Title: New observational evidence of active asteroid P/2010 A2: Slow rotation of the largest fragment Author: Yoonyoung Kim, Masateru Ishiguro, Myung Gyoon Lee
We report new observations of the active asteroid P/2010 A2 taken when it made its closest approach to the Earth (1.06 au in 2017 January) after its first discovery in 2010. Despite a crucial role of the rotational period in clarifying its ejection mechanism, the rotational property of P/2010 A2 has not yet been studied due to the extreme faintness of this tiny object (~120 m in diameter). Taking advantage of the best observing geometry since the discovery, we succeed in obtaining the rotational light curve of the largest fragment with Gemini/GMOS-N. We find that (1) the largest fragment has a double-peaked period of 11.36±0.02 hr spinning much slower than its critical spin period; (2) the largest fragment is a highly elongated object (a/b \geqslant 1.94) with an effective radius of 61.9^{+16.8}_{-9.2} m; (3) the size distribution of the ejecta follows a broken power law (the power indices of the cumulative size distributions of the dust and fragments are 2.5±0.1 and 5.2±0.1, respectively); (4) the mass ratio of the largest fragment to the total ejecta is around 0.8; and (5) the dust cloud morphology is in agreement with the anisotropic ejection model in Kim et al. (2017). These new characteristics of the ejecta obtained in this work are favourable to the impact shattering hypothesis.
Strange asteroid has a tail 1 million kilometers long
An odd asteroid's peculiar tail is far longer than previously thought, stretching nearly three times the distance from Earth to the moon, scientists say. The surprising tail of dust streaming from the asteroid P/2010 A2 is about 1 million kilometers long, new photos taken by the One Degree Imager (ODI) camera at the WIYN telescope in Arizona reveal. Source
Title: Dynamics of Large Fragments in the Tail of Active Asteroid P/2010 A2 Authors: Jessica Agarwal, David Jewitt, Harold Weaver
We examine the motions of large fragments at the head of the dust tail of active asteroid P/2010 A2. In previous work we showed that these fragments were ejected from the primary nucleus in early 2009, either following a hypervelocity impact or by rotationally induced break-up. Here, we follow their positions through a series of Hubble Space Telescope images taken during the first half of 2010. The orbital evolution of each fragment allows us to constrain its velocity relative to the main nucleus after leaving its sphere of gravitational influence. We find that the fragments constituting a prominent X-shaped tail feature were emitted in a direction opposite to the motion of the asteroid and towards the south of its orbital plane. Derived emission velocities of these primary fragments range between 0.02 and 0.3 m/s, comparable to the ~0.08 m/s gravitational escape speed from the nucleus. Their sizes are on the order of decimeters or larger. We obtain the best fits to our data with ejection velocity vectors lying in a plane that includes the nucleus. This may suggest that the cause of the disruption of P/2010 A2 is rotational break-up.
Astronomers photographed a suspected asteroid-to-asteroid collision for the first time. This time-lapse video of Hubble telescope images shows the smashed-up remnants in the Asteroid Belt thinning out over the course of 5 months.