NASA Reveals Images of Large Asteroids That Just Passed By Earth : ScienceAlert

Last week, Earth witnessed a rare event: not one, but two large asteroids, passing close by.

Neither of the asteroids, 2024 MK and 2011 UL21, as they’ve been called, came close enough to Earth to pose a threat, but they were within range of radar imaging systems. So NASA took some happy photos to mark the occasion.

These images aren’t just mementos of asteroid flybys. Scientists can study the images to understand the properties of rocks that might be found in Earth’s vicinity—information that could help us devise strategies to counter any future asteroids that might one day threaten our planet.

The little corner of the solar system that Earth makes up is mostly empty, but not entirely. Every now and then a comet or asteroid passes by as it makes its own orbit around the sun.

The vast majority of these things won’t be a problem. But anything that passes within a certain distance of the Earth, or higher than a certain brightnessIt is classified as potentially dangerous.

This is because its current trajectory may be good, but something unexpected might happen, such as a collision with another object that pushes it onto a collision course with Earth. This is not likely, but it is not impossible either.

Both the MK 2024 and the UL21 2011 were in the potentially dangerous category; fortunately for us, no unexpected oddity caused them to veer off course toward us.

2011 UL21 flew by Earth on June 27, at a distance of 6.6 million kilometers (4.1 million miles), about 17 times the distance between Earth and the Moon.

Less than two days later, 2024 MK appeared. On June 29, it passed at a distance of no less than 295,000 kilometers (184,000 miles). That’s much closer, about three-quarters the distance between Earth and the moon.

Imaging such objects is not easy, even when they are relatively close and classified as “large” asteroids. They are still very small in the scheme of things, and not very bright.

This is why NASA uses large radar telescope To transmit radio waves into space, and receive the reflected signal from which scientists can build images.

And since 2024 MK was much closer — such a close flyby of an asteroid only happens every few decades or so — we were able to get more detailed images.

NASA used one telescope to transmit radio waves and another to receive them, resulting in images of 2024 MK that include not only the asteroid’s shape, but also its bumps, grooves, rocks and hills.

It is about 150 metres (500 ft) wide, and has an elongated shape with many flat planes. It also rolls as it moves through space.

It was only discovered on June 16, and its orbital path has been altered by Earth’s gravity, so the observations allow scientists to see what 2024 MK will do in the future. And they revealed that for the foreseeable future, it will stay safely out of our way. Oh.

“This was an exceptional opportunity to investigate the physical properties and obtain detailed images of a near-Earth asteroid.” Astronomer Lance Benner says From NASA’s Jet Propulsion Laboratory.

Asteroid 2011 UL21, at a much greater distance, didn’t send back detailed images… but those images contained a small surprise. There, along with the 1.5-kilometer-wide asteroid, astronomers spotted a small moon, at an orbital distance of about 3 kilometers.

And this is something we’re discovering more and more with larger asteroids, actually.

Last year, scientists discovered that the asteroid Dinkinesh, one of the objects in the asteroid belt visited by NASA’s Lucy probe, has a small moon. NASA’s famous double-asteroid redirection test, in which a spacecraft collides with an asteroid, was also performed on Dimorphos, the smallest of the pair of binary asteroids.

We’re finding more binary asteroids because our imaging capabilities are improving, which is excellent news for planetary defense and our understanding of the evolution of the solar system.

“About two-thirds of asteroids of this size are thought to be binary systems.” Benner says“Their discovery is particularly important because we can use measurements of their relative positions to estimate their mutual orbits, masses, and densities, which provide key information about how they formed.”

They are so cute. You are welcome my little friend. Come by anytime.