ESO releases images of the solar system's 42 largest asteroids with the most peculiar shapes

The sharpest images of 42 of the largest asteroids in our solar system have been released by the European Southern Observatory (ESO). The detailed images, which were captured by the ESO’s Very Large Telescope (VLT) in Chile, were put out with the date of release and number being a tribute to science fiction writer Douglas Adams.

The observations about the asteroids, which were located between Jupiter and Mars, reveal a wide range of peculiar shapes of the asteroids, from dog-bone to spherical. The research is helping astronomers in tracing the origin of asteroids in our solar system.

This image depicts 42 of the largest objects in the asteroid belt, located between Mars and Jupiter. Image Credit:
ESO/M. Kornmesser/Vernazza et al./MISTRAL algorithm (ONERA/CNRS)

Researchers realised that the observed bodies can be divided into two families after reconstructing their shapes. Some of the asteroids were perfectly spherical such as Ceres and Hygiea, while there were others with a more “peculiar, elongated” shape, chief among them being Kleopatra, the dog bone asteroid.

Many of the objects were larger than 100 kilometres in size, with the Ceres and Vesta, being the two largest objects at 940 and 520 kilometres respectively.

According to Pierre Vernazza from the Laboratoire d’Astrophysique de Marseille in France, only three large main asteroids belts, Ceres, Lutetia and Vesta, have been imaged with a high level of detail till date as they were visited by the space missions of the European Space Agency and NASA, Rosetta and Dawn, respectively.

Vernazza and his team had undertaken a thorough survey of the major bodies in the asteroid belt between 2017 and 2019, the results of which were published in Astronomy & Astrophysics on 12 October 2021.

The latest images of 42 asteroids mean several key characteristics such as their density of 3D shape, which had previously remained largely unknown. By combining the shapes of the asteroids with information on their masses, Vernazza and his team found that the density of the objects varied considerably across the sample size.

The four least dense asteroids, which included Sylvia and Lamberta, had densities of approximately 1.3 grams per cubic centimetre, roughly equalling the density of coal. The densest asteroids were Kalliope and Psyche, which had densities higher than that of diamond, equalling 4.4 and 3.9 gram per cubic centimetre respectively.

The results support the theory that the least dense asteroids migrated to their present location after they were formed in the remote regions beyond the orbit of Neptune. According to Josef Hanuš of the Charles University, Prague, the study provides “strong support for substantial migration of these bodies since their formation,” adding that this was the only explanation for the variety in their composition.

The sample number of asteroids was chosen as a tribute to the series The Hitchhiker’s Guide to the Galaxy by Douglas Adams, which was published 42 years ago on the same date. Referencing the writer, ESO said that the images were “a leap forward in exploring asteroids, made possible thanks to ground-based telescopes, and contribute to answering the ultimate question of life, the universe, and everything".

In the book, the number 42 is said to be the answer to the same ultimate question.