Astronomers study a new and unique typology of asteroids: cometary asteroids. Unlike other typologies, active asteroids show one or several tails whose origin they try to reveal. Of the more than seven hundred and fifty thousand asteroids discovered to date, only a few dozen are in this category.
The investigations carried out during the last years by a group of astronomers led by Javier Licandro and Fernando Moreno of the Institute of Astrophysics of the Canary Islands (IAC) and of Andalusia (IAA), respectively, focus on determining what are the causes that are causing the appearance of this feature so characteristic in some asteroids.
Another aspect of interest is its origin. Are they cometary in nature or are they “common” asteroids originating in the Main Belt region? Whatever the answer, these objects have been called active asteroids, although by their resemblance to comets are also known as “Comets of the Main Belt”.
The first active asteroid discovered in 1996 was 7968 Elst-Pizarro . Its detection aroused the interest of astrophysicists and since then research is underway to better understand the nature of these unique objects.
The scientific value of these asteroids is that they can provide information about the processes of fragmentation and debris production, as well as the presence of ice inside them; or maybe they can offer information about the internal structure of these bodies.
It has been hypothesized that these singular objects come from cometary orbits and that they were captured in some regions of the Main Asteroid Belt during the early stages of the formation of the Solar System. Although there is also the possibility that they had their origin in own Main Belt and that certain processes are causing the sublimation of particles, recreating behind a tail similar in appearance to that of comets.
In the studies carried out by the IAC and the IAA, they have focused on the analysis of some of the active asteroids recently discovered. In total, twelve objects have been analyzed using images obtained with the Gran Telescopio de Canarias and the OSIRIS camera / spectrograph. The contrast of the high resolution images versus the images generated with numerical models has allowed to recreate the circumstances that could be causing the ejection of material.
Among the causes of these detachments of material would be the excessive speed of rotation of some asteroids that would cause the instability of the internal structure, which could reach the fracture of the asteroid. Thermal disintegration would be another cause. The forces caused by the thermal expansion of the materials would cause cracks in the asteroid with the consequent production of dust and rocky debris.
In previous studies carried out by the Institute of Astrophysics of the Canary Islands, it was suggested that asteroids composed of hydrated minerals could undergo a process of dehydration and sublimation of water.
The asteroids are relics of the different stages of the formation of the solar system and their study helps to understand the accretion processes that gave rise to the origin and evolution of our planetary system as we know them today.