On June 27, the asteroid 2011 UL21, as wide as a mountain, will fly near Earth at a distance of about 8 million kilometers, making it one of the largest asteroids to pass this close in over a century.
The asteroid 2011 UL21 will approach Earth this weekend at a speed of approximately 93,000 km/h. This potentially hazardous object is among the largest asteroids to come close to Earth in more than 100 years, according to Live Science.
Simulation of the asteroid heading towards Earth. (Image: Sky News).
The orbit of 2011 UL21 occasionally brings it within 1.3 astronomical units (AU) of the Sun, approximately 1.3 times the average distance between Earth and the Sun. It takes 3 years for it to complete one orbit around the Sun. Based on previous observations, 2011 UL21 has a diameter of 1.7 to 3.9 kilometers, making it larger than 99% of known near-Earth asteroids, according to the European Space Agency (ESA).
2011 UL21 is likely at least 10 times smaller than the largest asteroid ever to collide with Earth, the Vredefort asteroid, and 5 times smaller than the asteroid that caused the extinction of the dinosaurs 66 million years ago. However, while the potential impact force from 2011 UL21 is not as severe as those in historical collisions, this asteroid could still cause continent-wide damage and release enough debris into the atmosphere to significantly alter the climate, which is why it is considered a “planetary destroyer.”
On June 27, 2011 UL21 will pass by Earth at a distance of 6.6 million kilometers—the closest it has come in at least 110 years, according to simulations from NASA’s Jet Propulsion Laboratory (JPL). Due to this distance, NASA categorizes it as a potentially hazardous object. However, 2011 UL21 will still be about 17 times farther from Earth than the Moon.
Although 2011 UL21 does not pose a threat to Earth now or in the future, it is one of the 10 largest asteroids to pass within 7.5 million kilometers of Earth since 1900, according to Gianluca Masi, an astrophysicist and director of the Virtual Telescope Project (VTP). 2011 UL21 can be observed in the night sky through telescopes. It will be brightest on June 28-29 and can be seen from the Northern Hemisphere. At its brightest, 2011 UL21 will have a brightness comparable to that of Proxima Centauri, the closest star to the Sun, according to VTP.
2011 UL21 will not come this close to Earth again until 2089, when it will be 2.7 million kilometers away, closer than its current approach by 2.5 times, according to HPL. Researchers have not recorded any hazardous asteroids that could collide with Earth in the next 1,000 years. However, some smaller asteroids will pass very close in the coming years. For instance, the asteroid Apophis, large enough to wipe out a city, will pass near Earth at a much closer distance than satellites in 2029.
