How fast is a star?
Though the stars in the sky seem pretty fixed, they're actually all moving relative to each other. You just can't tell because they're so far away. Even the constellations are only temporary — in another 50,000 years, they may look very different!
No two stars are moving the exact same way, either. Some move at very different speeds, which means that while some stars are like this:
Others are like this:
Or something like that, anyway. They're not jumping to light speed, but they are pretty dang fast.
How do you track down a super-fast star?
That's what William Chick and his team of astronomers at the University of Wyoming wanted to do.
"We are using the bow shocks to find massive and/or runaway stars," said Henry Kobulnicky, another astronomer from the University of Wyoming.
Wait. Bow shock? What the heck is a bow shock?
As the stars zoom through space, material shoots out of them, creating a kind of solar wind. This wind hits any dust or gas in the star's way, causing it to pile up in front of the star. It's kind of like how a boat makes water bunch up in front of it.
On a boat, it's a bow wave. On a star or a bullet or a plane, it's bow shock.
Eventually, the bow shocks' big, chaotic pileup heats up the gas and dust in front of the star and causes it to glow. Most of the light is infrared, which means it's invisible to the naked eye. But if you have an infrared telescope, you can spot the bow shocks. Some of them are a bit hard to see:
But some of them are just ... wow.
That star, called Zeta Ophiuchi, is hurtling across the galaxy at 54,000 mph and is gigantic — 20 times as massive as our sun. It's the Rebel Without a Cause of stars — living fast, dying young. It'll speed across the galaxy for about another 4 million years before exploding in a gigantic supernova like some sort of cosmic firework.
What made these stars so fast in the first place?
"Some stars get the boot when their companion star explodes in a supernova," said Chick. That's what they think happened to Zeta Ophiuchi up there. Others get slingshotted out of star clusters.
Our own sun isn't moving quite as fast as Zeta Ophiuchi; it's in the slow and steady camp. As for exactly how fast, it depends on what you're measuring it against, but Stanford University puts the sun's speed at a more stately 45,000 mph. We're not sure if our sun has a bow shock.
To find these stars, Chick and his team used data from a pair of powerful telescopes located in outer space, the Spitzer Space Telescope and Wide-field Infrared Survey Explorer (WISE). Other researchers are also looking at bow shocks to try to learn how these massive, fast stars live and die. Learning more about them could help us understand more about our own solar system and how the universe works.