The chances of this asteroid hitting Earth keep rising. But there are three reasons I’m not worried yet | Carrie Nugent

Two days after Christmas, the Atlas sky survey team discovered a new rocky object in Earth’s astronomical neighbourhood. Atlas discovers near-Earth objects all the time: in 2024, the team discovered 167 of them. They also codiscovered comet Tsuchinshan–Atlas, which dazzled sky gazers last autumn. But this discovery was special: there’s a chance the 40-90 metre object, known as 2024 YR4, will hit Earth in 2032.

In January, the impact probability was estimated to be just over 1%, then it was raised to 2.3% in early February. As of this week, the Nasa JPL Center for Near Earth Object Studies has raised that to 3.1% – or about 1-in-32 chance of impact.

There are four reasons I’m not worried just yet. First, the possible impact would be in December 2032, so we’ve got time to prepare. Second, the asteroid is likely not terribly large by asteroid standards. The little asteroid that unexpectedly exploded over Chelyabinsk in Russia, causing damage but no deaths in 2013, was roughly 20 metres across – 2024 YR4 is bigger than that but still vastly smaller than the 10km-diameter object that caused the extinction of the dinosaurs. If 2024 YR4 hits, it would cause regional, not global, destruction. And with years to prepare, people have time to evacuate the area.

Which brings us to the third reason not to panic – the surface of the Earth is mostly water. And although asteroid-tsunami studies could use more research, I think most experts would agree that a 40- to 90-metre asteroid-ocean impact could happen without loss to human life or property.

Fourth, we are still gathering data on this object. The impact probabilities come from specialists using computer software to figure out where 2024 YR4 might go. The timing here is important. For an asteroid to hit the Earth, you don’t just need the asteroid’s orbit and the Earth’s orbit to cross. You need both Earth and the asteroid to be in the same place in the solar system, at the same time.

You can picture these trajectory predictions as a line of possibilities showing where the position of the asteroid might be in December 2032. Right now, , 3.1% percent of the line overlaps the surface of the Earth. As astronomers gather more observations of this asteroid, they’ll become more confident about what its path will be, and the line of possibilities will shrink.

As the line shrinks, the Earth-overlapping portion becomes a larger fraction of it. That can make the impact probability go up – at first. This has happened before with newly discovered asteroids. But as more observations of those objects were made, the line continued to shrink. Eventually, only part, and then none, of the Earth was covered by the likely paths predicted in the line. When that happened, the impact probability rapidly dropped to zero. We will have to wait and see what happens to 2024 YR4’s impact probability.

Asteroid impacts are often represented, in media and literature, as a symbol of human powerlessness against the universe. But the reality is quite different. A few years ago, Nasa significantly changed the orbit of an asteroid. The Dart spacecraft slammed into a 150-metre asteroid moon at tremendous speed, changing its orbital period by more than 30 minutes. And although every impact scenario is unique, that’s a promising result – it’s enough of a kick to knock many objects off course, causing them to miss Earth. However, the remaining time before 2024 YR4’s possible impact is extremely tight to fund, build and launch such a complex spacecraft.

There’s a community of astronomers, software engineers, citizen scientists and civil servants who spend their days discovering and keeping tabs on every single one of the almost 38,000 known asteroids and comets that pass through near-Earth space. Nasa’s Planetary Defense Coordination Office and the European Space Agency’s Planetary Defence Office, which have similar goals even if they disagree on spelling, have been working with governments and the UN, preparing for something just like this.

Each night, surveys such as Atlas discover near-Earth objects using telescopes. These surveys send their observations to the Minor Planet Center in Massachusetts, which checks them for accuracy and publishes them. This allows other people to point their telescopes at the right part of the sky, at the right time, and get the follow-up observations that secure an orbit. In the case of 2024 YR4, observations have poured in from all over the world – from Kansas, London, Ukraine and China, just to name a few. This collective gathering and publishing of observations allows trajectory-prediction groups in the US and Europe to keep tabs on the new discoveries to see if any have a chance of hitting Earth.

2024 YR4 is worth keeping an eye on. Right now, it’s pretty faint, and the full moon has been flooding the night sky with light, making it tough to track. Over the coming months, expect to see more observations coming in, including ones from the James Webb space telescope. These observations will tell us more about the object’s size and where exactly it’s headed.

But this smaller object should be a reminder of the bigger near-Earth objects out there. Very roughly, there’s a one in 350 chance that a much larger asteroid – 140 metres across or larger – will hit Earth in your lifetime. This is much more likely than the one in 17,000 chance you have of being struck by lightning. Personally, I’m thankful that the asteroid surveys regularly scan the night sky with their telescopes, keeping watch.