Weird Object: SDSS J090745.0+024507

No. 29: The First Star That Got Away

By Bob Berman | Published: Friday, June 12, 2015

RELATED TOPICS: WEIRDEST OBJECTS | STARS

SPEED STAR. A young blue star flies out from its binary system after the galaxy’s supermassive black hole flung it. This star now moves fast enough to actually escape the Milky Way’s gravity.

Astronomy: Roen Kelly

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 (618 km) 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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