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Thursday, October 21, 2021

Asteroids in the solar system. Largest asteroids in images taken by the European Southern Observatory (ESO) telescope

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Astronomers have photographed the 42 largest objects in the main asteroid belt in the solar system between the orbits of Mars and Jupiter. Never before have such clear images been obtained for such a large group of asteroids, the European Southern Observatory (ESO) emphasized. The observations made it possible to determine their density and to know their shapes, and these can be very unusual.

An international team of scientists, including from Poland, has published the results of asteroids (asteroids) observations made with the VLT telescope in Chile belonging to the European Southern Observatory (ESO). Photographs of several dozen of the largest objects in the main asteroid belt between the orbits of Mars and Jupiter are shown.

The press release published by the European Southern Observatory on Tuesday emphasized that accurate pictures for such a large group of asteroids are a leap forward in the study of these objects. The observations show a wide range of strange shapes, from spherical to canine bones, helping astronomers understand the origins of asteroids in the solar system.

42 asteroids photographed in the main asteroid belt between the orbits of Mars and JupiterESO / M. Kornmesser / Vernazza et al./MISTRAL algorithm (ONERA / CNRS)

– So far, only three large objects in the Main Belt – Ceres, Vesta and Lutetia – have been photographed with the appropriate level of detail as they have been visited by the Dawn and Rosetta space missions. Our ESO observations have provided sharp images for many more purposes, 42 in total, said Pierre Vernazza of Laboratoire d’Astrophysique de Marseille in France, who led the research reported in Astronomy & Astrophysics.

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The lack of detailed observations meant that key characteristics of these bodies, such as three-dimensional shapes and density, remained largely unknown. To fill this gap, scientists conducted observations from 2017 to 2019.

Almost perfectly round, oblong, in the shape of a dog bone

Most of the examined objects are more than 100 kilometers in diameter, including almost all the largest ones, measuring more than 200 km (20 objects out of 23 in the main asteroid belt). The largest objects examined are Ceres (940 km) and Vesta (520 km), the first of which is even categorized as a dwarf planet. In turn, the smallest in the analyzed sample are Urania and Ausonia, each about 90 km in diameter.

The asteroids Ceres and VestaESO / Vernazza et al./MISTRAL algorithm (ONERA / CNRS)

The asteroids Ausonia and UraniaESO / Vernazza et al./MISTRAL algorithm (ONERA / CNRS)

The shape reconstruction showed that the observed asteroids are divided into two main families. The first are almost perfectly spherical bodies (for example, Hygiea and Ceres), and the second are objects with unusual, elongated shapes (the most bizarre here seems to be Cleopatra with a shape similar to a dog’s bone). We wrote more about the discoveries about this asteroid at the beginning of September.

Images of the Cleopatra asteroid seen from different angles as it rotatesESO / Vernazza, Marchis et al./MISTRAL algorithm (ONERA / CNRS)

It is known what their density is

By knowing the shapes and combining them with information about masses, it was possible to determine the densities. This parameter turned out to be very diverse. The least dense asteroids are about 1.3 grams per cubic centimeter, which is roughly the density of carbon. The densest, Psyche and Kaliope, on the other hand, have 3.9 and 4.4 grams per cubic centimeter, which is more than diamonds (with a density of 3.5 grams per cubic centimeter).

Such significant differences in density may indicate significant differences in the composition of these bodies, which in turn may mean that they come from different regions of the solar system. So perhaps it is correct to hypothesize that the least dense asteroids arose in the distant regions of the solar system, far beyond Neptune’s orbit, and then migrated to their present positions.

The 42 largest asteroids visible in their orbits in the main asteroid belt between the orbits of Mars and JupiterESO / M. Kornmesser / Vernazza et al./MISTRAL algorithm (ONERA / CNRS)

The Extremely Large Telescope will be able to see even more

Scientists hope that when the Extremely Large Telescope (ELT), currently being built by the European Southern Observatory, begins its observations in a few years, it will be possible to study asteroids with smaller diameters, from 35 to 80 km, as well as craters on their surfaces measuring from 35 to 80 km from the Earth’s surface. 10 to 25 km. It is possible that it will also be possible to properly photograph several dozen objects from the Kuiper belt, which is a cluster of asteroid-like objects much more distant from us.

Among the authors of the article published in the journal “Astronomy & Astrophysics” there are many Polish names: Edyta Podlewska-Gaca, Przemysław Bartczak, Grzegorz Dudziński, Agnieszka Kryszczyńska, Anna Marciniak, Tadeusz Michałowski, J. Krajewski (all: the Astronomical Observatory Institute of the Adam Mickiewicz University in Poznań) and Łukasz Socha (Nieborowice). Astronomers from Poznań specialize in the study of asteroids, in particular in modeling their shapes.

Main photo source: ESO / M. Kornmesser / Vernazza et al./MISTRAL algorithm (ONERA / CNRS), Shutterstock

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