Asteroids in our Solar System are very common as there are an estimated 1.1 to 1.9 million of them that have a diameter larger than 1 kilometer (0.6 miles) located in the asteroid belt between Mars and Jupiter – there are millions more smaller asteroids. And now, astronomers using the European Southern Observatory’s (ESO) Very Large Telescope (VLT) have photographed the 42 biggest asteroids that are located in the asteroid belt.
This is actually the first time ever that so many asteroids have been photographed in such great quality as explained by Pierre Vernazza from the Laboratoire d’Astrophysique de Marseille in France, “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,” adding, “Our ESO observations have provided sharp images for many more targets, 42 in total.”
The majority of the 42 asteroids are larger than 100 kilometers (62 miles). The two largest asteroids are Ceres and Vesta which have a diameter of approximately 940 and 520 kilometers, respectively (584 and 323 miles, respectively). The two smallest asteroids, Urania and Ausonia, each measure approximately 90 kilometers (56 miles).
And not all of them look alike as astronomers have put them in two different categories – those that are spherical in shape (like Ceres and Hygiea) and others that are more odd-looking and “elongated” such as the “dog-bone” asteroid Kleopatra.
Furthermore, the astronomers were able to calculate the masses of these asteroids and realized that they varied dramatically from one another. The four least dense asteroids (these include Sylvia and Lamberta) have a density of just 1.3 grams per cubic centimeter (about the same density as coal). The asteroids with the highest density (these include Psyche and Kalliope) have densities of 3.9 and 4.4 grams per cubic centimeter, respectively (they have a higher density than a diamond).
What this means is that the composition of each asteroid varies as explained by Josef Hanuš of the Charles University, Prague, Czech Republic, “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.” For example, the asteroids with the least amount of density would have formed past Neptune’s orbit and traveled inwards to where they are currently located. Their research was published in Astronomy & Astrophysics where it can be read in full.
Several images of the asteroids can be seen here.