How a group of amateur astronomers caught a NASA spacecraft crashing into an asteroid

Last September, the world watched with glee as NASA deliberately crashed a spacecraft into an asteroid in a test of planetary defense. The idea behind the DART mission was to see if an impact from a spacecraft could alter the trajectory of an incoming asteroid in the event such a looming catastrophe ever threatened Earth.

The impact and its aftermath were observed by telescopes around the planet and by several in space, including the Hubble and James Webb space telescopes, and preliminary data showed that the test had been successful in altering the trajectory of this asteroid. The researchers then began to analyze all the data they had collected to gain more insight.

This week there are five new articles in the journal Nature reveal more about what happened when the spacecraft hit the asteroid and how effective this method would be in deflecting an asteroid that really threatened Earth. Although four of these papers are based on data from large professional telescopes, the fifth is unusual in that it uses data from citizen scientists – amateur astronomers who worked together to observe the impact using small backyard telescopes.

Space telescopes such as Hubble and JWST were able to see the effects of the impact in great detail, but they missed the impact itself by only a few minutes. That’s because these telescopes are very sensitive and can observe very distant targets, but it’s difficult to move them to exactly the right position to capture a relatively close and very fast moving object like an asteroid in our solar system.

So it was up to ground-based telescopes to capture as much data as they could about the entire collision event. But it was not easy to get a good vantage point. “At the time of the impact, there weren’t many places on Earth where you could observe Didymos, the asteroid,” says Ariel Graykowski of the SETI Institute, lead author of the Citizen Science paper. The Verge. “There were only a few places in Africa that had good visibility.”

Having a network of telescopes around the world made it possible to get observations from these places, such as Nairobi in Kenya and Réunion Island in the Indian Ocean. Graykowski works with the Unistellar telescope network to obtain data from both individual telescope users and science outreach groups such as the Traveling Telescope project, which promotes science education around Kenya and which organized a special observing event in Nairobi for the DART effect.

“Because we have this network, we could see the impact,” Graykowski said, as the network captured both the initial brightness caused by the impact and the subsequent cloud of material, called ejecta, that was thrown up when the spacecraft hit the asteroid. “So citizen science was a very necessary tool.”

The data collected by the network was able to measure the mass of the ejecta, or how much material was displaced by the impact. By combining that with data on the velocity of the ejecta, scientists can calculate how much energy was transferred to the asteroid — and it shows how effective the “crash a spacecraft into an asteroid to knock it off course” method is for planetary defense.

Another interesting oddity discovered by the citizen science network was a color change, with a mysterious redness observed just as the impact occurred. A similar effect had been seen in a previous asteroid impact mission called Deep Impact in 2005, which was thought to be due to optical effects of the dust cloud thrown up.

“So it wasn’t just a fluke in the Deep Impact mission — we’re seeing it here as well,” Graykowski said. Now the question is whether this reddening is actually an optical effect or whether it could be due to the composition of the asteroid’s surface. “And it would be really cool if it was because it tells us about the material that makes up the asteroids, at least on their surfaces. And the asteroids are some of the oldest bodies in the solar system.”

One of the great advantages of a citizen science network is that it can be used for continuous, ongoing observations. Large telescopes are oversubscribed, which means that more researchers will have time on them than there is room for, so it is both difficult to observe time and extremely difficult to observe an event just as it is happening. But with a network, there is always someone watching.

“The most exciting thing is when something falls apart in the sky or something explodes in the sky,” Graykowski said. “We want to know why it happened, and the best way to know is to catch it when it happens. So [the network] has been a really cool tool because we’ve captured things we would never have been able to capture before.”