Median stack images of P/2016 G1 obtained with the OSIRIS instrument of the 10.4m GTC through a Sloan r′ filter, at the indicated dates. North is up, East to the left. The directions opposite to Sun and the negative of the orbital velocity motion are shown. The arrow in the middle of central panel indicates the westward feature that emerges from the inverted C-shaped mentioned in the text. The dimensions of the panels (from left to right, in km projected on the sky at the asteroid distance) are 27930×27930, 26305×26305, and 27025×27025. The images are stretched linearly in brightness, with maximum intensity levels, from left to right, of 8×10−14, 5×10−14, and 4×10−14 solar disk intensity units. Faint trailed stars are apparent near the head of the object, perpendicular to the tail, in the 8.91 June 2016 image, the brightest one being indicated by an arrow. Credit: Moreno et al.,2016
A team of Spanish astronomers has recently observed a newly discovered asteroid designated P/2016 G1 (PANSTARRS), revealing its activity and measuring its total dust loss. The findings detail the most probable hypothesis that could explain the cause of this activity. It was detected by R. Weryk and R. J. Wainscoat in April 2016 with 1.8-m Pan-STARRS1 telescope in Hawaii. With an asteroid-like orbit, having a semimajor axis of about 2.85 AU and an eccentricity of 0.21, this body exhibits transient, comet-like activity. Thus, the scientific community still argues whether objects like P/2016 G1 should be called “main-belt comets” (as they orbit the sun within the asteroid belt) or rather asteroids showcasing dust activity.
The real nature of these bodies could be revealed by detailed observations focusing on the processes taking place on their surfaces. For that reason, a team of researchers started observing P/2016 G1 shortly after its discovery. They used the 10.4m Gran Telescopio Canarias (GTC) at the Roque de los Muchachos Observatory in La Palma, Canary Islands to observe the asteroid during 3 nights from late April to June 8, 2016.
From GTC imaging data and Monte Carlo dust tail modeling, the team was able to get insights on the asteroid’s evolution and active processes. In particular, the model employed by the researchers computed the dust tail brightness of a comet or activated asteroid by adding up the contribution to the brightness of each particle ejected from the parent nucleus. According to the team’s observations and modeling, P/2016 G1 was activated about 350 days before perihelion (around Feb. 10, 2016). The activity had a duration of ~24 days and the total dust mass emitted from the asteroid was at least at a level of 17,000 tons.
This could be caused by various physical processes, including impact, thermal fracture, rotational instabilities and ice sublimation. However, due to the fact P/2016 G1 is located in the inner region of the main belt and has a small semi-major axis, the researchers excluded ice sublimation as the possible driver of this activity.
The most probable explanation for this activity is an impact event that would have induced a partial destruction of the asteroid, emitting dust grains to space nearly isotropically while the body is being torn apart. The impact itself had produced the ejection of some 240 tons of dust
The team also noted if the impact scenario is true, the smaller fragments of the parent body could exist in the vicinity of the asteroid’s dust cloud. However, deeper imaging of the object is needed to confirm this.
http://phys.org/news/2016-07-scientists-early-evolution-asteroid-p2016.htmljCp https://arxiv.org/abs/1607.03375
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