By Dylan, Guest Writer and Adler Zooniverse Summer ’22 Teen Intern

Every once in a while, you get an opportunity that’s so cool, you sort of can’t believe that it’s happening. When I was told that I would have the chance to interview Dr. Colin Orion Chandler, a (then) grad student at Northern Arizona University, who is responsible for creating and leading the Active Asteroids project on Zooniverse, I was beyond thrilled. Every year, the Adler Planetarium in Chicago hires several interns to fill a variety of placements around the museum. As Zooniverse interns, Lola Fash, Tasnova, and I got to interview several researchers on three different projects: Transcribe Colored Conventions, NASA GLOBE Cloud Gaze, and my focus, Active Asteroids. 

What are active asteroids, and why should we care?

Active asteroids are bodies that follow a typical orbit for an asteroid, but, when observed, they are seen to have comae, which are clouds around the object, and tails, which form when water, dry ice, or dust streak out behind the object. These bizarre objects are extremely rare, so we don’t know much about them, but their tails and comae lead researchers to believe that they might have water on them. According to Dr. Chandler, “Water gives us fuel power. Things that we need to drink, to live, gives us things to breathe. It lets us grow food. I mean, it does a huge number of things. But you have to actually know where you might find it and how hard it is to get out of there.”

The hunt for active asteroids

Studying active asteroids could yield remarkable amounts of scientific information, but they are so faint that scientists have trouble finding them. However, the Dark Energy Camera in Chile is sensitive enough to photograph these asteroids, and it sometimes catches an asteroid in part of an image when it was photographing a different object altogether. 

To get data from these archived images, Dr. Chandler and his team break the images into chips, cut out the asteroid, and then focus and enhance the image so that, if there is a tail, we will be able to see it. Will Burris, one of Dr. Chandler’s students, has helped streamline this process. All of these steps have been automated so that computers can process the nearly 30 million images that could contain active objects, and narrow it down to about 10 million where the objects are most likely to appear. 

The next step in the process is to identify whether or not there is a tail or coma around the object in the image, and that’s where volunteers come in. Computers are unable to identify active asteroids with a reasonable degree of accuracy, so the task falls to human minds. But, because of the sheer volume of images, Dr. Chandler and his team are unable to process them on their own. Instead, they harness the power of the crowd to classify these images for them, so they can process the data in a reasonable amount of time. When we spoke, Dr. Chandler explained why he opted to go this route, and why he chose to use Zooniverse specifically, stating that, without Zooniverse “It [Active Asteroids] wouldn’t have been as successful, not even by a fraction.”

Once Zooniverse volunteers have fully sorted the data, Dr. Chandler and his team examine the results and single out promising candidates that should be followed up on later with different telescopes. William Oldroyd, in particular, helps with this process. One improvement he’s looking to make is discarding feedback from overly optimistic citizens. Some citizens flag far more asteroids as active than what truly exists, which can throw off the data collected by the Active Asteroids team. The observation and analysis team hopes that they will be able to separate these overly optimistic classifications from the rest, so that they can improve the accuracy of the data that comes in. 

With a complete dataset, Dr. Chandler as well as his project co-founder, Jay Kueny, and their chief science advisor, Chad Trujillo, examine the results. If an object was flagged as active, they follow up in one of two ways; direct observation and archival research.

Studying active asteroids

Pointing a telescope directly at a candidate active asteroid to look for more signs of activity seems like the most obvious way to confirm whether or not it is active. However, this is often difficult for several reasons. 

For one, many candidates are so faint that it can be difficult for even the most advanced telescopes, such as the James Webb Space Telescope, to pick them up. 

For another, they can only be observed at certain times in their orbits, and those intervals are usually years apart. Even if an asteroid is visible, it might not be active at that time, since there are many different reasons that an asteroid becomes active, and they each result in different patterns in activity. In an impact event, activity is temporary and only associated with the collision. Likewise, in the event of a rotational breakup, which occurs when an asteroid spins too quickly and falls apart as a result, an asteroid will only have activity corresponding with breakup events.

The asteroids that are most likely to show repeated activity are asteroids that are active due to sublimation, a process in which, as the asteroid gets closer to the Sun, the frozen carbon dioxide and water on its surface turn into gas and form a coma and tail behind it. Although this is a recurring event, a formerly active asteroid will not always be sublimating, so even if it can be observed, activity might not be detected. 

For all of these reasons, when an object is identified as a promising candidate for activity, researchers prefer to follow up by looking through archived images that contain that object. When we talked, Dr. Chandler referred to “archival investigations” as “instant gratification” since he did not have to deal with the limitations of direct observation, and he could immediately confirm activity and further investigate the object by using images that were already taken. 

Dr. Chandler and his team have already used the results from Active Asteroids to find and study several promising objects, and they are in the process of publishing their findings.

Reflections on my experience

All in all, working as a Zooniverse intern and learning about Active Asteroids has been an amazing experience. Going into the interview, I was worried that Dr. Chandler would be unapproachable and difficult to talk to. However, he seemed more than happy to discuss his work with me, and we actually talked well beyond the time when I’d originally expected the interview to stop. We were able to talk not just about Active Asteroids, but also what it’s like to be an LGBTQ+ person pursuing a career in science. As a young trans person, I often feel like I lack a connection with adults in my community, so getting to talk to someone with an identity similar to mine who was successfully pursuing a career in the field I aspire to join was an incredibly powerful experience. I wish I had a larger word count and some more time since I feel like I could probably write a whole book on interning at the Adler Planetarium and studying the Active Asteroids project on Zooniverse.

When I originally heard about active asteroids, I was mildly intrigued, but not all that excited about writing about them. Although I love all things space related, six months ago I would have said that asteroids are just about the most boring thing in space. However, after having done this project, I’ve become enthralled by active asteroids, and small planetary bodies in general. The idea of all the smaller rocks, tumbling through strange orbits in all kinds of places around the Sun, some with water or other invaluable resources that we may never even find, has found a special place in my heart. I hope this blog post has given you a piece of that.