An asteroid just flew by Earth about 50% the distance to the moon, and we barely saw it coming

Near earth object asteroids neos nasa m15 091bNASAAn illustration of a near-Earth object, or NEO, passing by Earth.

On Monday, while people on the US East Coast were making coffee, dropping kids off at school, and cursing in traffic, a space rock as big as a 10-storey building slipped past Earth.

The asteroid, dubbed 2017 AG13, was discovered on Saturday by the University of Arizona’s Catalina Sky Survey, according to an email from Slooh, a company that broadcasts live views of space.

It’s between 50 and 111 feet (15 to 34 meters) long, and when it swung by Earth, 2017 AG13 was moving at 9.9 miles per second (16 kilometers per second). The near-Earth object, or NEO, came within about half the distance between the moon and Earth, according to Slooh.

“This is moving very quickly, very nearby to us,” Eric Edelman, an astronomer with Slooh, said during a live broadcast of the flyby at 7:47 a.m. ET on January 9. “It actually crosses the orbits of two planets, Venus and Earth.”

A near miss

Russian meteor chelyabinsk trailFlickr/Alex AlishevskikhThe trail of the asteroid that exploded over Chelyabinsk, Russia, on February 15, 2013.

What would have happened if the asteroid had plowed into our atmosphere?

According to an asteroid-impact simulator called “Impact Earth!” by Purdue University, not as bad as it might sound.

Had a porous rock asteroid 111 feet long hit Earth at a 45-degree angle, one simulation showed, it would have exploded as an air burst. The blast would have released about 700 kilotons’ worth of energy — dozens of times as powerful as the atomic bomb detonated over Hiroshima.

But since it would have occurred from a distance of about 10 miles from the Earth’s surface, it probably wouldn’t have had much effect on the ground; if anything, a high-altitude boom may have sounded as loud as heavy traffic.

Such strikes occur about once every 150 years, according to Purdue’s simulator.

However, according to Slooh, 2017 AG13 was “roughly the same size as the asteroid that struck Chelyabinsk, Russia, in 2013,” so the on-the-ground effects — including shattered windows and slightly damaged buildings — may have been similar.

“It is not that uncommon of an event, which is one of the reasons it is interesting,” Mark Sykes, director and CEO of the Planetary Science Institute, told Business Insider in an email.

In fact, about 38 more “close approaches” of asteroids like 2017 AG13’s are expected in January alone, according to NASA’s Near Earth Object Program.

Hunting for NEOs

Neocam asteroid hunter spacecraft discovery nasa jpl caltechNASA/JPL-CaltechAn artist’s concept of the NEOCam asteroid-hunting mission.

Sykes is one of the scientists behind a proposed asteroid-hunting space telescope called the Near-Earth Objects Camera, or NEOCam.

“NEOCam would detect some of these small asteroids, but because they are small they would have to be closer to be seen,” Sykes said.

The NEOCam telescope is designed to detect larger (yet still relatively small) space rocks of roughly 460 feet or greater. If NEOCam ever launches, a 10-year-long mission would be expected to discover 10 times as many known NEOs of that size or bigger in any previous survey of the sky.

Such objects pose a dire risk to humanity since they can release many times as much energy as a thermonuclear bomb if they strike our planet  — and yet we’re mostly blind to them as Earth drifts through a shooting gallery.

Yet last week, NASA chose for the second time not to fully fund NEOCam.

The space agency instead chose two other missions for future launch: Lucy, which will explore swarms of asteroids in Jupiter’s orbit, and Psyche, which will fly out to and investigate the giant metallic core of a dead protoplanet.

While NASA said it intends to give NEOCam partial funding for another year, the space agency couldn’t tell Business Insider how much or under what conditions, nor what its long-term plans are for the mission.

So for now, NEOCam’s future — and our ability to find these unseen threats — remains uncertain.

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