The tiny comet 209P/LINEAR and its associated Camelopardalid meteor shower (which may produce an outburst on May 24, less than two weeks from now) are getting attentions, and it seems that people start talking about my earlier work with Prof. Paul Wiegert that made prediction of this new meteor shower — hmm, not bad for a first year PhD, I guess!
However, I saw people quoting the number of ZHR=200 appeared somewhere in the paper (for example, Sky & Telescope and EarthSky), perhaps our wording in the paper was too cautious and I find the need to clarify. Indeed, we stated “a predicted ZHR of about 200 for our nominal scenario” (p. 3286 just under Fig. 3), but to my understanding of how Paul construct his model, this “nominal scenario” actually means that “209P/LINEAR is a kind-of nominal comet”, like those parent bodies of well-known and predicted meteor showers, such as 21P/Giacobini-Zinner (which is really what my Master’s thesis is about, by the way) or 55P/Tempel-Tuttle. Since our analyse seem to show that the dust/gas activity of 209P/LINEAR seems to be 1-2 magnitude lower than a “nominal comet” at its size, the “true” ZHR of the meteor shower may also be 1-2 magnitude lower, so I incline to expect a ZHR around 10-ish.
In the paper, we also showed that the cometary tail as imaged in 2009 was dominated by large, millimeter-sized particles, and numerical simulation suggested that particles at this size are likely to dominate the May 24 outburst, which may suggest that the outburst event “may be dominated by bright meteors”. Well, darn, I should have used terms like “above-average brightness” — as the Camelopardalid meteoroids are exceptionally slow when arrive the Earth (about 16 km/s). Assuming a density of 1000 kg/m^3, a millimeter-sized particle is about 0.01 g. If we use the figure below for a conversion, we see that a millimeter-sized Camelopardalid meteoroid corresponds to a +6 magnitude meteor! (meteor’s absolute magnitude: the magnitude of the meteor as seen by the observer when the meteor is placed at a height of 100 km at zenith direction from the observer)
Hmm, sounds not very encouraging. But I will be more than happy to find out if I am wrong. In fact, the uncertainty is so large that we literally won’t know what we will see until we see it. For example, as the event is caused by the material released by 209P/LINEAR about two century ago, the comet could well have been more active at that time — or it could be the remnant of a recent catastrophic event which would mean that a large amount of meteoroids have been deposit in the orbit. This is why we need meteor observation, it is like a time machine and can tell us some information about the parent body in its past.
An interesting point I noticed is that at least two groups (Rudawska & Jenniskens 2013, Meteoroids, and Segon et al. 2014, JIMO 42) reported that they found a weak annual meteor shower in May while examining their own video data that may be linked to 209P/LINEAR. However, both groups reported a slightly earlier date (Rudawska & Jenniskens reported April 22 to May 6, Segon et al. reported April 24 to June 4 and peaked on May 12). If this linkage is real, then it implied that 209P/LINEAR was releasing more material possibly several centuries ago, as it takes time for the material to distribute around the orbit and shift from the parent body. From the perspective of dynamics, it is very difficult to chase the comet back to before ~1800s, as the comet makes frequent close approach to Jupiter that alters its orbit.
In any case, I will keep my eyes on this event. After the excitement of the last Leonids return in 1998-2002 (which produced three meteor storms and officially marked my involvement to meteor science!), it seems we need to wait quite a bit (maybe a few decades) for the next meteor storm, so I feel lucky to be able to involve in a meteor outburst prediction… and I am eager to find out the result. I have placed quite a bit of side projects around it as I also got time on Gemini for cometary spectra and is working with my friends for some very deep exposures of the comet, I may write a bit about those later — just let me figure out how to work with IRAF…