Meteors from 209P/LINEAR

1. Meteors from 209P/LINEAR A Summary by Rob McNaught TA meeting 2014 May 10

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 (2006) 1st to note possibility • Lyytinen made dust trail calculations • Vaubaillon used supercomputer to calculate millions of particle motions • Maslov made dust trail calculations • Ye and Wiegert (2013) modelled dust tail of 209P, used supercomputer for particles • Asher (2014) dust trail calculations • All indicate a shower over N America

4. 209P meteor shower For 07:00UT shift plot east by 7.5 deg Radiant 40o elevation Radiant on horizon Max radiant Elev = 58o Hawaii Shower visible in darkness Galapagos Fiji Samoa Night to nautical twilight Daylight to nautical twilight New Caledonia Radiant elevations corrected for zenithal attraction B. Berard, IMCCE

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 21-rev 20-rev 22-rev 23-rev 48-52-rev 24-45-rev 46-rev 47-rev Note: profile through Ye’s plot has peak after the dust trails

8. Asher’s dust trails • 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 centre 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

9. Asher’s dust trails • 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 of the particle from the Earth (rE-rD)

10. Asher’s dust trails Simplified diagram Particle orbit Initial P too long Node Earth’s orbit Initial P correct Assume initial orbital period (P) for particle and calculate its location in 2014 (time = T) rE-rD Earth at node, time = T Initial P too short rE = distance of Earth from Sun rD = distance of dust trail from Sun To Sun

11. Asher’s dust trails • Dust trails <20-rev old have large rE-rD i.e. too distant for meteors • The 22 and 47-rev trails have direct hits • Trails between 27 and 45-revs are almost coincident, but rather 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

12. Asher’s 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.

13. Asher’s dust trails Year Mo Da UT Revs Da0 rE-rD fM 2014 5 24 07:58 20 0.002 0.00200 -0.229 2014 5 24 07:22 21 0.001 0.00059 -0.149 2014 5 24 07:06 22 0.001 0.00003 -0.113 2014 5 24 06:59 23 0.001 -0.00027 -0.095 2014 5 24 06:53 24 0.001 -0.00046 -0.082 2014 5 24 06:50 25 0.000 -0.00059 -0.074 2014 5 24 06:46 26 0.000 -0.00069 -0.067 2014 5 24 06:43 27 0.000 -0.00081 -0.050 2014 5 24 06:40 28 0.000 -0.00088 -0.040 2014 5 24 06:37 29 0.000 -0.00092 -0.033 2014 5 24 06:36 30 0.000 -0.00095 -0.029 2014 5 24 06:35 31 0.000 -0.00097 -0.026 2014 5 24 06:35 32 0.000 -0.00098 -0.020 2014 5 24 06:33 33 0.000 -0.00099 -0.021 2014 5 24 06:32 34 0.000 -0.00099 -0.022 2014 5 24 06:32 35 0.000 -0.00101 -.--- 2014 5 24 06:32 36 0.000 -0.00102 -.--- 2014 5 24 06:32 37 0.000 -0.00103 -.--- 2014 5 24 06:32 38 0.000 -0.00104 -.--- 2014 5 24 06:32 39 0.000 -0.00104 -.--- 2014 5 24 06:32 40 0.000 -0.00103 -.--- 2014 5 24 06:32 41 0.000 -0.00103 -.--- 2014 5 24 06:36 42 0.000 -0.00101 -0.017 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) fM – estimate of dispersion of the trail since ejection (at ejection fM=1.000)

14. Asher’s dust trails Year Mo Da UT Revs Da0 rE-rD fM 2014 5 24 06:35 43 0.000 -0.00098 -0.0232014 5 24 06:37 44 0.000 -0.00093 -0.0312014 5 24 06:45 45 0.000 -0.00080 -0.0542014 5 24 07:12 46 0.001 -0.00045 -0.1162014 5 24 07:45 47 0.001 -0.00001 -0.0472014 5 24 08:00 48 0.001 0.00017 -.---2014 5 24 08:07 49 0.001 0.00028 -.---2014 5 24 08:12 50 0.001 0.00036 -.---2014 5 24 08:17 51 0.001 0.00044 -.---2014 5 24 08:20 52 0.001 0.00052 -.--- 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) fM – estimate of dispersion of the trail since ejection (at ejection fM=1.000) 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.

15. Shower profile For the reasons given, I believe this is too broad & inconsistent with their other plot. (06:29UT) Approximates to ZHR Asher’s dust trails indicate a similar but narrower spread comprising 2 peaks (08:15UT) Ye and Wiegert

16. 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)

17. When is the peak? • Ye and Wiegert - 06:29UT (modelling) • Lyytinen - 07:00UT (dust trail) • Asher (1st peak) - 07:06UT (dust trail) • Maslov - 07:21UT (dust trail) • Vaubaillon - 07:40UT (modelling) • Asher (2nd peak) - 07:45UT (dust trail) • Predictions are for the Earth’s centre. Peak will be 8 mins earlier from N America

18. Correction to Peak times -8 min -8 min -4 min -10 min -4 min +0 min Hawaii +0 min Shower visible in darkness +4 min +4 min Galapagos +8 min Fiji Samoa Night to nautical twilight Daylight to nautical twilight New Caledonia B. Berard, IMCCE

19. Conclusion • Ye and Wiegert have probably too large a bin size which diffuses the reality • I trust Asher’s dust trail calculations • Main peak centred around the 22-rev trail at 07:06UT (unadjusted), superimposed on a broader shower with slow rise and sharper fall off • A lower peak from the 47-rev trail at 07:45UT (unadjusted) should have a sharp rise and slower decline

20. Finally • Staying in the UK? Don’t let daylight ruin a good shower • Core of the 22-rev dust trail will intersect the daylight side of the Earth, e.g. UK • Should fireballs occur, they will be visible if the sky is clear • Peaks at 06:57UT & 07:36UT (adjusted) for central UK, the apparent radiant will be at: Az=10 deg Alt=51 deg