Update on 209P/LINEAR and Camelopardalids

209P/LINEAR on Apr 9.25 (UT) by Gemini North + GMOS, the image is approximately 50"x30". (Quan-Zhi Ye/Gemini Observatory)

209P/LINEAR on Apr 9.25 (UT) by Gemini North + GMOS, the image is approximately 50″x30″. North is up (Quan-Zhi Ye/Gemini Observatory)

Syndyne-synchrone modeling of the Gemini image, courtesy of Man-To Hui

Syndyne-synchrone modeling of the Gemini image, courtesy of Man-To Hui (UCLA)

A bit more news on 209P/LINEAR and the forthcoming Camelopardalid meteor shower:

  • Carl Hergenrother (U Arizona) reported his broad-band photometry of P/LINEAR in CBET 3870. His analysis indicated a slow rotator (best fit ~21.86 hr) and a larger-than-expected nucleus (at least 2 km). He also suggested that the comet is only active within 1.4 AU from the Sun.
  • There have been a few reports on meteorobs mailing list and noted by the American Meteor Society about some fireballs that looks like Camelopardalid member (northern radiant + slow). I remain skeptical until I see the orbit.
  • Peter Jenniskens (SETI) is hosting a great website here and keeping collecting information about P/LINEAR and Camelopardalids. On the post of May 20 he noted the higher chance of seeing lunar meteoroid impacts as calculated by Peter Zimnikoval. The predicted peak time for the moon is about 4h UT on May 24.
  • On the same date, Jenniskens also wrote that he and his colleagues detected an annual meteor shower called sigma Ursae Majorids in the CAMS network that appears in mid June. Note that this is actually reported in a submitted paper and he did not note the registered Camelopardalid meteor shower (code 451; this may or may not be the same Camelopardalid meteor shower we used to refer the forthcoming outburst) he mentioned in his earlier study (Rudawska & Jennsikens 2014). It is not clear to me why is this — for example, if these two meteor showers are in fact the same one.
  • Jenniskens also reported the measurement by David Schleicher (Lowell) which showed an extremely low activity of P/LINEAR (CBET pending).

For me, I have been trying to learn IRAF to reduce my spectra taken with Gemini in early April at the breaks of my thesis project. Well, I managed to do it at last (mind you, that was an EUREKA moment!), but I am yet to refine it (combining more frames, etc). Initial measurement of cometary emission species of CN, C_2 and C_3 (upper limit is <~10**25 mol/s) agree with David’s suggestion and the conclusion of our earlier study that P/LINEAR seems to be very depleted in dust production. Meanwhile, I also check the daily log of CAMO and I do not see any activity pops up in either optical system or the radar.

Today Apostolos Christou from Armagh Observatory visited our group and brought us a surprise — a fresh-new prediction by David Asher and Robert McNaught (I first learnt the two’s names when I was in grade 6 in primary school when preparing for the Leonids 1999 return). Their prediction kinds of aligned with me and Paul’s prediction, although their timing is more inclined to other predictions (peaks around 7h UT) and their predicted FWHM is shorter (~40 min). They also thought that materials older than 52-rev (~1800) is likely heavily perturbed and is difficult to predict. I talk to Apostolos and Paul about the idea of resonance enhancements (i.e. certain kinds of orbit setups that can reduce the effect of perturbation and preserve strong enhancements within the trail, see the strong and unexpected outburst in 1998 Leonids). They thought that perhaps nobody has taken a closer look into this (Paul said he didn’t), so we probably won’t know until we see it. Keep in mind that surprise can happen!

After all, my thought: we will know in 48 hours. I still think that the activity due to the calculated trails (1800-1900s) will likely be weak (ZHR~10-ish, maybe) and faint (rich in +5 magnitude, maybe) unless we are really lucky (e.g. P/LINEAR is the remnant of a recent catastrophic event or similar things like that). Materials older than 52-rev may have a shoot there, too. My advisor, Peter Brown, also noted that any meteorite-dropper will have to be at least kg-sized, and I don’t see how can an extincting comet do that. But surely we never know…

Some thoughts on the forthcoming Camelopardalid meteor shower

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)

The relation between meteor's brightness and its arrival speed (M. Campbell-Brown and P. Brown)

The relation between meteor’s brightness and its arrival speed (M. Campbell-Brown and P. Brown)

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…