New astronomical family

Unesp researchers supported by FAPESP discover a new class of asteroids in Solar System

By Mônica Pileggi

Agência FAPESP – A new family in the asteroid belt of the v6 secular resonance has been discovered by Valério Carruba, a physicist, PhD in astronomy and professor in the Mathematics Department at Universidade Estadual Paulista (Unesp).

The asteroids in this configuration move in resonance with Saturn. This means that the precession frequency g – or the frequency associated with the pericenter spin-- of the asteroids is equal to the precession frequency of the g6 planet. This phenomenon is called linear secular resonance.

“It is the first time that we have found a family of asteroids in its original configuration forming a stable island of this type of resonance in the Solar System. Because it is linear, v6 is very efficient in increasing the eccentricity of asteroids, making it one of the main resonance destabilizers in the Solar System,” comments Carruba to Agência FAPESP. Carruba coordinates the research project Dynamics and origin of asteroid families, supported by FAPESP as a Young Investigators Award.

In total, there are 110 celestial bodies in the island of stability, 90 of which are members of the Tina family, which formed millions of years ago when asteroids collided and has remained intact in the midst of v6’s celestial agitation.

According to Carruba, this unique characteristic of Tina prevents its members from moving towards the sun or outside the belt. This union within a protective bubble owes largely to the limited eccentricity values – the measure of the circularity of elliptical orbit – reached by asteroids in this configuration.

“In order to maintain this balance, the value must be between zero and 0.4. Higher values initiate close encounters with planets and could cause losses,” he explains.

In an article published this past January in the Monthly Notices of the Royal Astronomical Society, Carruba and Alessandro Morbidelli of France’s Université de Nice Sophia-Antipolis, describe another novelty.

The scientists obtained an estimate on the asteroid family’s age and discovered that the collision which created the group occurred some 170 million years ago.

According to the Unesp professor, the asteroids on the horizon of v6 are very unstable because they are lost in a relatively short time scale of 2 million to 10 million years.

“Tina is part of a new class of asteroids. The scientific community, however, had already discovered resonances of 2:1 and 3:2 of average movement with Jupiter. Both have islands of stability and a population of objects in these regions. However, this is the first time that a family of asteroids has been found in an island of stability with linear secular resonance,” he affirms.

The article On the first ν6 anti-aligned librating asteroid family of Tina (doi:10.1111/j.1365-2966.2010.18083.x) by Valério Carruba and Alessandro Morbidelli can be read in Monthly Notices of the Royal Astronomical Society at onlinelibrary.wiley.com.