In late 2024, a remarkable discovery was made as astronomers identified asteroid 2024 YR4, which was initially thought to be on a trajectory that posed a potential threat to Earth. Thankfully, further observations confirmed that this asteroid, measuring between 40 to 90 meters in diameter and designated as a “city-killer,” will not collide with our planet in the near future. However, the moon may not be so lucky, as its impact remains a distinct possibility.

Asteroid 2024 YR4 isn’t alone in its perilous path through the cosmos. A much larger asteroid, known as 887 Alinda, measures over four kilometers in diameter and could potentially trigger a global extinction event if it were to collide with Earth. Currently, Alinda is positioned just outside our planet's orbit, while 2024 YR4 crosses our path, but luckily, an impact is not anticipated any time soon.

Asteroid Orbits: The Dance with Jupiter

Both 887 Alinda and 2024 YR4 orbit the sun three times for every one orbit of Jupiter, which takes about 12 years to complete. This synchronized behavior means that these asteroids will return to similar paths every four years, placing them in a cycle that increases their potential risk. The frequency and regularity of these orbits, particularly for 2024 YR4, make them significant objects of study for astronomers.

Notably, 2024 YR4 has been making close passes to Earth approximately every four years since its recognition in 1948, though it flew under the radar for many years. Meanwhile, Alinda, discovered in 1918, has also been observed in close proximity to Earth at similar intervals.

These orbital patterns are a result of gravitational influences from Jupiter, known as Kirkwood gaps — regions in the asteroid belt that are sparsely populated due to the gravitational effects of larger celestial bodies. Such insights weren't fully understood until advanced computing technology enabled scientists to decode the complex movements of asteroids, revealing their potential threats.

Is It Bad News or Just the Beginning?

The discovery that these asteroids are likely to be in alignment, posing a collision risk, raises alarms. The Alinda-class asteroids, including 2024 YR4, follow a rhythm that allows them to come within striking distance of Earth every four years, should the conditions align perfectly. The proximity of these asteroids, particularly given their low tilt to the plane of Earth's orbit, indicates a higher likelihood of impact.

While we can breathe a sigh of relief knowing that 2024 YR4 will miss Earth in 2032, it’s important to remember that this asteroid will still come close enough to be nudged from its current orbit. This means it may not return with the same frequency, but it still poses a potential threat in 2052 and beyond, when its trajectory will cross our path again.

The Threat from Space: Past and Present

Although Earth appears as a small target in our vast solar system, it has not escaped unscathed from asteroid impacts. Recently, we were reminded of this when a small asteroid exploded over Chelyabinsk, Russia, in February 2013, injuring many and damaging buildings with its shockwave. The infamous Tunguska event in 1908 similarly devastated a large forested area in Siberia, although injuries were minimal.

Keeping Vigilant: The Future of Asteroid Detection

With the risk of asteroid impacts looming, astronomers are actively working to track these celestial bodies. Space-based surveys, like the upcoming Near-Earth Object (NEO) Surveyor, set to launch in late 2027, will revolutionize our detection capabilities, specifically designed to find potentially hazardous asteroids more efficiently.

Currently, it is estimated that we are only aware of approximately 40% of the larger asteroids that could cause significant regional damage. Once operational, the NEO Surveyor aims to identify and monitor 90% of these threats, ensuring that we know when — and if — they are coming our way.

In conclusion, while we rejoice in avoiding the impending threat of asteroid 2024 YR4 in 2032, we must remain vigilant. Resonant asteroids like it will continue to make their unwelcome appearances, reminding us that our cosmic neighborhood harbors dangers that we cannot afford to ignore.