The NASA logo is displayed at the agency's booth during...

The NASA logo is displayed at the agency's booth during CES 2018 at the Las Vegas Convention Center on Jan. 11, 2018. Credit: Ethan Miller

‘Close” is a relative word.

In real life, close is the house next door, the car riding your bumper, a fastball under your chin.

In astronomy, close is 45,000 miles. That’s how close an asteroid known as 2019 OK came to Earth recently as it swiftly passed by.

One astronomer called it “uncomfortably close.”

But the fact that it just missed us, in cosmic terms, isn’t the point. It’s that NASA, and astronomers the world over, missed its approach.

Many said they were stunned. They said it came out of nowhere. No one was tracking it. They didn’t realize Asteroid 2019 OK was in the vicinity until just before it zipped past.

This particular space rock isn’t small, somewhere between 187 and 427 feet across. An asteroid some 6 miles wide killed off the dinosaurs. Though, for perspective, we should note that astronomers call an asteroid like 2019 OK a “city-killer,” because, well, you get the idea.

It was traveling 24 kilometers per second, which might not instantly impress until you do the math and discover that’s nearly 54,000 mph. Put it all together and, as one astronomer told The Washington Post, Asteroid 2019 OK would have hit Earth like a nuclear weapon, with a force in the “ballpark” of 10 megatons of TNT. That’s 22 billion pounds of TNT.

Readers of this space know that I’m a space geek. What I like most about Asteroid 2019 OK is that it reminds us how much we have yet to learn, how much of space is unknown, and how despite our vast technological achievements there are things we humans can’t do a darn thing about right now. If that sounds sobering, it is. It’s also useful; hubris rarely is productive.

To that end, Congress has ordered NASA to find 90 percent of the large asteroids (459 feet or more) that pose a threat to Earth by 2020. NASA won’t pull that off — it has located less than half of the estimated 25,000 — but it has found 90 percent of the ones that are at least 3,281 feet across.

Asteroid-hunting, as it turns out, is tricky business. No matter your equipment or method, the asteroid has to be close enough to spot, and you have to be looking in the right direction. That’s true about many threats on Earth, too, when you think about it.

NASA also is looking at some cool ways to deflect or destroy threatening space rocks. It’s a noble mission. We should want to know what’s out there, and whether we can deal with it. Like the meteor that broke up over Russia in 2013, unleashing a massive shock wave that broke windows, collapsed roofs and injured 1,200 people. It was 65 feet across, a comparative baby. Or like the last OK 2019-size asteroid to hit Earth, in 1908 in Siberia. The explosion leveled 770 square miles of forest — 80 million trees flattened — in what is now known as the Tunguska event.

By comparison, 2019 OK wasn’t exactly a freakout moment, although Alan Duffy, the lead astronomer at the Royal Institution of Australia, told The Washington Post that what remains unknown “should worry us all, frankly. It’s not a Hollywood movie. It is a clear and present danger.”

We all can rest easy that the odds are stacked high against a city-killer asteroid landing where we live. But when one lands on Earth, it has to land somewhere, and whoever it lands on won’t be around afterward to calculate the odds of getting hit.

The Jet Propulsion Laboratory at the California Institute of Technology has a neat website that lists all upcoming close approaches. There are six more this month, beginning with one on Saturday.

Those are the known approaches, of course.

As for the unknown ones, well, you know what they say:

What you don’t know could, in fact, hurt you.

 Michael Dobie is a member of Newsday’s editorial board.


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