Starship Asterisk*

Asteroids, unlike comets, do not usually present tails, but there are some twenty exceptions to this rule. P/2016 J1 is a peculiar case, known as an “asteroid pair”, resulting from the fracture of a parent asteroid

[img3="Images of the P/2016 J1 asteroid pair taken on May 15th, 2016. They show a central region, the asteroid, and a diffuse blot corresponding to the dust tail. (Credit: F. Moreno et al, ApJL, 2017)"]http://www.iaa.es/sites/default/files/b ... 016_j1.jpg[/img3][hr][/hr]

Asteroids on the main belt, situated between Mars and Jupiter, move around the Sun in quasi circular orbits, so they do not undergo the temperature changes which, in comets, produce the characteristic tails. Nevertheless, some twenty cases have been documented of asteroids which, for various reasons, increase their glow and unfurl a tail of dust. Among the latter stands P/2016 J1, the youngest known “asteroid pair.”

Asteroid pairs are relatively frequent objects in the main asteroid belt. They are created when an original asteroid, either because of an excess of rotational speed or because of an impact with a foreign body, breaks in two. This can also happen as the result of the destabilization of binary systems. Asteroids that form pairs are not gravitationally linked to each other. They drift away from each other progressively, but they plot similar orbits around the Sun.

Reconstructing the orbits of asteroid pairs, astronomers can determine the moment of maximum proximity, and thereby establish the asteroid’s date of rupture. ...

• Astrophysical Journal Letters 837(1):L3 (2017 Mar 01) DOI: 10.3847/2041-8213/aa6036
  arXiv.org > astro-ph > arXiv:1702.03665 > 13 Feb 2017