On Sunday, an asteroid flew 2,950 km from the Earth’s surface. In fact, no one had noticed her before.
So what is not in this sensational title? First of all, information about the size of the asteroid. However, reports speak of an object the size of a passenger car, so we can assume that the object was 2 to 6 meters in diameter. With such dimensions, it is difficult to really determine whether we are talking about an asteroid or a meteoroid.
An asteroid or a meteoroid?
Traditionally, the division between the two categories was placed where the possibilities of detecting such objects with a telescope ended. If an object was visible in the telescope, it was an asteroid, if not, it was already a meteoroid. With the development of technology, the border moved towards smaller and smaller objects.
In 1995, the border was set at the level of 10 m. At such borders, the rock that visited us on Sunday was only a meteoroid. But we are in 2020 and, for example, in 2015, we managed to see an object with a diameter of 2 m using the Infrared Telescope Facility. In this case, we can freely call the object from Sunday an asteroid.
Record short distance detected flight
It’s actually a record. Never before has it been possible to record such a close pass that would not end up entering the Earth’s atmosphere. This time, however, the asteroid passed near the Earth and continued on. In the near-flight catalog at the Sormano Astronomical Observatory in Italy, this is the closest flight of all recorded so far.
This does not mean, of course, that there are no such flights. There are probably quite a few of them, but at such a distance they are extremely short and if a given section of the sky is not monitored by anyone, no one will even notice such a passage.
The asteroid attacks unexpectedly
The asteroid discovered on Sunday posed no threat to people. If it entered the Earth’s atmosphere, it is quite possible that it would have burned during the flyby and no debris would have reached the Earth’s surface. For comparison, the object that entered the Earth’s atmosphere above Chelyabinsk and did a lot of damage on Earth had a diameter of 17-23 meters, and the asteroid that ended the era of dinosaurs had a diameter of several kilometers.
Astronomers, however, are concerned about something completely different – the fact that no one has noticed this asteroid before. If it were a larger object, we wouldn’t even know it was approaching us.
One of the reasons for this is the fact that the asteroid came to us from the Sun, so the observatories were not able to see it against the background of the night sky, illuminated by the Sun. On the contrary, this object was in the sky during the day, when sunlight prevents the discovery of objects heading towards us from the center of the solar system.
We are helpless when it comes to detecting asteroids heading towards us from the sun, because asteroids can only be detected with optical telescopes (such as ZTF) and we can only search for them in the night sky, says Paul Chodas, director of the Near Earth Research Center at NASA.
The 2020QG asteroid was first noticed with the Palomar Observatory’s telescope only six hours after it was fully close to Earth, after it had passed and farther away from our planet.
Despite many telescopes directed constantly at the sky, objects appear from time to time that we only notice after they fly past the Earth. Sunday’s flight, however, was the closest to Earth of all those so far observed.
The newly discovered asteroid ZTF0DxQ flew 1/4 the diameter of the Earth, thus becoming the closest known pass that did not end in an impact with Earth, wrote Tony Dunn, author of orbitsimulator.com.