurtz discovered it using the enormous 6.5-meter telescope at the MMT Observatory just south of Tucson, Arizona. It’s a dazzling blue star of spectral type O, with the kind of high metal content expected of stars born in the galaxy’s core. Except that this star is nowhere near there. Instead, it’s whizzing through the constellation Hydra the Sea Serpent in the Milky Way’s suburbs at 433 miles (697km) per second — more than twice the speed necessary to permanently leave the galaxy behind.