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

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) West Animation of three 10sec exps Tail 1 arcmin long 2004 Mar m reflector Siding Spring Observatory R. H. McNaught North q = AU e = i = 21.2 deg a = 2.96 (P = 5.09 yrs)

Meteor Shower Jenniskens (2006) 1 st 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

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

True RADIANT RA 122 +/- 1d Dec +79 +/- 1d (Ye and Wiegert) km/s (Maslov,Asher) (Vaubaillon) (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.

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

Asher’s dust trails Note: profile through Ye’s plot has peak after the dust trails 20-rev21-rev 22-rev 23-rev rev 46-rev 47-rev rev

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

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 (r E -r D )

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

Asher’s dust trails Dust trails <20-rev old have large r E -r D 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

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. Asher’s dust trails

Year Mo Da UT Revs  a 0 r E -r D f M : : : : : : : : : : : : : : : : : : : : : : : Revs – number of orbits of dust from ejection to 2014  a 0 –difference between semi-major axis (a 0 ) of the comet and the particle at ejection.  a 0 ~0.0 => large particles r E -r D – distance of the dust trail node from Earth’s orbit. (Earth radius= AU) f M – estimate of dispersion of the trail since ejection (at ejection f M =1.000)

Asher’s dust trails Year Mo Da UT Revs  a 0 r E -r D f M : : : : : : : : : : Revs – number of orbits of dust from ejection to 2014  a 0 –difference between semi-major axis (a 0 ) of the comet and the particle at ejection.  a 0 ~0.0 => large particles r E -r D – distance of the dust trail node from Earth’s orbit. (Earth radius= AU) f M – estimate of dispersion of the trail since ejection (at ejection f M =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.

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

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= from comet’s current activity Differences in peak (06:29-07:40UT) and duration (FWHM~0.4 day to rather less)

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

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

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 Conclusion

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