The small asteroid 2023 DW could ruin Valentine’s day for a portion of North America in 23 years’ time. The chance of a collision is less than 1 percent, but despite ongoing observations have failed to drop to zero. If 2023 DW does hit, the impact would be more like an atomic bomb going off, without the radiation, than a dinosaur-killing event – but maybe space agencies will get to perform an asteroid deflection for real.
With more telescopes searching the skies for asteroids that could threaten Earth, we’ve started detecting a lot more candidates. In most cases, as soon as an orbit can be calculated, it is obvious there is no threat – at least for hundreds or thousands of years until unpredictable forces pull the object in question onto some quite different path.
Once or twice a year, the asteroid in question is an Earth-crosser that will make a close approach in the next century, and there is a brief burst of excitement at the possibility of a collision. With only a handful of observations, there are always wide margins of error initially, and the chances of an object hitting the Earth are rated as small – one in a few thousand or a few tens of thousands are typical.
Further observations allow us to estimate the newly discovered object’s path more precisely. Usually, these are sufficient to drop the risk to zero, sub-giraffe-sized objects aside. Since its discovery on February 26, 2023 DW has proven an exception. Collision chances are low, but they haven’t changed much over 7 days of observations, moonlight has been interfering since March 5.
NASA’s Center for Near Earth Object Studies currently rates the chance of an impact in 2046 as one in 560, or 0.18 percent. This, they helpfully add, means the possibility of it not hitting is 99.82 percent. If 2023 DW does pass us by in 2046, there will be some subsequent close approaches that may also carry a risk.
2023 DW is estimated to be 47 meters across (155 feet), making it more than twice the width of the object that caused thousands of injuries (but no deaths) when it exploded over Chelyabinsk. Quite how much damage 2023 DW would do in a collision depends on its composition – is it a rubble pile asteroid with plenty of hollow spaces or something denser and more solid? An explosion like the one that leveled forests for many kilometers in Tunguska is currently thought most likely.
On the Torino scale, which combines the chance of impact with the damage a collision would do on a scale of one to ten, 2023 DW is currently rated as 1. That’s not considered a cause for public concern, but it’s currently the only asteroid with a non-zero rating. Apophis, the first asteroid to score higher than 1, reached 4 at its peak but has been rated at zero since 2021.
We might imagine that since no one currently knows whether 2023 DW will hit Earth or miss by up to 15 million kilometers, we can’t have any idea of what part of the planet is most in danger. However, that’s not the case. Modeling based on the best available information provides a line of maximum danger crossing Indonesia across the Pacific Ocean, over northern Mexico, and across much of the United States.
Low as the danger may be, if future observations raise the risk, the success of the DART mission could be highly relevant here. With 2023 DW being less than a third the size of Dimorphos (or nine giraffes if you prefer) it should be a good candidate for orbital alteration.