Near-Earth asteroid 2021 GW4 exceptionally close encounter: an image – 12 Apr. 2021

In about four hours, the near-Earth asteroid 2021 GW4 will safely come exceptionally close, reaching a minimum distance from Earth’s surface of about 20.000 km (geostationary satellites are at 36.000 km), that is 5% of the average lunar distance. We spotted it earlier today, here it is our image.

Near-Earth asteroid 2021 GW4. 12 Apr. 2021.

Near-Earth asteroid 2021 GW4. 12 Apr. 2021.

The image above comes from a single, 180-second exposure, remotely taken with the “Elena” (PlaneWave 17″+Paramount ME+SBIG STL-6303E) robotic unit available at Virtual Telescope. The telescope tracked the fast apparent motion of the asteroid, this is why stars show as long trails, while the asteroid looks like a bright and sharp dot of light in the center of the image, marked by an arrow. Sky was heavily cloudy, we were lucky to capture a good image.

At the imaging time, asteroid 2021 QW4 was at about 300.000 km from the Earth (average lunar distance: 384.400 km) and approaching us. It was discovered by the Mt. Lemmon survey on 8 Apr. 2021 and announced the following day.

Geostationary satellites are placed at 36.000 km above the Earth surface, so 2021 GW4 is coming significantly closer. We repeat this is an absolutely safe close approach. Asteroids of that size coming so close are relatively rare, but so far this year we had four objects coming within 0.07 lunar distance from Earth’s center: 2021 GW4 is the largest of these four rocks. So far it wins the 2021 bronze medal as for the minimum distance in absolute. In the recent past, objects of this size impacted with our planet, too: 2008 TC3, 2014 AA, 2018 LA and 2019 MO. They can produce an air burst and occasionally, fragments can reach soil (as in the case of 2008 TC3 above Sudan). Of course, we also had the Chelyabinsk event in 2013, which was much larger (20 meters) than 2021 GW4.

This 3.5 – 7.7 meters large asteroid will reach its minimum distance (about 20.000 km) from us on 12 Apr., at 13:01 UTC (source: Nasa/JPL). Of course, there were no risks at all for our planet.

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