This week, two asteroids, one big enough to destroy a city and the other so big it could destroy civilization, will fly near our planet.
Do not panic.
Both have a zero percent chance of the impact on the earth. And, depending on where you are in the world, you might even see one.
The larger of the pair, (415029) 2011 UL21, will pass more than 17 times farther away than the moon at 4:14 p.m. Eastern Time on Thursday. It will be a whopping 7,600 feet long, but will be too far away to easily see without a powerful telescope.
Two days later, however, the smaller space rock, called 2024 MK, will come considerably closer to humanity. On Saturday at 9:46 a.m. Eastern Time, it will zoom past Earth at 75 percent of the moon’s distance. If you’re a decent backyard telescope or maybe even with it a good pair of binocularsand your sky is cloudless, you could see the 120 to 240 meter high rock as a point of light flashing across the starry sky before the sun rises.
“The object will be moving quickly, so you need some skills to see it,” he said Juan Luis Canomember of the Planetary Defense Office of the European Space Agency.
Stargazers in the United States, especially those farther southwest, will be able to see the asteroid zip past the planet. Those atop the Mauna Kea volcano in Hawaii will be well-positioned to see it as the asteroid zooms past before sunrise. However, those in South America may have the easiest viewing experience Andrew Rivkina planetary astronomer at the Johns Hopkins University Applied Physics Laboratory.
Small asteroids and comet fragments occasionally pierce Earth’s atmosphere, creating a harmless light show. Many more rocky and icy shards just miss the planet and often squeeze between the Earth and the moon.
An asteroid the size of 2024 MK threading this celestial needle is less common. “Things this big pass this close are rare, but happen on decadal timescales – this will be the third (that we know of) this century,” Dr. Rivkin said in an email.
Anyone who doesn’t see 2024 MK doesn’t have to feel left out for too long. On April 13, 2029, Apophisa 350-meter-long asteroid, will fly less than 32,000 kilometers 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 are being pinged by radar systems on Earth, making it possible to accurately determine their sizes and onward travels.
“These measurements will significantly reduce uncertainties in their movement and allow us to calculate their trajectories further into the future,” said Lance Bennerthe principal investigator of the asteroid radar research program at NASA’s Jet Propulsion Laboratory.
The double flyby also serves as a coincidental preview of Asteroid Day on June 30 — an event supported by the United Nations and aimed at raising awareness about asteroid impacts.
On that day in 1908, a space rock about 50 meters (164 feet) across exploded over a remote part of Siberia, instantly leveling 500 square miles (800 square kilometers) of forest—roughly the size of the Washington, D.C., metro area. It’s known as the Tunguska Event, after a river that ran through the region it devastated.
Although more are discovered every year, most asteroids found near Earth are capable of destroying a city, though still to be found. Fortunately, many more can be observed through a pair of telescopes under construction: Chile’s multi-purpose Vera C. Rubin Observatory and NASA’s Near-Earth Object Surveyor spacecraft.
The 2024 MK asteroid is at least twice as long as the Tunguska impactor. It is certainly welcome that the asteroid was found before its close encounter with Earth, and that it will miss us. But astronomers only discovered the space rock on June 16.
“The case of 2024 MK is yet another reminder that there are still many large objects to be found,” said Dr. Cano. Space agencies have the plans and technology to defend the planet from deadly asteroids — but only if they find them before the asteroids find us.
