Two asteroids are set to pass near our planet this week – one big enough to destroy a city and the other big enough to end civilization.
Don’t panic.
Both have zero probability of impacting Earth. And depending on where you are in the world, you might even see one of them.
The larger of the pair, (415029) 2011 UL21, will fly by Thursday at 4:14 PM ET at a distance more than 17 times farther than the Moon. It is a whopping 7,600 feet long, but without powerful binoculars it will be too far away to be seen easily.
However, two days later, a smaller space rock named 2024 MK will come significantly closer to humanity. At 9:46 a.m. ET on Saturday, it will fly past Earth at 75 percent of its distance to the moon. If you have a decent pair of binoculars in your backyard, or even some good binoculars, and your sky is clear of clouds, you can see the 400- to 850-foot rock as a speck of light flashing across the starry sky before sunrise. .
“The object will be moving fast, so you have to have certain skills to see it,” said Juan Luis Cano, a member of the European Space Agency’s Planetary Defense Office.
Astronomers in the United States, especially those farther southwest, may catch an asteroid passing by the planet. Those atop Hawaii’s Mauna Kea volcano will be in a good position to see it as the asteroid approaches before sunrise. But people in South America may have the easiest viewing experience, said Andrew Rivkin, a planetary astronomer at the Johns Hopkins University Applied Physics Laboratory.
Small asteroids and comet fragments occasionally pierce Earth’s atmosphere to create a harmless light show. Much more rocky and icy debris simply misses the planet and often gets squeezed between the Earth and the Moon.
A 2024 MK asteroid strung on this celestial needle is less common. “Things this big are rare this close, but they happen on a 10-year timescale – it will be the third (that we know of) this century,” said Dr. Rivkin in an email.
Anyone who doesn’t score 2024 MK doesn’t have to feel left out for too long. On April 13, 2029, Apophis, an 1,100-foot-long asteroid, will fly by less than 20,000 miles above Earth’s surface, closer than the orbits of geosynchronous satellites — meaning it will be visible to the naked eye.
Such close approaches are useful for planetary defense researchers. This week’s asteroids will be tracked by radar arrays on Earth, making it possible to accurately determine their dimensions and further paths.
“These measurements will greatly reduce the uncertainties in their motion and allow us to calculate their trajectories further into the future,” said Lance Benner, principal investigator of the Asteroid Radar Research Program at NASA’s Jet Propulsion Laboratory.
The double flyby also serves as a coincidental showcase for Asteroid Day on June 30, a United Nations-backed occasion to raise awareness of asteroid impacts.
On that day in 1908, a roughly 160-foot-diameter space rock exploded over a remote belt of Siberia, instantly leveling 800 square miles of forest—about the area of ​​the Washington, DC metro area. It is known as the Tunguska Event after the river flowing through the area it destroyed.
Although more are being discovered every year, most near-Earth asteroids capable of destroying a city have yet to be found. Fortunately, much more can be seen with a pair of telescopes under construction—the Vera C. Rubin Multipurpose Observatory in Chile and NASA’s Near-Earth Object Surveyor spacecraft.
Asteroid 2024 MK is at least twice as long as the Tunguska impactor. It is certainly welcome that the asteroid has been found before its encounter with Earth and that it will miss us. But astronomers discovered the space rock on June 16.
“The 2024 MK case is another reminder of the fact that there are still plenty of large objects to be found,” said Dr. Cano. Space agencies have plans and technology to defend the planet from killer asteroids—but only if they find them before the asteroids find us.