Our solar system is teeming with asteroids of all kinds – they come in all shapes and sizes. But, to see them, many times due to their “small” size, and how dim they are, they are usually overshadowed by other larger objects and it is much more difficult for us to detect them. Now, a team of astronomers from the European Southern Observatory, ESO, detail 42 objects, which represent a step forward in asteroid exploration.
Asteroids are the debris left over from the creation of the planets in our solar system and, as such, they contain information about how things were billions of years ago.
“Only three large main belt asteroids, Ceres, Vesta and Lutetia, have been photographed with a high level of detail so far, as they were visited by NASA’s Dawn and Rosetta space missions and the European Space Agency, respectively,” explains Pierre Vernazza, from the Laboratoire d’Astrophysique de Marseille in France, who led the study of asteroids published in the journal Astronomy & Astrophysics. “Our ESO observations have provided sharp images for many more targets, 42 in all.”
42 of the largest objects in the asteroid belt
To date, NASA has counted more than 1 million asteroids and now, thanks to the Very Large Telescope, we have images of the 42 largest. The new 3D data helps show the shape and mass of these mysterious asteroids. By reconstructing the shapes of the objects, the team realized that the observed asteroids are mainly divided into two families. Broadly speaking, the objects fall into two groups: rocks that are almost round and rocks that are more elongated, Cleopatra being the most extreme illustration of the second, the “dog bone” shaped asteroid.
Thus, astronomers have captured images of the 42 largest objects in the asteroid belt between Mars and Jupiter, including some with unusual shapes and structures, as we just cited.
The team behind this new study, led by the Laboratoire d’Astrophysique de Marseille in France, says it is helping astronomers trace the origins of asteroids in the solar system.
The previously small number of detailed asteroid observations meant that key features, such as their 3D shape or density, had remained largely unknown.
Most of the 42 objects are more than 100 km in diameter, including some, like Ceres, which is 940 km in diameter.
According to the data, the less dense asteroids had densities of around 1.3 grams per cubic centimeter, roughly the same density as coal, suggesting a carbonaceous and porous composition (remember that Earth’s is 5.51 grams per cubic centimeter). The most dense were Psyche and Kalliope, with densities of 3.9 and 4.4 grams per cubic centimeter respectively , denser than diamond, suggesting a stony iron composition.
These findings were made possible by the sensitivity of the spectropolarimetric high-contrast exoplanet search instrument (SPHERE) at the VLT.
When the ELT ( Extremely Large Telescope ) is ready, which is currently under construction in Chile, images of asteroids with even more detail than these await us.
“ELT observations of main belt asteroids will allow us to study objects with diameters of between 35 and 80 kilometers, depending on their location in the belt, and craters of up to approximately 10 to 25 kilometers in size,” Vernazza clarifies.
Referencia: P. Vernazza et al, VLT/SPHERE imaging survey of the largest main-belt asteroids: Final results and synthesis, Astronomy & Astrophysics (2021). DOI: 10.1051/0004-6361/202141781
