These are the 42 largest asteroids in the Solar System: they measure more than 100 km

Using the Very Large Telescope (VLT) of the European Southern Observatory (ESO) in Chile, astronomers have obtained images of 42 of the majors objects in the asteroid belt, between Mars and Jupiter.

Never before has it been possible to obtain such sharp images of such a large group of asteroids. The observations revealed everything from spherical to dog-bone-like, which is helping astronomers trace the origins of asteroids in our Solar System.

“So far, only three large main belt asteroids have been imaged in detail, which were visited by the Dawn and Rosetta space missions of NASA and the European Space Agency, respectively ”, explains Pierre Vernazza, from the Astrophysics Laboratory in Marseille, France, who led the asteroid study published in Astronomy & Astrophysics. “Our observations at ESO have provided sharp images for many more targets, 42 in all.”

The small number of detailed asteroid observations meant that their key features, such as their 3D shape, remained largely unknown, until now. Between 2017 and 2019, Vernazza and his team set out to fill this gap by conducting a

Most of the 42 objects in the sample are larger than 100 kilometers. In particular, the team imaged nearly all asteroids larger than 200 kilometers from the belt, which turned out to be 20 out of 23. The team analyzed the two largest objects, Ceres and Vesta, while the two smallest asteroids turned out to be Urania. and Ausonia, which are about 90 kilometers long.

By reconstructing the shapes of the objects, the team discovered that the observed asteroids are mainly divided into two families. Some are almost perfectly spherical, like Hygiea and Ceres, while “enlarged“, With the asteroid “dog bone” named Cleopatra as the undisputed protagonist.

By combining the shapes of the asteroids with information about their masses, the team found that the densities vary in the samples. The four least dense asteroids studied, including Lamberta and Sylvia, have densities of about 1.3 grams per cubic centimeter, roughly the density of carbon. , with 3.9 and 4.4 grams per cubic centimeter, respectively, which is higher than the density of diamond (3.5 grams per cubic centimeter).

This large difference in density suggests that the composition of asteroids varies significantly, giving astronomers important clues about their origin. “Our observations provide strong evidence for a substantial migration of these bodies since their formation. In short, the enormous variety in composition can only be understood if “, explains Josef Hanus of Karlova University, Prague, Czech Republic, one of the authors of the study. In particular, the results support the theory that less dense asteroids formed in remote regions outside of Neptune’s orbit and migrated to their current location.

These discoveries were made possible by the sensitivity of the High Contrast Spectropolarimetric Exoplanet Search (SPHERE) instrument mounted on ESO’s VLT. “With SPHERE’s enhanced capabilities, coupled with the fact that little was known about the shape of the largest asteroids in the main belt, ”says co-author Laurent Jorda, also from the Marseille Astrophysics Laboratory.

Astronomers will be able to image more asteroids in great detail with ESO’s Extremely Large Telescope (ELT), currently under construction in Chile, which will begin operations later this decade. “Observations with the ELT of the main belt asteroids will allow us, depending on its location in the belt, and craters of up to 10 to 25 kilometers “, says Vernazza. “With an instrument similar to SPHERE on the ELT we could image a similar sample of objects in the distant Kuiper Belt. This means that we will be able to characterize the geological history of a much larger sample of small bodies ”.

The results support the theory that less dense asteroids formed in remote regions outside of Neptune’s orbit and migrated to their current location.

Agencies

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