Nearly a year ago, NASA successfully smashed an asteroid for the first time, in a landmark test to see whether we could divert a killer space rock before disaster — but now, the asteroid in question is behaving strangely.
As New Scientist reports, a schoolteacher and his pupils seem to have discovered that the orbit of Dimorphos, the space rock socked by the Double Asteroid Redirection Test (DART) last September, has apparently continued slowing down, unexpectedly, in the year since the refrigerator-sized craft smashed into it.
Jonathan Swift, a math and science teacher at the Thacher School in California, and his team of student astronomers have discovered that Dimorphos, which orbits around the larger near-Earth asteroid Didymos the way our Moon orbits the Earth, has been spinning consistently slower around Didymos than it did prior to the DART test.
To be clear, changing Dimorphos’ trajectory was the point of the DART test.
As NASA announced a few weeks after the collision last fall, it succeeded at doing exactly that, bringing the asteroid’s orbit down a full half hour, from 11 hours and 55 minutes to 11 hours and 23 minutes. Given that the space agency’s “minimum successful orbit period change” was 73 seconds, this meant that the DART test, which showed whether or not Earth can smash near-Earth asteroids out of the way, was a resounding success.
But as Swift and his charges at the Thacher Observatory found when looking at Dimorphos’ orbit more than a month after the initial collision, the asteroid’s orbit seems to have continued to slow down — an unexplained turn of events, considering that most astronomers expected it to return to its original orbit speed pretty quickly.
“The number we got was slightly larger, a change of 34 minutes,” Swift told New Scientist. “That was inconsistent at an uncomfortable level.”
Though NASA did say in its original post-DART findings that the orbit slowing had a margin of error of plus or minus two minutes, the orbit’s change is nevertheless a startling result — though some theories suggest that the impact may have “tumbled” Dimorphos’ orbit, or unlocked it from Didymos’ tidal forces.
“We tried our best to find the crack in what we had done,” Swift expounded, “but we couldn’t find anything.”
NASA will also be releasing a report soon on the DART mission’s latest update, a spokesperson told New Scientist — but the agency will have to compete with Swift and his students, whose findings were shared this summer with the American Astronomical Society, which is publishing their paper soon.
More on asteroids: AI Is Now Identifying Killer Asteroids Before They Approach Earth