Knowing that there are individuals who are physically employed to observe the night sky gives us some comfort in the knowledge that we will at least be told if an asteroid will strike the Earth.
The possibility of a planet-killer-sized asteroid appearing out of thin air, as is so frequently depicted in contemporary media, is exceedingly implausible since technology and near-Earth surveys have improved to the point where it is quite unlikely.
Even smaller ones that would merely destroy a city or a portion of a continent receive enough attention to determine whether or not they represent a threat.
And the ESA is pleased to report that one of the most dangerous asteroids was successfully removed from their list of probable impacts in anticipation of Asteroid Day 2022, which took place on June 30.
The asteroid, 2021 QM1, was discovered for the first time on August 28, 2021, at the Mount Lemmon observatory. It was one among perhaps a dozen near-Earth asteroids found that night, and at first there was little cause for concern. However, further observations indicate that it may pass Earth quite close around 2052.
2021 QM1, which has a diameter of roughly 50 meters (160 feet), would have the power to explode at a height of about 9 kilometers, releasing the equivalent of over six megatons of TNT into the atmosphere (6 miles). It is 400 times stronger than the Hiroshima nuclear explosion, the most widely used measure of high energy effects.
An asteroid of such size has only ever struck Earth once in recent memory. The Tunguska, which produced a massive 12 megatons of energy and whose date the Annual Asteroid Day commemorates, fortunately occurred over a distant area of Siberia.
So, even though it destroyed 2150 square kilometers (830 square miles) of forest, only three individuals are believed to have perished as a result of the incident. But if such an impact occurred over a densely populated area, the outcome may be disastrous.
When gathering further information about 2021 QM1, asteroid defenders were undoubtedly thinking about that incident.
Unfortunately, they would experience a brief period of anxiety due to another astronomical occurrence. For a few months, the asteroid vanished behind the Sun, preventing future observations.
Since most scientists believe that patience is a virtue, they patiently waited and prepared to gather more data using the Very Large Telescope, one of their greatest tools for locating asteroids.
They were prepared as the asteroid emerged from the sun's shadow. They also succeeded in taking a picture of the asteroid that is the faintest ever seen.
They were able to conclude from that observation that there is no possibility that 2021 QM1 will strike Earth in 2052 as originally projected. In the near future, its orbital route won't pose any dangers.
The asteroid 2021 QM1 is not the first to be taken off the hazardous list as a result of a less-than-ideal blocking maneuver by another celestial body.
Following observations were obstructed by the moon in February, the ESA took another asteroid off the list. The known asteroid AE1 had a far more immediate probable impact window at the time, 2022—4 July 2023.
The 70 m rock could have been the most catastrophic fireworks show ever, perhaps causing even more damage than the 2021 QM1 explosion.
All of this raises the issue of what we would actually do in the event that another asteroid with a possible impact event is discovered. The teams of asteroid defenders will continue to maintain a watchful eye, although there are several preparations in place that are best addressed in other pages.
Furthermore, there is nothing to worry about at the moment.
