Hubble’s search for small main-belt asteroids intensifies

Astronomers have made a significant discovery using archived images from the NASA/ESA Hubble Space Telescope. By analyzing 37,000 Hubble images taken over a span of 19 years, researchers were able to identify 1,701 asteroid trails, with 1,031 of those asteroids previously uncharted. Of the newly discovered asteroids, 400 are estimated to be smaller than one kilometer in size.

The identification of this asteroid bounty was made possible by the collaborative efforts of “citizen scientists” from around the world, who worked alongside professional scientists and machine learning algorithms to analyze the images. This innovative approach to finding asteroids in astronomical archives has the potential to be applied to other datasets and represents an exciting development in the field of asteroid research.

Lead author Pablo García Martín of the Autonomous University of Madrid expressed surprise at the large number of candidate objects discovered. He stated, “There was some hint that this population existed, but now we are confirming it with a random asteroid population sample obtained using the whole Hubble archive. That’s important for providing insights into the evolutionary models of our Solar System.”

The random sample of asteroids offers valuable insights into the formation and evolution of the asteroid belt. The abundance of small asteroids supports the theory that they’re fragments of larger asteroids that have collided and broken apart over billions of years. This grinding-down process is believed to be responsible for the creation of smaller asteroid fragments. An alternative theory suggests that these smaller fragments formed independently billions of years ago, but scientists have not been able to identify a mechanism that would prevent them from growing into larger sizes over time.

Hubble’s fast orbit around Earth allows it to capture images of wandering asteroids through their unique trails. When viewed from Earth-based telescopes, an asteroid appears as a streak across the picture, or what astronomers affectionately refer to as an “asteroid photobomb.” By measuring the curvature of these streaks and knowing Hubble’s position during observation, scientists can determine the distances to the asteroids and estimate the shapes of their orbits.

The majority of the asteroids identified in this study reside in the main belt, located between the orbits of Mars and Jupiter. Hubble’s sensitive cameras measured the brightness of these asteroids, allowing for a size estimate by comparing their brightness to their distance. The faintest asteroids in the survey were found to be approximately one-fortieth millionth the brightness of the faintest star visible to the human eye.

To sift through the vast amount of data contained in the Hubble archives, the researchers enlisted the help of over 10,000 citizen-science volunteers. These volunteers, through their collective effort, provided nearly two million identifications, which were then used to train an automated algorithm to identify asteroids using artificial intelligence. This pioneering approach holds promise for the analysis of other datasets in the future.

Moving forward, the project will focus on studying the streaks of previously unknown asteroids to determine their orbits and properties, such as rotation periods. However, due to the age of many of these asteroid trails captured by Hubble, it is not possible to observe them in real-time and determine their current orbits.

The findings from this study have been published in the journal Astronomy and Astrophysics and offer new perspectives on our understanding of the Solar System’s evolutionary models. The successful collaboration between professional scientists and citizen scientists demonstrates the power of combining human analysis with machine learning algorithms for groundbreaking discoveries in space exploration.