ISON split? Or fragment as it dive bombs the sun?

There has been a lot of things to develop in last 48 hours as ISON reaches perihelion.

Best image site for ISON.
iSON real time images

the most recent images



ISON tracking tool part 2.

I posted one from TIME earlier this week.

ISON tracker

The accusations it split

H. Boehnhardt, C. Tubiana, N. Oklay, and J. B. Vincent, Max Planck Institute for Solar System Research, Katlenburg-Lindau; and U. Hopp, C. Ries, M. Schmidt, A. Riffeser, and C. Goessl, Astronomical Institute, Ludwig Maximilian University, Munich, report the detection of coma wings in Laplace-filter-processed CCD exposures of comet C/2012 S1 obtained with the 0.4-m telescope of the Mt. Wendelstein Observatory on Nov. 14.16-14.21 and 16.16-16.21 UT. The arclet-like wings appeared in opposite direction from the nucleus at position angles 15 and 195 deg on Nov. 14 and at p.a. 25 and 205 deg on Nov. 16. The coma wings extended straight from the nucleus for about 4700 km on Nov. 14 and 13500 km on Nov. 16 on either side of the extended radius vector and continued in streamers of the plasma tail. No coma wings were found in similar exposures obtained on Nov. 13. The coma wings suggest the presence of two or more sub-nuclei with individual expanding atmospheres in the overall cometary coma and may indicate recent nucleus splitting in the comet.

link to data

YouTube vid

YouTube vid



NASA Comet ISON observing campaign

Personally I think the best website to keep watch on valid scientific observations

There is some discussion over a report that has been made in which the authors describe “ coma wings [that] suggest the presence of two or more sub-nuclei” in Laplacian-filtered comet ISON images. This is a report that has been made by some respected scientists, and thus the CIOC team are definitely taking the report seriously. Indeed, as we have commented, comet ISON’s recent dramatic outburst could absolutely be the result of fragmentation of its nucleus. However, it could equally likely be the result of the expect increase in activity as it continues to approach the Sun. Both of these are possibilities that we have outlined out on this site.

We encourage more observations and analysis, but do urge caution with this latest report. The “wings” that the authors describe certainly could be the result of fragmentation, as so-called arclets are indeed correlated with fragmentation events. However, other possibilities exist:
1. Their appearance is remarkably symmetrical, which leads us to be a little more skeptical that they could be the result of a fragmentation. Fragmentation of cometary nuclei is typically an asymmetrical event, often with fragments trailing in the comet’s tail, as was the case with 73P/Schwassmann–Wachmann and C/1996 B2 (Hyakutake), for example.
2. Prior to this outburst, several so-called “jets” had been reported in the area of activity that seems to be the source of these wings and thus it is possible that we are seeing enhanced dust emission due to jets in ISON’s nucleus.
3. We could simply be seeing solar wind ion tail structures, perhaps after some solar wind interaction event, for example with a coronal mass ejection or a co-rotating interaction region, or some other solar wind density enhancement. Indeed, spacecraft observations certainly indicate such interactions to have happened (this will be the source of a bog post later this week), but whether or not that interaction caused this new feature is still unknown.
The CIOC Team supports and encourages reports such as this, and we certainly monitor them closely. Our motivation for this blog post is to urge this discussion to continue, and we strongly encourage further data analysis efforts and a community-wide sharing of information on this and related subjects.

For now we continue to monitor the situation, to see which one of these scenarios is occurring. If the comet has fragmented, we should see some dramatic changes in the next few days. Typically we expect a large increase in brightness followed then by a dramatic decrease in the comet’s brightness in these situations. If instead jets are the cause, we expect the “wings” to persist and grow. If the behavior is driven by the solar wind then we should see continual changes as the solar wind changes. This is monitored by a number of spacecraft 24/7 and reliable solar wind models, so should be possible to verify.


Keep your eyes up. How can you not think this is fascinating and a once in lifetime opportunity.



2 thoughts on “ISON split? Or fragment as it dive bombs the sun?

  1. Its like you read my mind! You appear to know a lot about this, like you
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