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FAPESP: Four Extremely Young Asteroid Families Identified

Publicado em 25 setembro 2018

Four families of extremely young asteroids have been identified ... The four families in question, all of which are less than 7 million years old, orbit between Mars and Jupiter as part of a grouping known as the Main Asteroid Belt. 

The key dating parameters used were the longitudes of the pericenter and ascending node. For a planet, comet or asteroid moving around the Sun in an elliptical orbit, the pericenter is the point at which it comes closest to the Sun. The ascending node is the point at which the orbit crosses from the southern side of a reference plane, typically the ecliptic plane, to the northern side. ...

In addition to the four new families they themselves identified, the group studied 55 new families identified by other scientists. As well as dating the families, they established a diagram that, with considerable precision, distinguishes between families formed by collisional events and families formed by fission of a precursor body...(http://agencia.fapesp.br/four-extremely-young-asteroid-families-identified/28785/)