A few weeks ago, astronomers discovered a small asteroid on a course close enough to Earth to cause concern. The discovery was made on April 27, and the closest approach was the day after. The object was small and unlikely to do any damage but nonetheless, researchers tracked it and were able to estimate its orbit with exquisite precision.
The asteroid, known as 2020 HS7, is between 4-8 meters across (13-24 feet) according to the European Space Agency (ESA) and flew 36,400 kilometers (23,000 miles) from Earth’s surface, making it among the 50 closest near-Earth objects (NEOs) ever recorded. This is about the location of what is known as geostationary orbit, where satellites are placed to orbit our planet in 24 hours (so remaining over the same portion of the Earth). Luckily the closest satellite was 1,200 kilometers (745 miles) away at the time.
The asteroid was discovered by NASA’s Panoramic Survey Telescope and Rapid Response System (Pan-STARRS) in Hawaii. After initial detection, less than an hour of observations determined that the risk of hitting Earth was one-in-10. Fifty minutes after the asteroid was first reported, the Xingming Observatory in China released follow-up data on its position, motion, and brightness. Shortly after, ESA alerted the Tautenburg observatory in Germany, which also joined in the effort. Working together, the path of the object quickly became clear.
“Despite posing no threat to Earth, the detection, follow-up, and characterization of this new asteroid was an interesting exercise, testing the discovery and rapid follow-up capabilities of observers worldwide,” ESA stated.
That’s both good news and encouraging to hear. Over the last few years, there have been many discussions about humanity's preparedness against threatening NEOs. Several table-top exercises between international and national agencies have been carried out, mostly focusing on city- and region-destroying-sized space rocks (both the French Riviera and New York City have been among the unfortunate targets in these simulations), but smaller asteroids could still be dangerous.
The Chelyabinsk meteor that fell in Russia in 2013 is a good example of that. Fortunately, no one died, but the shockwave produced by that event shattered glass and damaged buildings for miles, causing around 1,500 hospitalizations.
A crucial improvement has been the increase in the monitoring of these objects. At the start of 2019, about 19,300 near-Earth objects were detected. Now the number has increased by one-fifth, nearing 22,800, with more asteroids discovered every single week.
Of these, 110 are comets while the rest are asteroids. Many of these objects, while sharing space with our planet, never get close enough to be dangerous. Only 2,082 are deemed potentially hazardous and of those, only 156 are above 1 kilometer in size. If such an object were to hit, it would cause devastation on a global scale, but none of these are currently on a collision course with Earth.