747-sized asteroid skimmed by Earth, and scientists didn't see it coming

• Author: AARON REICH
• Published date: 23 September 2021
• Publication title: Jerusalem Post, The: Web Edition Articles (Israel)

Dubbed 2021 SG, according to the NASA-backed International Astronomical Union's Minor Planet Center, the asteroid has a diameter of anywhere between 42-94 meters, with an average diameter of 68 meters, which is around the wingspan of a 747, the height of the Cinderella Castle in Disney World and around half the size of the Great Pyramid of Giza.

The asteroid flew past the Earth on September 16, as noted by asteroid tracker EarthSky. However, scientists only detected it the next day.

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This may seem surprising, given how many asteroids are routinely detected by astronomers and space agencies all over the world. However, this asteroid came from a relative blind spot: the direction of the Sun.

Most asteroids detected by agencies like NASA come at Earth from the "front," meaning they come from the direction facing into the interior of the solar system, coming towards the Earth and the Sun.

But there are asteroids that come from the "back," heading towards Earth from the direction of the Sun and heading outwards.

It is therefore very difficult to see these objects as they approach Earth, especially as they often tend to approach during the daytime when visibility is low due to the Sun's glare.

Generally, the best time to spot these objects is during twilight. This is the case for all objects in space between the Earth and the Sun, such as the planets Mercury and Venus.

According to EarthSky, the asteroid passed by at a very close distance, around half the distance between the Earth and the Moon. It was closest to the planet at around 4:28 p.m. EST, passing by Greenland and Canada. This was a very close call, as most asteroids that pass by the planet do so much farther away.

And while it may seem like a freak, isolated incident, that might not be the case.

On September 7, astronomers in Arizona detected an asteroid, now designated 2021 RS2, coming from the direction of the Sun just hours before it was set to pass by the planet, as noted by EarthSky. Though it was small, around 3.5 meters, it came just 15,340 km. away from the planet's surface.

This is the closest an asteroid has come to hitting the planet in all of 2021, though if it did hit, it likely wouldn't have done a lot of damage, if any.

But the same cannot be said for 2021 SG. With its large size and clocking in at 85,748 km/h (around 23.8 km. per second), the asteroid...