A high school teacher and her students have discovered that an asteroid hit by NASA’s Dart spacecraft last year during an Earth-saving experiment is behaving in an unexpected way. This finding could have implications for future planetary defense missions.
On October 5, 1401, NASA deliberately crashed the “Dual Asteroid Deflection Test” or Dart in short into the asteroid Dimorphos. The goal was to reduce the space rock’s 12-hour orbit around its parent asteroid, Didymus, to see if the spacecraft’s momentum could change the asteroid’s path. The mission was successful, and Dimorphos’ orbit was shortened by 33 minutes in the weeks following the encounter.
Jonathan Swift, a teacher at Thatcher School in California, and his students used the observatory there to track the findings. The school’s 0.7-meter telescope, though small, was large enough to observe the asteroid, allowing students to discover that Dimorphos’ orbit shrank by a minute more than a month after the collision.
swift According to New Scientist He says: “The number we got was a little bigger, 34 minutes. This value is inconsistent at an undesirable level. The students presented their findings at the American Astronomical Society meeting in New Mexico in June and received positive feedback. “We tried our best to find a loophole in our work, but nothing was found,” says Swift.
Observations indicate that a factor has caused Dimorphos’ orbit to slow down continuously since the impact. One possibility is that the asteroid now orbiting was previously in a lethal lock with Didymus, affecting its orbit. According to Swift, “this situation can cause gravitational forces to change the orbital period.”
Harrison Agrosa, a member of the DART team at France’s Cote d’Azur Observatory, says there is evidence for Dimorphos rolling. The asteroid wobbles dramatically after impact. This means that Dimorphos oscillates in relation to Didymus, like the moon does with the earth. As a result, it is possible that depending on the inertia, this wobble can turn into a more chaotic tumbling and cause the asteroid to roll from side to side.
However, Agrosa says it’s unlikely that this tumbling will shorten Dimorphos’ orbit; Because instead, the orbit of the asteroid would change randomly. It is more likely that material ejected by the impact, including boulders several meters wide, remained in orbit near Dimorphos and fell back onto its surface, shortening the asteroid’s orbit. According to Agrosa, “this is the most likely explanation.”
Nancy Chabat, DART coordinator at Johns Hopkins Applied Physics Laboratory in Maryland, says the spacecraft team is continuing to observe Dimorphos and will publish its results in the coming weeks.
The Dart team’s observations also show that the orbital period of the asteroid continued to decrease with a smaller value of about 15 seconds before reaching stability; A finding that may support the idea of ​​the continued return of some thrown material to the surface of the asteroid. “We see no change after about the first month,” says Chabat, referring to observations up until the end of February, when the asteroid was no longer visible from Earth.
An upcoming mission from the European Space Agency, Hera, which is scheduled to reach Dimorphos in 2026, could tell definitively what happened to the asteroid after the impact. This finding may have implications for future efforts to alter the trajectory of asteroids; Because it is important to know exactly how space rocks behave due to impact.
The findings of the study in Archive database It has been published.
