Meteors from 209P/LINEAR

1. Meteors from 209P/LINEAR A Summary by Rob McNaught, based on simulations by David Asher Expanded and amended (May 20) from a presentation to the TA meeting 2014 May 10, Basingstoke

2. 209P/LINEAR • 2004 Feb 03 - NEA 2004 CB discovered by LINEAR (MPEC 2004-C16) • 2004 Mar 30 - Found to be a comet by Rob McNaught (IAUC 8314) North q = 0.969 AU e = 0.672 i = 21.2 deg a = 2.96 (P = 5.09 yrs) West Animation of three 10sec exps Tail 1 arcmin long 2004 Mar 30 1.0-m reflector Siding Spring Observatory R. H. McNaught

3. Meteor Shower • Jenniskens (2004) 1st to note possibility • Lyytinen/Jenniskens (2006) made dust trail calculations • Vaubaillon (2012) used supercomputer to calculate millions of particle motions • Maslov (2013) made dust trail calculations • Ye and Wiegert (2013) modelled dust tail of 209P and particle stream • Asher (2014) made dust trail calculations • All indicate a shower over N America

4. 209P meteor shower 2014 May 24 07:00UT Galapagos Observed radiant elevation 00 200 400 Night Daylight Hawaii Samoa Fiji

5. True RADIANT • RA 122+/-1d Dec +79 +/- 1d (Ye and Wiegert) • 122.8 +79.1 19.6km/s (Maslov,Asher) (J2000) Atmospheric velocity – very slow meteors The observed (apparent) radiant will be higher in the sky due to the gravitational bending of the incoming meteors by the Earth (to a max. of 11 deg). This is called Zenithal Attraction. (Vaubaillon)

6. 2014 Encounter Very consistent with the dust trails, but saturation of this plot allows no interpretation of the shower profile or peak time. Nearby dust trails Vaubaillon

7. Asher’s dust trails Dust trails with |rE-rD|>0.0200AU are not plotted, but high density region is confirmed by 1 to 16-rev trails 21-rev 20-rev 22-rev 23-rev 48-52-rev 24-45-rev 46-rev 47-rev Note: profile through Ye and Wiegert’s plot has peak after the dust trails

8. Dust trails and binning • The modern variant of dust trail calculations developed following limitations of some Leonid research that used significant binning • Asher’s dust trail calculations for both the Leonids and 209P indicate that unperturbed dust trails retain their profile between returns • However, they can shift significantly in nodal distance and longitude over +/- 1day • Binning is not wrong, it’s just less precise

9. Dust trails and binning • Binning +/- 7 days will diffuse the reality of what is happening at the instant of the nodal encounter • Dust trail calculations are much simpler to do and detail precisely where the core of a dust trail is at the instant it crosses the node • If the trail is wide enough, it will produce meteors at that instant

10. Dust trail theory • Developed by Miroslav Plavec in 50s • Demonstrated successfully by Reznikov, Kondrat'eva and colleagues in 80sand 90s for many streams • Rediscovered several times

11. Dust trail theory • Start with ejection at prior perihelion • Alter orbital period to estimate particle arrival at node at same time as Earth in 2014 • Perturbations change this arrival time • Iterate the starting period to produce arrival at node at exactly the instant the Earth is at that same solar longitude. • Note the distance (rE-rD) of the particle from the Earth

12. Dust trail theory Modified particle orbit Final particle orbit Particle at time = T1 Particle orbit (Initial P too long) Node Earth’s orbit Particle at time = Tfinal rE-rD (Initial P correct) Particle at time = T0 Earth at node, time = T1 Earth at node, time = T0 Earth at node, time = Tfinal (Initial P too short) rE = distance of Earth from Sun rD = distance of dust trail from Sun To Sun

13. Asher’s 209P dust trails • Dust trails <20-rev old have large rE-rD i.e. too distant for meteors, but lie mostly in the Ye and Wiegert highest density zone • The 22 and 47-rev trails have ~direct hits • Trails between 27 and 45-revs are almost coincident, but offset from the Earth’s orbit • Dust trails >52-rev old are still in the Earth’s vicinity, but strongly disrupted and not well suited for dust trail prediction

14. Asher’s 209P dust trails • The trails align across the Earth’s orbit almost perpendicularly, so peak at similar times (Leonid trails were more scattered). • The first trails to be encountered are older, then younger and finally much older. • Dust trail calculations are based on the centre of the Earth. A time adjustment is needed for when a specific location passes through the dust sheet.

15. Asher’s 209P dust trails Revs – number of orbits of dust from ejection to 2014 Da0 – difference between semi-major axis (a0) of the comet and the particle at ejection. Da0~0.0 => large particles rE-rD – distance of the dust trail node from Earth’s orbit. (Earth radius =0.00004AU) (Impact radius=0.00005AU) fM – estimate of the along-trail dispersion. For a 1-rev trail, fM= 1.0, but for an unperturbed n-rev trail, fM= 1/n Year Mo Da UT Revs Da0 rE-rD fM 2014 5 24 08:00 20 0.002 0.00202 -0.229 2014 5 24 07:24 21 0.001 0.00061 -0.149 2014 5 24 07:09 22 0.001 0.00005 -0.113 2014 5 24 07:01 23 0.001 -0.00025 -0.095 2014 5 24 06:55 24 0.001 -0.00044 -0.082 2014 5 24 06:52 25 0.000 -0.00057 -0.074 2014 5 24 06:48 26 0.000 -0.00067 -0.067 2014 5 24 06:45 27 0.000 -0.00079 -0.050 2014 5 24 06:42 28 0.000 -0.00086 -0.040 2014 5 24 06:39 29 0.000 -0.00090 -0.033 2014 5 24 06:38 30 0.000 -0.00093 -0.029 2014 5 24 06:37 31 0.000 -0.00095 -0.026 2014 5 24 06:37 32 0.000 -0.00096 -0.020 2014 5 24 06:35 33 0.000 -0.00097 -0.021 2014 5 24 06:34 34 0.000 -0.00097 -0.022 2014 5 24 06:34 35 0.000 -0.00099 -.--- 2014 5 24 06:34 36 0.000 -0.00100 -.--- 2014 5 24 06:34 37 0.000 -0.00101 -.--- 2014 5 24 06:34 38 0.000 -0.00102 -.--- 2014 5 24 06:34 39 0.000 -0.00102 -.--- 2014 5 24 06:34 40 0.000 -0.00101 -.--- 2014 5 24 06:34 41 0.000 -0.00101 -.--- 2014 5 24 06:38 42 0.000 -0.00099 -0.017

16. Asher’s 209P dust trails Revs – number of orbits of dust from ejection to 2014 Da0 – difference between semi-major axis (a0) of the comet and the particle at ejection. Da0~0.0 => large particles rE-rD – distance of the dust trail node from Earth’s orbit. (Earth radius =0.00004AU) (Impact radius=0.00005AU) fM – estimate of the along-trail dispersion. For a 1-rev trail, fM= 1.0 but for an unperturbed n-rev trail, fM= 1/n Year Mo Da UT Revs Da0 rE-rD fM 2014 5 24 06:37 43 0.000 -0.00096 -0.0232014 5 24 06:39 44 0.000 -0.00091 -0.0312014 5 24 06:47 45 0.000 -0.00078 -0.0542014 5 24 07:14 46 0.001 -0.00043 -0.1162014 5 24 07:47 47 0.001 0.00001 -0.0472014 5 24 08:02 48 0.001 0.00019 -.---2014 5 24 08:09 49 0.001 0.00030 -.---2014 5 24 08:14 50 0.001 0.00038 -.---2014 5 24 08:19 51 0.001 0.00046 -.---2014 5 24 08:22 52 0.001 0.00054 -.--- The 46-rev trail would combine with the main 22-rev peak. The 47-rev trail will be a direct hit but this and older trails are encountered much later. This should give a second lower peak with a slow tail off.

17. Calculating fM Particle orbit Particle 2 at time = Tx dM0 Particle 0 at time = Tx (Nominal dust trail) dMx(2) Particle 1 at time = Tx dMx(1) A time = Tx, (a short time before the encounter, but with the particles sufficiently far from the Earth for the particle’s orbit to be essentially unperturbed by the Earth), predict the position of three particles that differed at this location after 1-rev by a tiny amount, dM0, in their mean anomaly. Earth’s orbit

18. Calculating fM Particle orbit Particle 2 at time = Tx dM0 Particle 0 at time = Tx (Nominal dust trail) dMx(2) Particle 1 at time = Tx dMx(1) The extent of the increase of dMx(1) and dMx(2) over dM0 indicates the dilution of the dust trail density by stretching, fM = 2*dM0/(dMx(1)+dMx(2)) If dMx(1) differs significantly from dMx(2), this indicates a significant non-linearity in the dust trail stretching, as a result of perturbations. Earth’s orbit

19. Calculating fM Particle orbit Particle 2 at time = Tx dM0 Particle 0 at time = Tx (Nominal dust trail) dMx(2) Particle 1 at time = Tx dMx(1) Asher uses more particles for this parameter and checks uniformity as well as the level of stretching. Non-uniform distribution indicates perturbations and unreliability of the fM value. -ve values of fM indicate that the trail has bent backwards on itself. Earth’s orbit

20. da0 and particle size • For 3mm particles of typical density, solar radiation pressure ratio, beta=0.0001. • beta=0.0001 would be the equivalent of a tangential ejection velocity from 209P of 2m/s & da0=0.0016 • Period is key as particles with same period roughly comove in space, experiencing similar perturbations • For most of the dust trail encounters, da0<0.001. Particles in such orbits would have low beta and/or low ejection velocity, implying large particles and bright meteors.

21. Shower profile Average fluence should be unaffected by binning but peak rates and width probably are. (06:29UT) Asher’s dust trails suggest a similar but narrower spread comprising 2 peaks. Approximates to ZHR (08:15UT) Ye and Wiegert

22. What will happen? • All studies suggest the encountered particles will be large – bright meteors • Rates are very uncertain, as nothing is known of the comet’s historical activity. Rates will be ZHR=0 to storm! Estimated ZHR=200-400 from comet’s current activity • Differences in peak (06:29-07:40UT) and duration (FWHM~0.4 day to rather less)

23. When is the peak? • Ye and Wiegert - 06:29UT (modelling) • Lyytinen - 07:00UT (dust trail) • Asher (1st peak) - 07:09UT (dust trail) • Maslov - 07:21UT (dust trail) • Vaubaillon - 07:40UT (modelling) • Asher (2nd peak) - 07:47UT (dust trail) • Predictions are for the Earth’s centre. Peak will be 8 mins earlier from N America

24. Correction to Peak times 2014 May 24 07:00UT Galapagos Night Hawaii Daylight Samoa Fiji

25. Conclusion • Ye and Wiegert have probably too large a bin size which diffuses the reality • I trust Asher’s dust trail timings • Main peak centred around the 22-rev trail at 07:09UT (unadjusted), superimposed on a broader shower with slow rise and sharper fall off • A lower peak from the 47-rev trail at 07:47UT (unadjusted) should have a sharp rise and slower decline

26. Finally • Staying in the UK? Don’t let daylight ruin a good shower • Core of the 22-rev dust trail will pass the daylight side of the Earth • Should fireballs occur, they will be visible if the sky is clear • Peaks at 07:00UT & 07:38UT (adjusted) for central UK, the apparent radiant will be at: Az=10 deg Alt=50 deg