New posters feature the 42 largest asteroids imaged in unprecedented detail

Asteroids are rocky remnants from the early days of the solar system. Too small to be a planet, some of them still reach impressive sizes. Out of the over 1 million asteroids researchers have mapped out, a few dozen are over 100 kilometers in size, with the largest known asteroid, Ceres, being 940 km (580 mi) in diameter — so large it’s considered a dwarf planet.

Using the European Southern Observatory’s Very Large Telescope (ESO’s VLT) in Chile, astronomers have imaged 42 of these largest asteroids, showcasing their unique details.

This poster shows 42 of the largest objects in the asteroid belt, located between Mars and Jupiter (orbits not to scale). The images in the outermost circle of this infographic have been captured with the Spectro-Polarimetric High-contrast Exoplanet REsearch (SPHERE) instrument on ESO’s Very Large Telescope. The poster highlights a few of the objects, including Ceres (the largest asteroid in the belt), Urania (the smallest one imaged), Kalliope (the densest of the imaged asteroids), and Lutetia, which was visited by the European Space Agency’s Rosetta mission. You can buy this poster at the ESOshop.

For many of the asteroids imaged here, it’s the first time they’ve imaged in such detail. Previously, the small number of observations meant we didn’t really know their shape or density.

“Only three large main belt asteroids, Ceres, Vesta, and Lutetia, have been imaged with a high level of detail so far, as they were visited by the space missions Dawn and Rosetta of NASA and the European Space Agency, respectively,” said lead author of the study, Pierre Vernazza of the Laboratoire d’Astrophysique de Marseille in France, in a statement. “Our ESO observations have provided sharp images for many more targets, 42 in total.”

Thanks to the work of Vernazza and colleagues who used ground-based telescopes, we can now see them in more detail than ever before.

This image depicts 42 of the largest objects in the asteroid belt, located between Mars and Jupiter. Most of them are larger than 100 kilometres, with the two biggest asteroids being Ceres and Vesta, which are around 940 and 520 kilometres in diameter, and the two smallest ones being Urania and Ausonia, each only about 90 kilometres. The images of the asteroids have been captured with the Spectro-Polarimetric High-contrast Exoplanet REsearch (SPHERE) instrument on ESO’s Very Large Telescope.

Roughly speaking, the asteroids can be split into two categories: some are round (like Ceres), while others are more elongated — most notably, the “dog-bone” asteroid Kleopatra.

By analyzing the shapes and densities of the asteroids, researchers found that there’s quite the variety among these asteroids. For instance, the density of some (like Lamberta and Sylvia) is around 1.3 grams per cubic centimeter — comparable to that of coal. The densest ones (Psyche and Kalliope) have a density of 3.9 and 4.4 grams per cubic centimeter respectively — higher than the density of diamond.

Ceres and Vesta, the two largest objects in the asteroid belt between Mars and Jupiter, approximately 940 and 520 kilometres in diameter. These two asteroids are also the two most massive in the sample.

The large variety in density suggests that the asteroids’ composition varies significantly, and if this is the case, it indicates that they also formed differently. In particular, it would suggest that the asteroids (which currently lie between Mars and Jupiter, in the so-called asteroid belt), may have formed in a very different place, beyond Neptune, and migrated to their current location.

“Our observations provide strong support for substantial migration of these bodies since their formation. In short, such tremendous variety in their composition can only be understood if the bodies originated across distinct regions in the Solar System,” explains Josef Hanuš of the Charles University, Prague, Czech Republic, one of the authors of the study.

The study was published in Astronomy and Astrophysics.

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About Mihai Andrei

Andrei's background is in geophysics, and he's been fascinated by it ever since he was a child. Feeling that there is a gap between scientists and the general audience, he started ZME Science -- and the results are what you see today.

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