A joint team of astronomers from the USA and Germany presented a study where they analyzed an unusual comet P/2013 P5. This object orbits within the main asteroid belt and its most prominent feature is that it has in total six tails made of space dust. The paper outlining the results of the study has been recently published at arXiv.org.

The astronomers analyzed data acquired by the Hubble Space Telescope. P/2013 P5 has been spotted on August 27, 2013. Interestingly enough, this celestial body has an asteroid-like orbit, although its appearance is more similar to a typical comet, so the authors of the paper classified P/2013 P5 as an active asteroid, or the main-belt comet (MBC).

The astronomers made two separate observations on September 10 and 23, 2013, using WFC3 camera to determine the basic properties and characteristics of P/2013 P5 and obtained 12 unique images of the comet. Five exposures of 348 seconds and one of 233 seconds were obtained during each observation. Later these images were combined for separate observation orbits.

The composite images for both observation dates clearly showed a structured, multiple tail system of P/2013 P5. The team noted that the differences in morphological features of those images were dramatic despite a relatively short (approximately two-week-long) interval between observation dates employed for this study. Both images contain a centrally condensed nucleus (marked as N in the image), although most of the other features have changed in both brightness and position, so it is difficult to make correlations between these observations. The tails of the object are marked as A-F in both panels of the image above.

The study also states that comet Tail A changed the least between the observations, considering its direction, length and brightness. Differences between position angle and and projected orbital velocity vector allow to suggest that Tail A may contain larger, slower and probably older particles compared to other tails. Tails B, C and D became wider and faded in surface brightness. Meanwhile, Tail E has grown in length and brightness between two observations, indicating that fresh material is currently being fed into the P/2013 P5.

The team concludes that it is unlikely for P/2013 P5 to be a comet captured from the Kuiper belt or Oort cloud comet reservoirs, as numerical simulations performed more than a decade ago have already dismissed a possibility for such an event to happen in a modern Solar system. Another assumption is that a potential source of dust could have originated due to some impact in the asteroid belt, although this theory could not be supported by the observed spread and fading characteristics of the tails.

According to the authors, the remaining and most viable hypothesis is that P/2013 P5 generates the trail of dust due to the rotational mass-shedding, presumably from torques imposed by solar radiation. However, this assumption should be verified by additional numerical simulations.

By Alius Noreika, Source: Technology.org