By Scott Hamilton
Remember the Double Asteroid Redirection Test (DART) performed by NASA just over a year ago? I wrote about it last October; if you want to refresh your memory you can find two articles on my website at www.techshepherd.org and search for DART. The idea behind the test was to see if they could change the course of an asteroid to prevent a catastrophic collision with earth. The good news is that they succeeded in the test. Just hours after the impact they observed a change in the orbit of Dimorphos.
Several scientists were involved in what they believe to be highly accurate calculations as to the impact they would have on the orbit. They believed they could precisely control and predict the outcome of collision between an asteroid and a spacecraft. The goal was to strike the asteroid in a manner as to increase its speed and reduce the period of its orbit.
According to their calculations they expected the period of the orbit to change by 30 minutes. Given that they were making a lot of guesses in the actual mass of both asteroids involved in the orbital system, they were amazed at the accuracy of their predictions. The actual result was 32 minutes, making the experiment a resounding success, especially considering that it only takes a change of 73 seconds to re-route an asteroid enough to avoid a collision with earth.
It was not until earlier this year that a group of professors at Thacher Observatory made an alarming discovery. Dimorphos was continuing to speed up and was now faster by 34 minutes. This was the opposite of what they expected. Jonathan Swift, a math and science teacher at Thatcher School in California, and his group of student astronomers made the discovery that Swift says, “was inconsistent at an uncomfortable level.” Basically what Swift was pointing out is that we do not have a full understanding of the forces at work in orbital systems.
All the math that we have used for generations to predict planetary orbits apparently depends on more variables.
“We tried our best to find the crack in what we had done but couldn’t find anything,” Swift claimed.
Further study by Jian -Yang Li of the Planetary Science Institute made a discovery that might explain the continued change in the orbit. Li discovered that the collision converted Dimorphos to an “active asteroid,” which is a space rock that orbits like an asteroid, but has a tail of material like a comet. This tail of material means Dimorphos is possibly still crumbling from the impact and losing mass, which will increase the speed of orbit.
As you begin to read more about the DART project you begin to discover a couple of very interesting facts. The first is that science is ever expanding, and even things like orbit calculation can be disrupted with new experimentation. The second is that a lot of scientific discoveries happen by complete accident. You see, prior to Li’s discovery that we had turned Dimorphos into an active asteroid, we did not fully understand the process in nature that caused active asteroids. Now, not only do we have a solid theory to explain their development, we have the full observational videos of one throughout the process of formation.
“DART, as a controlled, planetary-scale impact experiment, provides a detailed characterization of the target, the ejecta morphology, and the entire ejecta evolution process,” says Li.
In other words, we can now study the complete formation of active asteroids, from the first time they start losing material until they form a tail. This will help us understand even more about planetary science.
Until next week, stay safe and learn something new.
Scott Hamilton is an Expert in Emerging Technologies at ATOS and can be reached with questions and comments via email to firstname.lastname@example.org or through his website at https://www.techshepherd.org.