Researchers have found over 1,700 asteroid trails in archived Hubble data from the last 20 years. While many of the asteroids are previously known, more than 1,000 are not. What good are another 1,000 asteroids? Like all asteroids, they could hold valuable clues to the Solar System’s history.
As time passes and more and more telescopes perform more and more observations, their combined archival data keeps growing. Sometimes discoveries lurk in that data that await new analytical tools or renewed efforts from scientists before they’re revealed. That’s what happened in an effort called the Hubble Asteroid Hunter.
In 2019 a group of astronomers launched the Hubble Asteroid Hunter. It’s a citizen science project on the Zooniverse platform. Their goal was to comb through Hubble data to find new asteroids.
“The amount of data in astronomy archives increases exponentially and we wanted to make use of this amazing data.”
Sandor Kruk, Max Planck Institute for Extraterrestrial Physics.
The astronomers released the results of their project in a new paper titled “Hubble Asteroid Hunter I. Identifying asteroid trails in Hubble Space Telescope images.” The study is online in the journal Astronomy and Astrophysics. The lead author is Sandor Kruk from the Max Planck Institute for Extraterrestrial Physics.
“One astronomer’s trash can be another astronomer’s treasure,” Kruk said in a press release. The data they searched for was largely discarded from other observational efforts not focused on asteroids. In many cases, the data would have appeared as “noise” and was removed to make different elements stand out. But all of this secondary, unexamined data is still archived and available. “The amount of data in astronomy archives increases exponentially, and we wanted to make use of this amazing data,” said Kruk.
The project examined more than 37,000 composite Hubble images. They were taken between 30 April 2002 and 14 March 2021 with the Advanced Camera for Surveys and the Wide Field Camera 3 onboard the Hubble Space Telescope. Most images are 30-minute long exposures, so asteroid trails appear as curved streaks.
In this Hubble observation taken on 5 December 2005, the Main Belt asteroid 2001 SE101 passes in front of the Crab Nebula. Image Credit: NASA/ESA HST, Image processing: Melina Thévenot.
The streaks go to the heart of the problem: computers struggle to detect them. That’s where the Zooniverse platform and citizen scientists come in.
“Due to the orbit and motion of Hubble itself, the streaks appear curved in the images, which makes it difficult to classify asteroid trails – or rather it is difficult to tell a computer how to automatically detect them,” explained Sandor Kruk. “Therefore, we needed volunteers to do an initial classification, which we then used to train a machine-learning algorithm.”
The volunteers delivered. 11,482 citizen scientists took part in classifying the images. The Hubble Asteroid Hunter page at Zooniverse had over 2 million clicks, and the volunteers provided 1488 positive classifications in about 1 % of the images.
This image shows the Hubble Asteroid Hunter interface
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