Call it a close shave of a celestial sort.
On April 19, an asteroid roughly the size of the Rock of Gibraltar will speed safely by Earth at a distance of 1.1 million miles — or less than five times the distance from Earth to the moon.
NASA says there's no chance the 2,000-foot-wide space rock will hit our planet. But the flyby — remarkably close by astronomical standards — serves as a reminder that somewhere out there an asteroid may have our name on it.
"The odds of an impact for asteroids are very low on 'human timescales' (a hundred years are so)," Dr. Amy Mainzer, an astronomer at the Jet Propulsion Laboratory in Pasadena, Calif., told NBC MACH in an email. "However, because the consequences could potentially be severe, it's not something we should completely ignore."
Severe may be an understatement. If an asteroid like this one were to strike Earth, it might blast an impact crater about 10 kilometers wide, Dr. William F. Bottke, a planetary scientist and asteroid expert at the Southwest Research Institute in Boulder, Colo., told MACH in an email.
Watch: Flyby path of the asteroid
What do we know about this asteroid, which is formally called 2014 JO25? Not much beyond its trajectory and the fact that its surface is about twice as reflective as the moon's. The asteroid will be so close and so bright that, with nothing more than a small telescope, it may be visible in the night sky for a day or two.
The asteroid hasn't come this close for at least the last 400 years and won't come this close again for at least the next 500 years.
Smaller asteroids pass within this distance from Earth several times a week, NASA says. But approaches this close by an object this big occur only once a decade or so, according to Mainzer. The last time such a sizable asteroid came this close was in 2004. The next time will happen in 2027, when a half-mile-wide asteroid known as 1999 AN10 will fly by the Earth at a distance of about 236,000 miles.
Mainzer said scientists had found more than 95 percent of asteroids big enough to affect Earth on a global scale if they were to strike our planet. But about 75 percent of objects big enough to cause severe regional damage remain undiscovered.
What if we were to discover a big asteroid on a collision course with Earth? As long as we have a couple of decades notice, NASA says, we might be able to deflect it by blasting it with a "kinetic impactor" or positioning a large mass nearby to serve as a "gravity tractor."
But don't worry too much. NASA says it knows of no asteroid that poses a significant risk of impact with Earth over the next century.