Mile-wide asteroid discovered hiding under sun’s glow

On a beautiful spring day 66 million years ago, a killer asteroid came from space and crushed the dinosaurs to extinction. They couldn’t have seen it coming or done anything about it, but maybe we can. If the events of Asteroid versus Earth (now streaming on Peacock!) never come true and we come face to face with another killer space rock, our only hope will be to see it with enough advanced warning to knock it off course (as tested by the recent Dart mission from NASA).

It’s a relatively simple undertaking – in principle if not in practice – for things from outside the solar system. All we have to do is point our telescopes at the night sky and watch. Objects large enough to truly threaten Earth aren’t that hard to find, but things can get tricky when looking inside the solar system. Indeed, looking at things more closely means facing the Sun. It’s the astronomical equivalent of trying to see someone’s face when they’re standing in the spotlight, and you don’t know exactly where they are or if there’s a person there.

That’s why, so far, astronomers have only identified about 25 asteroids with orbits entirely inside Earth’s orbit. This may in part be due to their relative rarity, compared to objects farther away than us, but it is certainly due to the difficulty of seeing inside the Sun’s glow. To make matters worse, many telescopes aren’t designed to look or point at the Sun. Scientists needed a specialized instrument to observe the right parts of the sky, and they found it in Chile.

There, an international team of scientists used the Cerro Tololo Inter-American Observatory’s Dark Energy Camera to scan the sky at dusk. Each day there were only two 10-minute windows, on the border between night and day, where they could make observations. Despite the laborious and uncooperative circumstances of the work, the researchers managed to identify three new objects orbiting the inner solar system. Their findings were published in The Astronomical Journal.

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Two of these objects, dubbed 2021 LJ4 and 2021 PH27, have orbits that remain entirely within Earth’s orbit. This means that pending any unforeseen disruption, there is little or no risk that they will ever visit us. But there was another object, which could potentially cause problems down the road.

Astronomers have named it 2022 AP7, an asteroid nearly a mile in diameter and the largest potentially dangerous asteroid discovered in the past eight years. Not only does it hang out in the inner solar system, closer to our home than we’d like, but its orbit also intersects with Earth’s, opening up the possibility that the two could one day come into contact. If that’s the case, we could be in trouble. An object of this size would cause damage on several continents. It’s not big enough to wipe out the entire planet, but it would be a particularly bad day.

Luckily for us, he’s unlikely to strike. Sure, its orbit crosses Earth’s path, but that’s true for a lot of objects. The orbits are large and the solar system is bigger, even inside. Asteroids, and even planets, pale in comparison to the size of the paths they take, and the likelihood of two crossing at the same time is low. That said, we’re glad to know that 2022 AP7 does exist, and further research may identify any other potential planet-killers lurking in the Sun’s glare.

Knowing the existence of threats is the first step in planetary defense. We can only approach what we see coming and the work done with the Dark Energy Camera expands our cosmic view. Now that we’re tracking it, if 2022 AP7 or anything else starts to feel feisty, we might be able to do something about it.