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

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Last September, the world watched with delight as NASA deliberately crashed a spacecraft into an asteroid in a test of planetary defense. The idea of ​​the DART mission was to see if a spacecraft impact could alter the trajectory of an incoming asteroid in the event that such an impending disaster 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 orbit of this asteroid. Scientists then set to work analyzing all the data they had collected for more insights.

Five new articles in the magazine this week 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. While 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 teamed up to observe the impact using small backyard telescopes.

Preliminary data showed that the test had been successful in changing the orbit of this asteroid

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 just minutes. That’s because these telescopes are very sensitive and can observe very distant targets, but it’s difficult to position them precisely to capture a relatively close and very fast-moving object like an asteroid in our solar system.

So it was down to ground-based telescopes to capture as much data as possible from the entire impact event. But getting a good viewing spot wasn’t easy. “At the time of the impact, there weren’t many places on Earth where you could see Didymos, the asteroid,” said Ariel Graykowski of the SETI Institute, lead author of the Citizen Science paper. The edge. “There were only a few places in Africa with good visibility.”

Having a network of telescopes around the world made it possible to make observations from such locations as Nairobi in Kenya and Reunion Island in the Indian Ocean. Graykowski is working with the Unistellar Telescope Network to collect data from both individual telescope users and scientific outreach groups such as the Traveling Telescope Project, which promotes science education in Kenya and which organized a special observation event in Nairobi for the DART impact.

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

The data collected by the network could measure the mass of the ejecta, or how much material was moved by the impact. Combining that with data on the ejection velocity, scientists can calculate how much energy was transferred into the asteroid — showing just how effective the “crash a spacecraft into an asteroid to knock it off course” method is for planetary defense.

“At the time of the impact, there weren’t many places on Earth where you could observe Didymos, the asteroid”

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

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

One of the great benefits of a citizen science network is that it can be used for continuous, ongoing observations. Large telescopes are oversubscribed, meaning more researchers want to spend time on them than can be accommodated, so it’s both hard to get observing time and extremely hard to precisely observe an event as it happens. But with a network, someone is always watching.

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

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