What Next for the CIOC?

Apologies for going a tad quiet for a few days. The perihelion week for comet ISON was just ridiculously busy, and a short day for me was 12 full hours, so I needed to back off for a couple of days to try and catch my breath and prepare for the data analysis phase, and continue to respond to media enquiries, etc. We have a few things going on next so here's a quick summary.

Right now, we are having a post-perihelion comet ISON meeting where we are discussing the status of the comet, the observations and data recorded, and possible future plans for the comet. We livestreamed the first part of the meeting, and the videos from Session 1 and Session 2 are already available online for replay. I do want to mention something about the afternoon session though, as we have received some criticism and complaints for not livestreaming the discussions of the science results from many of the ground and space-based observatories.

In the morning session, we gave an overview of the comet, amateur observing programs, and space-based observations. This was really just a summary of the info we've all known for a few days now. The afternoon session is where scientists begin to present their results from their observing of ISON and we chose not to stream these, partly at the request of the scientists. There's a really good reason too: the stuff being presented in the afternoon session is fresh, new, raw data, and the results are preliminary and unverified. As scientists, we all understand the implications of this and so we listen to the results with open ears and minds, but we realize that conclusions are preliminary and that no results are to be assumed absolute fact until they have been passed through the peer review process. The public is not used to this, and nor do we expect them to be so, and it would be very easy to draw mistaken conclusions from much of the discussion occurring.

It is critical in science that when a result is made public, it is done so with an extremely high degree of confidence. This is a fundamental part of the scientific process and not one where we can compromise. We're tossing ideas around among ourselves so that we can understand what's going on, and then we release the results. It's not about distrust of the public, we promise - we just don't want to give out bad results!

Moving on... I trust most people are aware of what happened to comet ISON at perihelion, but I'll recap: As ISON approached the Sun, it flared rapidly in brightness until about 12-hours before closest approach. Following that, it began to fade quite rapidly, and appeared to lose any clear indication of a nucleus. Something of the comet did emerge from the Sun's outer atmosphere,but it was a dusty, diffuse streak, again with no apparent nucleus. In the following days, the resulting dust cloud drifted away from the Sun, becoming increasingly faint and diffuse. As of the most recent STEREO data that I've looked at, comet ISON is really quite difficult to detect and certainly no central condensation (i.e. bright spot, or nucleus) is visible.

We have heard results that around perihelion, ISON appeared to stop producing so-called "Lyman-Alpha photons", based on results we've seen in instruments on the ESA/NASA SOHO satellite. Without getting technical, Lyman-Alpha is a consequence of sunlight interacting with hydrogen, and if we are not seeing that interaction then it means that the levels of hydrogen (and hence ice) are extremely low. This is indicative of a completely burned out nucleus, or no nucleus at all.

The evidence appears strong that at some point approaching perihelion - whether days or hours - comet ISON likely began to completely fall apart, quite possibly much like comet C/1999 S4 (LINEAR) which fell apart into a bunch of pieces, and was imaged in detail by several telescopes. What remains of ISON now is going to be either just a cloud of dust, or perhaps a few very depleted chunks of nucleus. Either way, it's not going to flare up at this point and we should assume the comet's show is over.

However, we do need to verify this, and hopefully the Hubble team can come to the rescue! In mid-December, Hubble will be pointed in the direction of where ISON should be and they'll try and image something. If no fragments are surviving, or they are tiny, then Hubble will not be able to find anything, but that negative detection will tell us something: namely that ISON is indeed gone for good.

Next week I'll be at the American Geophysical Union Meeting in San Francisco, where we'll be having a session discussing comet ISON, and I will be part of a NASA Media Press Conference about the comet. I'm sure that there will be some interesting results announced and discussed at the meeting next week, so I'll report back on those as-and-when I can. I will be busy though, so the blog drought might drag on a little more yet...

Keep up-to-date on the latest ISON and sungrazing comet news via my @SungrazerComets Twitter feed. All opinions stated on there, and in these blog posts, are my own, and not necessarily those of NASA or the Naval Research Lab.