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

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)

We

st

Animation of three 10sec expsTail 1 arcmin long2004 Mar 301.0-m reflectorSiding Spring ObservatoryR. H. McNaught

North

q = 0.969 AUe = 0.672i = 21.2 dega = 2.96 (P = 5.09 yrs)

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

209P meteor shower

DaylightNight

Galapagos

Hawaii

Fiji

Samoa

Observedradiantelevation

200

400

00

2014 May 2407:00UT

True RADIANT

• RA 122 +/- 1d Dec +79 +/- 1d (Ye and Wiegert)

• 122.8 +79.1 19.6km/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.

Nearbydust trails

2014 EncounterVery consistent with the dust trails, but saturation of this plotallows no interpretation of the shower profile or peak time.

Vaubaillon

Asher’s dust trails

Note: profile through Ye and Wiegert’s plot has peak after the dust trails

20-rev21-rev

22-rev

23-rev

24-45-rev

46-rev

47-rev

48-52-rev

Dust trails with|rE-rD|>0.0200AUare not plotted, buthigh densityregion is confirmedby 1 to 16-rev trails

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

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

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

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

Earth at node, time = T1

Dust trail theory

Earth’s orbit

Particle orbit

Node

Particle at time = T0

Particle at time = T1

Particle at time = Tfinal

To Sun

Modified particle orbit

Final particle orbit

Earth at node, time = T0

(Initial P too short)

(Initial P too long)

(Initial P correct)

Earth at node, time = Tfinal

rE-rD

rE = distance of Earth from SunrD = distance of dust trail from Sun

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

• 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 209P dust trails

Year Mo Da UT Revs a0 rE-rD fM

2014 5 24 08:00 20 0.002 0.00202 -0.2292014 5 24 07:24 21 0.001 0.00061 -0.1492014 5 24 07:09 22 0.001 0.00005 -0.1132014 5 24 07:01 23 0.001 -0.00025 -0.0952014 5 24 06:55 24 0.001 -0.00044 -0.0822014 5 24 06:52 25 0.000 -0.00057 -0.0742014 5 24 06:48 26 0.000 -0.00067 -0.0672014 5 24 06:45 27 0.000 -0.00079 -0.0502014 5 24 06:42 28 0.000 -0.00086 -0.0402014 5 24 06:39 29 0.000 -0.00090 -0.0332014 5 24 06:38 30 0.000 -0.00093 -0.0292014 5 24 06:37 31 0.000 -0.00095 -0.0262014 5 24 06:37 32 0.000 -0.00096 -0.0202014 5 24 06:35 33 0.000 -0.00097 -0.0212014 5 24 06:34 34 0.000 -0.00097 -0.0222014 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

Revs – number of orbits of dust from ejection to 2014

a0 – difference betweensemi-major axis (a0) ofthe comet and the

particle at ejection. a0~0.0 => 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

Asher’s 209P dust trails

Asher’s 209P dust trailsYear Mo Da UT Revs a0 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.

Revs – number of orbits of dust from ejection to 2014

a0 – difference betweensemi-major axis (a0) ofthe comet and the

particle at ejection. a0~0.0 => 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

A time = Tx,(a short time before theencounter, but with the particlessufficiently far from the Earth for theparticle’s orbit to be essentiallyunperturbed by the Earth),predict the position of threeparticles that differed at thislocation after 1-rev by a tinyamount, dM0, in their mean anomaly.

Calculating fM

Earth’s orbit

Particle orbit

Particle 0 at time = Tx (Nominal dust trail)

Particle 1 at time = Tx

Particle 2 at time = Tx

dMx(2)

dMx(1)

dM0

The extent of theincrease 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 significantlyfrom dMx(2), this indicates asignificant non-linearity in the dusttrail stretching, as a result of perturbations.

Calculating fM

Earth’s orbit

Particle orbit

Particle 0 at time = Tx (Nominal dust trail)

Particle 1 at time = Tx

Particle 2 at time = Tx

dMx(2)

dMx(1)

dM0

Calculating fM

Earth’s orbit

Particle orbit

Particle 0 at time = Tx (Nominal dust trail)

Particle 1 at time = Tx

Particle 2 at time = Tx

dMx(2)

dMx(1)

dM0

Asher uses more particles for this parameter and checks uniformityas well as the level of stretching.

Non-uniform distributionindicates perturbations andunreliability of the fM value.

-ve values of fM indicate that the trailhas bent backwards on itself.

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.

Shower profile

Ye and Wiegert

(08:15UT)

(06:29UT)Asher’s dust trailssuggest a similarbut narrower spreadcomprising 2 peaks.

Ap

pro

xim

ate

s to

ZH

R

Average fluenceshould be unaffectedby binning but peakrates and widthprobably are.

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)

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

Correction to Peak times

Daylight

Night

2014 May 2407:00UT Galapagos

Hawaii

Fiji

Samoa

• 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

Conclusion

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