Hear
NEW YORK.- This week, two asteroids —one large enough to destroy a city and another so large it could wipe out civilization—will pass close to our planet.
But don’t panic.
Both have a zero percent chance of hitting Earth. And depending on where you are in the world, you might even be able to see one of them.
The larger of the two, 415029 2011 UL21, will travel more than 17 times the distance of the Moon at 4:14 p.m. Eastern Standard Time (EST) on Thursday. It’s a gargantuan 7,500 feet (2,316 meters) long, but it will be too far away to be easily seen without a powerful telescope.
Two days later, however, the smaller space rock, called 2024 MK, will come fairly close to the planet. On Saturday at 9:46 a.m. Eastern time, it will pass Earth at 75 percent of the distance to the moon. If you have a decent telescope in your backyard or even a good pair of binoculars, and if the sky is clear, you’ll be able to see the 400- to 820-foot rock as a speck of light streaking across the starry night.
“The object will be moving quickly, so you need some skill to detect it,” said Juan Luis Cano, a member of the European Space Agency’s Planetary Defence Office.
Stargazers in the United States, especially those farther southwest, will be able to see the asteroid. Those atop Hawaii’s Mauna Kea volcano will be well positioned to see the asteroid as it passes by before dawn. But those in South America will have the best chance of seeing it, according to Andrew Rivkin, a planetary astronomer at the Johns Hopkins University Applied Physics Laboratory.
Small asteroids and comet fragments occasionally pass through Earth’s atmosphere, creating a harmless light show. Many more rocky and icy fragments miss the planet, often slipping between Earth and the Moon.
The passage of an asteroid the size of 2024 MK happens less frequently. “Asteroids of this size passing so closely are rare, but they occur on decadal time scales; this will be the third (that we know of) this century,” Rivkin said in an email.
Anyone who hasn’t seen 2024 MK need not feel left out for long. On April 13, 2029, Apophis, an asteroid about 335 meters long, will fly less than 32,186 kilometers above the Earth’s surface – closer than the orbits of geosynchronous satellites, meaning it will be visible to the naked eye.
These approaches are useful for researchers in planetary defense. This week’s asteroids will be detected by radars located on Earth, which will allow their dimensions and trajectory to be precisely determined.
“These measurements will greatly reduce uncertainties about their motion and allow us to calculate their trajectories in the future,” said Lance Benner, principal investigator for the asteroid radar research program at NASA’s Jet Propulsion Laboratory.
The double flyby also serves as a preview of Asteroid Day, which falls on June 30, a date backed by the United Nations to raise awareness about asteroid impacts.
On that day in 1908, a space rock about 150 feet in diameter exploded over a remote strip of Siberia, instantly leveling 2,072 square kilometers of forest, roughly the size of the Washington, DC metropolitan area. It is known as the Tunguska event after a river that It flows through the region it destroyed.
Although more are discovered every year, most near-Earth asteroids that could destroy a city have not yet been found. Fortunately, a pair of telescopes under construction—the Vera C. Rubin Multipurpose Observatory in Chile and NASA’s Near-Earth Object Surveyor (NEO Surveyor)—may detect many more.
The asteroid MK 2024 is at least twice as long as the one that hit Tunguska. It is certainly a good thing that the asteroid was discovered before its encounter with Earth, and that it will pass by. But astronomers only just discovered the space rock on June 16.
“The case of 2024 MK is yet another reminder that there are still many large objects left to find,” Cano said. Space agencies have the plans — and the technology — to defend the planet from killer asteroids, but only if they find them before the asteroids find us.
By Robin George Andrews
The New York Times
