Astronomers hunt down photobombing asteroids in archival Hubble images

An asteroid photobombing Hubble's capture of Galaxy UGC 12158. (Image Credit: NASA, ESA, PG Martín, Autonomous University of Madrid, J DePasquale, STScI, Acknowledgment: A Filippenko, University of California, Berkeley).

Key Highlights

• The faintest asteroids discovered by the survey are millions of times fainter than the faintest stars.
• The asteroids have been identified as part of an exercise started in 2019 called Hubble Asteroid Hunter.
• A total of 11,482 citizen scientists participated in the initiative.

New Delhi: Astronomers used 37,000 images captured by the Hubble Space Telescope over a period of 19 years to hunt down a mostly unseen population of smaller asteroids, most of which occupy the main belt between Mars and Jupiter. The treasure hunt yielded impressive results, with 1,701 asteroid trails spotted. About 1,031 of these asteroids were previously uncatalogued. About 400 of the newly discovered asteroids are below a kilometre in size.

The scientists could not possibly crawl through all the images on their own, and used citizen scientists from around the world to identify the telltale trails of asteroids photobombing Hubble images. Professional scientists combined the efforts of the volunteers with machine learning algorithms, to identify the asteroids. The sport of asteroid hunting has evolved over the years, going from visual observations to photography to automated sky surveys, but this is a new approach.

The discovery helps probe theories on asteroid formation

The same technique can potentially be applied to other datasets. The exercise has resulted in a large, random sample that can provide scientists with valuable insights on the formation and evolution of the asteroid belt. The identification of so many small asteroids supports the theory that many of these space rocks may be fragments of larger asteroids that have interacted, collided and broken up over time, in a grinding-down process that lasts billions of years.

Another theory is that the smaller asteroids formed billions of years ago, but there is no known mechanism that would prevent the asteroids from growing increasingly larger as they attract material under the influence of increasing gravity. Astronomers know of Hubble's position during the capture, and by carefully measuring the curvature of the streaks, the distances to the asteroids can be determined along with an estimate of their shapes and orbits.

The asteroids can help better understand the evolution of the Solar System

A paper describing the findings has been published in Astronomy and Astrophysics. Lead author of the paper, Pablo García Martín says, "We are getting deeper into seeing the smaller population of main-belt asteroids. We were surprised to see such a large number of candidate objects. 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. This is important for providing insights into the evolutionary models of our Solar System."

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