On the morning of Thursday, July 25, 2019, an asteroid about the size of a motor home whizzed past the earth at around 50kms per second. At its closest, ”Asteroid 2019 OK” was only 70,000 kms from our atmosphere, or less than half the distance to the moon. Although this wasn’t exactly an extinction-sized asteroid, the scariest part wasn’t it’s size, rather, it was the fact that astronomers were completely unaware of the potential threat until only hours before the fly-by. This was largely due to the fact that it came from the direction of our sun, which made it almost impossible to see. Luckily, it did not hit us, and we can all go back to our Snapchats and Instagrams because there’s no chance that could happen twice in one lifetime …right?
Was that a rare occurrence? Just how often do these “close calls” happen? And how bad could it be if one does actually hit? Afterall, the asteroid that killed the dinosaurs, during the Chicxulub event 65 million years ago, was estimated to be anywhere between 30-150km wide — thousands of times bigger than our recent passer-by. But even the smaller asteroids can be devastating. Asteroid 2019 OK belongs to a class of asteroids dubbed by astronomers as “city killers” because…well…that should be an easy one to figure out. And as to how frequently this can happen, that might be surprising.
The Taurid Meteor Stream
The Taurid meteor stream is a giant ring of comets and meteors about 30 million km wide, with an orbit about 3 times larger than that of the earth. It gets its name from the fact that when observing the meteor showers from Earth, they appear to be emanating from the constellation of Taurus, although that is just an optical illusion. Due to the unique nature of the Taurid’s orbital path, we pass through the stream twice per year: once from early June to late July (sometimes called the “Beta Taurids”, they peak around July 10, but are very hard to see because they happen on the daytime side of our planet), then again from early September to early December (peaks on October 10 in the Northern Hemisphere and November 12 in the Southern Hemisphere).
There are several large objects that make up the Taurids, including comet Encke, which is about 5 km wide. Some experts say there are about 19 large fragments still remaining from a much larger object that was about 100-200 km in diameter when it broke apart millions of years ago, most likely due to tidal forces exerted on it while passing the sun. In fact, astronomers have identified and catalogued over 200 asteroids with a diameter of 1km or more. Conservative estimates suggest that for every asteroid or comet we see, there could be thousands more that remain undetected. Every once in a while, we get a reminder of just how dangerous those undetected objects can be.
The Occasional Visitor
On July 30, 1908, a meteor estimated to be 60-100 metres in diameter, entered our atmosphere over a remote section of the Eastern Siberian Taiga, and exploded in mid-air with a force 1000 times greater than that of the nuclear bomb dropped on Hiroshima at the end of WWII. In what became known as the Tunguska Event, 2000 square km of forest were flattened instantly, and the shock wave shattered windows over 100 km away. Fortunately, because this happened over such a remote part of Siberia, there were no serious injuries. Had this occurred over a heavily populated city, the death toll would be unimaginable. Another similar event, dubbed the Chelyabinsk Meteor Event, which took place in 2013, was captured on hundreds of dashboard cameras and security systems throughout Russia, offering a rare glimpse at the immense power possessed by these celestial fire-bombs.
Evidence has also been mounting up, suggesting that yet another asteroid originating from the Taurids was responsible for a catastrophic period of intense global climate change known as the Younger Dryas, which took place roughly from 12,800-11,600 years ago, which many scientists now say is the likely cause of the mass-extinction event that wiped out the Clovis culture, a population of early humans, and nearly all of the megafauna (large mammals such as sabre-tooth tigers and mammoths) that once inhabited North America.
Although these events could be considered “rare” relative to a human life-span, relative to the age of the earth, I’d say it’s safe to expect these events to occur on a semi-regular basis. Additionally, there are other meteor streams, besides the Taurids, such as the one formed by Halley’s Comet, along with countless rogue asteroids and other space debris completely unknown to astronomers that could potentially be on a collision course with our planet right now, and we would never know until it is too late. Even if we could detect an asteroid or comet on it’s way to destroy our planet, there isn’t much we could do to stop it, aside from very Armageddon-like techniques that are far from figured out.
It can be quite humbling to sit back and try and take all that in. Just understanding how small we really are in the context of the universe, can be — relieving, in some strange way. A certain “problem-free philosophy” comes to mind.
It means no worries. Might as well live your life everyday as if it could be destroyed tomorrow. It really doesn’t matter what celebrity is wearing what shoes, or who is running the oval office, when 80 percent of life on the planet is wiped out.