Jupiter might be a lot more than just another big body in our solar system — the massive gas giant could very well be Earth's protector. Early Monday morning, amateur astronomers captured a brief but bright flash of light on the planet's surface, which scientists now believe was the result of a massive asteroid that could've been headed our way. (See a video below.) Here's what you need to know:

What did stargazers see, exactly?
Something mysterious smashed into Jupiter's surface on Monday, resulting in a 100-mile-wide fireball that was large enough to glimpse from a backyard telescope on Earth, more than 454 million miles away. "It was a bright flash that lasted only 1.5 to 2 seconds," said Dan Peterson, the amateur astronomer from Racine, Wis., who first reported the "impact flash" in a post on CloudyNights.com. Scientists think Jupiter may have even "saved Earth from a devastating cosmic collision," says Robert T. Gonzalez at io9.

Was the asteroid really going to hit Earth?
That's hardly certain. But at the very least, this impact event suggests that the "giant planet has taken another bullet for the solar system team," says Alan Boyle at NBC News. This is the third time since 2009 that observers have seen an impact flash on Jupiter's surface, and some astronomers think the big planet's gravitational pull serves as a sort of "cosmic shield" for the inner rings of planets — including Earth — "sweeping up incoming objects that would have a deadlier effect" if they were to crash into us. 

Why do scientists think Jupiter is a "cosmic shield"?
It used to be believed that impacts on Jupiter's surface were "rare cosmic events," says Andrew Fazekas at National Geographic. But new evidence suggests that cataclysmic crashes are actually "fairly common," including the 1994 impact when the comet Shoemaker-Levy 9 met its doom on the planet's surface, resulting in a "spectacular explosion." A few scientists think that without Jupiter's protection, life on Earth wouldn't have been able to develop.

What's next?
Astronomers will try to figure out what caused this week's giant explosion. To do so, they'll observe Jupiter's cloud tops over the flash zone, which work as a sort of cosmic "signature" in the aftermath of impacts. If it was indeed a comet or asteroid, the atmosphere will overheat and produce soot-like debris. Only then will NASA astronomers step in for closer inspection. "Professional telescopes and Hubble are typically very oversubscribed," says NASA's Amy Simon Miller, "and won't be called into action unless a debris field is confirmed first by amateurs."

Sources: io9National GeographicNBC NewsSpace.com