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Ces images ont été acquises au moyen de l’instrument Sphere installé sur le Very Large Telescope (VLT) de l’ESO, dans le cadre d’un programme d’étude de 42 des plus grands astéroïdes de notre Système solaire. Elles montrent Cérès et Vesta, les deux objets les plus proéminents de la ceinture d’astéroïdes située entre Mars et Jupiter, dont les diamètres avoisinent les 940 et 520 kilomètres respectivement. Ces deux astéroïdes sont également les plus massifs de l’échantillon constitué. © ESO, Vernazza et al., Mistral algorithm (Onera/CNRS)

Biggest Surprises from Studying the 42 Largest Objects in the Main Belt

An instrument mounted at the VLT’s focal point captured images of 42 of the largest objects in the asteroid belt. These observations reveal a great diversity of particular shapes, ranging from the classical sphere to dog bones, and allow astronomers to trace the geographical origin of asteroids within our solar system. Pierre Vernazza, lead author of the asteroid study published in the journal Astronomy and astrophysicsExplains the scientific usefulness of these unpublished images.

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[EN VIDÉO] These are all known asteroids in our solar system
Look at how many asteroids there are: Here are all the asteroids that astronomers have identified since they were first discovered in 1801. The number of discoveries has actually jumped since the end of the 20th century.

Thanks to very large telescope European Southern Observatory (VLT ESO) based in Chile, Astronomy scientists Got 42 pictures of the most remarkable beings asteroid belt Located between Mars and Jupiter. This sample of asteroids is our largest and best solution to date. These photos were acquired byfield instrument Its main objective is detection and characterization, by means of direct imaging, outer planets giants in orbiting About’stars relatives.

This seemingly innocuous surveillance campaign is getting far more scientific interest than it appears. In fact, obtaining, by means of ground-based telescopes, detailed images of these 42 objects” constitutes a tremendous advance in the study of asteroids, and helps answer the question of life,Universeand at all ESO explains in its file Press release.

« So far, only three major asteroids are in the main belt, Ceres, vista and Lutétia, photographed in a high level of detail, as their paths crossed the path of space probes dawn from NASA And Rashid European Space Agency Says Pierre Vernazza from the laboratoryAstrophysics from Marseille (France) and lead author of the asteroid study published in the journal Astronomy and astrophysics.

From the older ones, Ceres and Vista, to the younger ones, Urania and Osonia

Most of the 42 objects that make up its sample have dimensions greater than 100 kilometres. In particular, the team photographed nearly all asteroids larger than 200 kilometers – 20 of the 23 identified. The two most important objectives of the study are: Ceres and Vesta with diameters of about 940 and 520 kilometers. In contrast, Urania and Osonia, which are only 90 kilometers in diameter, make up the two smallest asteroids in the sample. By combining asteroid shapes and information about them masses, the team was able to observe the great diversity of densities within the sample. The four least dense asteroids, including Lamberta and Sylvia, have a density of about 1.3 grams per cubic centimeter – close to that of coal. On the other hand, denser asteroids, such as Psyche and Kalliope, display densities of 3.9 and 4.4 grams per cubic centimeter, values ​​greater than that of diamond (3.5 grams per cubic centimeter).

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The team noticed that the asteroids studied fall into two different groups

By reconstructing the shapes of the objects, the team noticed that the asteroids studied fall into two different groups. Some have an almost perfect spherical appearance, such as Hygiea and Ceres. On the other hand, others have a special taut shape, such as Cleopatra, similar to a bone in dog.

This great disparity in Thing Densities indicate true differences in composition between asteroids in the sample, and provide astronomers with important clues about the origins of each. Asteroids with lower density would have formed in the most remote areas, that is, outside orbit NeptuneThen they moved to their current locations.

Word from Pierre Vernazza, from the Astrophysics Laboratory in Marseille (France) and lead author of the study on asteroids published today in the journal Astronomy and astrophysics.

Futura: Why 42 asteroids and not say 50 or 100?

Pierre Vernazza: The idea was to sample well the different configuration classes. This is what we have to do. We targeted about 40 objects, and were able to notice 42 (this number is coincidental, it could be 41 or 44).

43NS A larger asteroid too small for the Sphere instrument?

Pierre Vernazza: not at all. There are more than 40 asteroids that can still be seen.

How do these images constitute “tremendous advances in the study of asteroids, and help answer the question of life, the universe and the whole”?

Pierre Vernazza: With the tools of previous generations only Ceres and Vista They can be observed with a sufficient level of detail to properly reconstruct their shape. With a Sphere, we can distinguish a hundred asteroids.

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With this series of photos, what are the most surprising discoveries?

Pierre Vernazza: There are many of them. I think especially of the spherical shape of (10) Hygiea when this body was subjected to a giant shock at the origin of its vast family or on the surface filled with craters (2) Palace Which can be explained by its strong tendency.

Of these images, what finding, if any, is giving you trouble with interpretation or understanding?

Pierre Vernazza: The relatively spherical shape of (31) Euphrosyne that does not stick to it rotation period Short (<6 hours). One might expect an elongated ellipsoid shape, it is not.

From a scientific point of view, what can be said that is not specified in the ESO press release?

Pierre Vernazza: A new idea was proposed in the article that was not included in the press release, that a significant portion of the so-called C-type asteroids (such as Ceres or Hygiea) could be directly associated with P/D-type asteroids and they would therefore, like the latter, transneptunian objects (TNO or Kuiper objects) are implanted. So far, models have only considered types P and D as implanted TNOs. Thus, a large part of the belt can come from distant regions of our region solar system.

What is the next step in your business?

Pierre Vernazza: In the near future, keep using Sphere to search for multiple new asteroids. Our program allowed to detect a file moon About (31) Euphrosyne – We’ll surely find out new moons About other large asteroids (less than 80 kilometers in diameter) that have not been imaged by our program. In the distant future, we plan to useELT (very large telescope) To observe distant objects in our solar system that Trojans and trans-Neptunian objects.

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Will the ELT and its 39-meter-high mirror make a major breakthrough?

Pierre Vernazza: Yes really. It will allow us not only to study smaller asteroids, but also to study craters with dimensions of 10-25 kilometers. We will be able to get detailed images of more asteroids when this observatory is operational at the end of this decade. Having a tool like Sphere on the ELT would even allow us to photograph a similar sample of objects inside Kuiper belt. In other words, we will be able to describe the geological history of a larger sample of small bodies from the Earth’s surface.

We learned that the European Space Agency did not choose the project for your mission to Ceres. Are other important proposals under consideration?

Pierre Vernazza: L ‘This is amazing She judged the scientific goal as very ambitious given the techniques he was currently proficient in. My goal is to keep fighting to pass the Small Objects Mission in the future, perhaps via Partnership with a foreign agency. After the ESA Class S mission. comet objection, free landscaping from the European side in the area of ​​small objects. As a reminder, in 2019, I wrote ” White papers » In response to the European Space Agency (ESA) call for missions 2035-2050.

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