The asteroid 2023 DW was just discovered in late February. But NASA says it's tracking it closely to learn about its orbital path, because the asteroid "has a very small chance of impacting Earth" in 23 years.
The asteroid's diameter is listed at nearly 50 meters — roughly the size of an Olympic swimming pool. It takes 271 days to orbit the sun.
NASA says that, after a new object is first discovered, "it takes several weeks of data to reduce the uncertainties and adequately predict their orbits years into the future."
As for how small the chance of impact is currently estimated to be, NASA puts it at "1 in 560 odds of impact." Put another way, there is only a 0.18% chance of hitting Earth, or a 99.82% chance that the asteroid will streak harmlessly past our planet.
Asteroid 2023 DW currently tops the "Risk List" maintained by the European Space Agency — a roster of 1,450 near-Earth objects "for which a non-zero impact probability has been computed."
Similar-sized objects have hit Earth
Even if the asteroid were to strike our planet, it wouldn't be expected to create a broadly cataclysmic event. Objects of similar size have hit Earth before, including the impact some 50,000 years ago that left the Meteor Crater in modern-day Arizona.
And in 1908, Siberian forestland was devastated in the "Tunguska Event" that tore up 800 square miles of land and blasted 80 million trees, leaving them splayed in a radial pattern.
The science of hazard ratings
There are two impact hazard scales: the Palermo Scale, which specialists use to impart a granular look at the potential risks posed by near-earth-objects, and the older Torino Scale, which uses color codes and a 0-10 rating to communicate possible risks to the public.
NASA explains how the Palermo Scale works:
"For convenience the scale is logarithmic, so, for examples, a Palermo Scale value of -2 indicates that the detected potential impact event is only 1% as likely as a random background event occurring in the intervening years, a value of zero indicates that the single event is just as threatening as the background hazard, and a value of +2 indicates an event that is 100 times more likely than a background impact by an object at least as large before the date of the potential impact in question."
Asteroid 2023 DW is one of only three objects that currently have a Palermo Scale value greater than -3, listed at -2.17 on the ESA's website.
On the Torino Scale, Asteroid 2023 DW is currently the only object with a value of 1 — a designation that applies to a "routine" event in which a near-Earth pass "is predicted that poses no unusual level of danger."
On the scale's color-coded chart, 1 is green. For objects in that category, NASA says, further observations "very likely will lead to re-assignment to Level 0," which represents the "no hazard" zone.
