11institutetext:  Department of Physics and Astronomy, University of Western
Ontario, London, Ontario, N6A 3K7, Canada 22institutetext: Institute for Earth
and Space Exploration, University of Western Ontario, London, Ontario N6A 5B8,
Canada 33institutetext: Department of Geology, University of Otago, Dunedin,
New Zealand 44institutetext: Planétarium de Montréal, Espace pour la Vie, 4801
av. Pierre-de Coubertin, Montréal, Québec, Canada 55institutetext: IMCCE,
Observatoire de Paris - PSL, 77 av. Denfert-Rochereau 75014 Paris, France
66institutetext: Department of Astronomy, University of Maryland, College
Park, MD 20742, USA 77institutetext: Center for Space Physics, Boston
University, Boston, MA 02215, USA 88institutetext: Perth Observatory Volunteer
Group, Bickley, Western Australia 99institutetext: National Astronomical
Observatory of Japan, Tokyo, Japan 1010institutetext: NASA Meteoroid
Environment Office, Marshall Space Flight Center, Huntsville, AL 35812, USA

# Observations of the new meteor shower from comet 46P/Wirtanen

D. Vida , 1122<EMAIL_ADDRESS>J. M. Scott 33 A. Egal 441155 J. Vaubaillon 44
Q.-Z. Ye 6677 D. Rollinson 88 M. Sato 99 D. E. Moser 1010

(Received January 29, 2024; accepted February 6, 2024)

###### Abstract

Context. A new meteor shower $\lambda$-Sculptorids produced by the comet
46P/Wirtanen was forecast for December 12, 2023. The predicted activity was
highly uncertain, but generally considered to be low. Observations in
Australia, New Zealand, and Oceania were solicited to help constrain the size
distribution of meteoroids in the shower.

Aims. This work aims to characterize the new meteor shower, by comparing the
observed and predicted radiants and orbits, and to provide a calibration for
future predictions.

Methods. Global Meteor Network video cameras were used to observe the meteor
shower. Multi-station observations were used to compute trajectories and
orbits, while single-station observations were used to measure the flux
profile.

Results. A total of 23 $\lambda$-Sculptorid orbits have been measured. The
shower peaked at a zenithal hourly rate (ZHR) of $0.65^{+0.24}_{-0.20}$
meteors per hour at $\lambda_{\odot}=259.988^{\circ}\pm 0.042^{\circ}$. Due to
the low in-atmosphere speed of 15 km s-1, the mean mass of observed meteoroids
was 0.5 g ($\sim 10$ mm diameter), an order of magnitude higher than
predicted. The dynamical simulations of the meteoroid stream can only produce
such large meteoroids arriving at Earth in 2023 with correct radiants when a
very low meteoroid density of $\sim 100$ kg m-3 is assumed. However, this
assumption cannot reproduce the activity profile. It may be reproduced by
considering higher density meteoroids in a larger ecliptic plane-crossing time
window ($\Delta T$ = 20 days) and trails ejected prior to 1908, but then the
observed radiant structure is not reproduced.

###### Key Words.:

meteoroids – Comets: general – method: data analysis

##  1 Introduction

Before launch delays, the comet 46P/Wirtanen was initially selected as the
primary target for the Rosetta mission due to its favourable orbit and
interesting characteristics (Rickman & Jorda, 1998). At the time, the comet
was interesting as it had one of the largest nongravitational accelerations of
any comet that had undergone a recent orbital perturbation (i.e., close
approaches to Jupiter in 1972 and 1984), indicating a high fraction of
actively outgassing area (Schulz & Schwehm, 1999; Groussin & Lamy, 2003). The
comet had a very close approach to Earth in 2018, coming within 0.077 AU.
Moulane et al. (2023) performed observations using TRAPPIST telescopes and
found that the comet is “hyperactive,” with 40% of its surface active and
having the activity parameter $Af\rho(0)$ of 250 cm. In comparison, typical
Jupiter-family comets have active areas between 5-10 % (A’Hearn et al., 1995).
In a study relevant to this work, Coulson et al. (2020) found the possible
presence of mm-sized dust in the 46P’s coma, meaning that they could be
detected optically upon entering the atmosphere.

The comet’s orbit has a very low minimum orbit intersection distance (MOID) to
Earth of only 0.071 AU, which made it a target of investigation as a potential
meteor shower parent body (Ye & Jenniskens, 2022). Maslov & Muzyko (2017)
predicted possible low-activity outbursts in 2017 and 2019 with a zenithal
hourly rate (ZHR) not exceeding 5-10 meteors per hour. No positive
confirmations of the outbursts have been made in those years. Vaubaillon et
al. (2023) performed a separate set of simulations using five different
methods that mostly differ in terms of the conditions of meteoroid ejection
from the comet and in the modeling of non-gravitational forces during orbital
integration. The dynamical models by the co-authors are referred to in this
paper by their initials: AE (Egal et al., 2019), JV (Vaubaillon et al., 2005a,
b), QY (Ye et al., 2016), MS (Watanabe et al., 2005), and DM (Moser & Cooke,
2004, 2008)). All models roughly agreed and found no significant encounters of
ejected particles with the Earth in the past, except in 2007 and 2018 with the
1974 trail. A search on Canadian Meteor Orbit Radar (CMOR) data, which spans
over two decades (Brown et al., 2010) was performed for these years, as well
as the years predicted by Maslov & Muzyko (2017); however, no conclusive
detections have been found. However, due to the slow speed of meteoroids,
which severely impacts the ionization efficiency and the meteor shower
geocentric radiants being under the horizon, only a fraction of the largest
meteoroids could even be theoretically detectable due to zenithal attraction
(Gural, 2001).

For 2023, all five models of Vaubaillon et al. (2023) predict an encounter
with the 1974 trail ranging in time between December 12 08:23 UT and 20:06 UT.
In addition, the AE model predicts encounters with trails ejected between 1900
and 1945 a bit later, between December 12 at 17:05 UT and December 13 at 06:26
UT. Due to a lack of calibration on observations, only the upper limit on the
ZHR has been provided, estimated not to exceed ten meteors per hour on
average. The predicted distribution of geocentric radiants on the sky was
roughly diagonal and spanned about 15∘, from approximately R.A. = 10∘, Decl. =
-45∘ to R.A. = 6∘, Decl. = -33∘. The large extent of the radiant locations was
due to the uncertainty in encounter parameters and included all meteoroids
within 0.05 AU from Earth. However, meteoroids that were predicted to come the
closest, within 0.001 AU, were all concentrated in a tight 1∘ radius around
R.A. = 7.75∘, Decl. = -39∘. The radiant at the nominal peak time on December
12 at 10:15 UT was predicted to be in the zenith just off the southwestern tip
of Australia, located at the edge of the Earth’s terminator. The best
locations for optical observations were thus in Australia, New Zealand, and
the rest of the Southwest Pacific. The meteor shower was initially referred to
as the ”Wirtanenids,” but Vaubaillon et al. (2023) suggested a new name for
the shower, $\lambda$-Sculptorids, which has been accepted by the
International Astronomical Union (IAU) for the name of the shower and this
term is used herein to refer to the shower. The provisional designation for
the shower by the IAU Meteor Data Center is M2023-Y1.

In this work, we report the first conclusive observations of meteors produced
by dust ejected from comet 46P/Wirtanen. In Section 2, we describe the
hardware and methods used by the Global Meteor Network. In Section 3, we
present the results of observations and the comparison to predictions.

##  2 Methods

The Global Meteor Network (GMN111GMN website: https://globalmeteornetwork.org/
(accessed Jan 8, 2024)) is a professional-amateur consortium that currently
operates over 1000 video meteor cameras globally (Vida et al., 2021). The
network has over 200 cameras in the Southwest Pacific region, mostly operated
by Fireballs Aotearoa222Fireballs Aotearoa: https://fireballs.nz/ (accessed
Dec 25, 2023) in New Zealand, Perth Observatory in Western Australia333Perth
Observatory: https://www.perthobservatory.com.au/ (accessed Dec 25, 2023), and
a number of independent citizen scientists. An average GMN camera system
consists of a commercial off-the-shelf (COTS) video camera with a Sony IMX291
sensor, coupled to a 3.6 mm f/0.95 lens and a Raspberry Pi single-board
computer for data capture and processing. The optical setup achieves similar
performance to human vision, with a field of view (FoV) of $88^{\circ}\times
48^{\circ}$, a frame rate of 25 frames per second and a stellar limiting
magnitude in average sky conditions of $+6.0$ (Vida et al., 2021). In
addition, a pair of six-camera stations in Western Australia (Pemberton and
Toodyay) were operated with 6 mm lenses with a FOV of $53^{\circ}\times
30^{\circ}$ and a stellar limiting magnitude of $+6.5$.

Individual cameras report to a central server that performs meteor trajectory
correlation and meteor shower flux computation. Multi-station trajectories and
orbits are computed using the method described in Vida et al. (2020b), which
provides realistic uncertainties of orbital parameters by using Monte Carlo
error estimation. Meteor shower flux is computed from single-station
observations using the method described in Vida et al. (2022). The total
observed atmospheric area at the height of the meteor shower is estimated by
applying bias corrections, which take into account the theoretical radiant
elevation, meteor angular velocity, and measured camera sensitivity and
vignetting. An algorithm is employed to determine periods of clear skies by
matching observed stars to their computed positions and numbers assuming
modeled observational biases. The method produces a meteor activity profile in
units of meteoroids per 1000 square kilometres at a given mass limit, together
with a profile of observation efficiency, which informs the completeness of
the results (e.g., a peak might be missing in the activity profile if all
cameras were clouded out at that time). In practice, for any new meteor
shower, meteor trajectories are computed first and the radiant location,
radiant drift, radiant dispersion, meteor velocity, average meteor height, and
meteoroid mass distribution index are manually measured. These data are then
put in the flux algorithm.

##  3 Observation results and comparison to simulations

During the time of the predicted $\lambda$-Sculptorid activity, most of New
Zealand was under cloud cover, with only a handful of cameras of Fireballs
Aotearoa having clear skies the whole night. The weather in Australia was
excellent, with most cameras observing uninterrupted the whole night.
Qualitatively speaking, the observed activity was very low, with each camera
observing on the order of one $\lambda$-Sculptorid meteor during the whole
night.

###  3.1 Trajectories and orbits

A total of 23 $\lambda$-Sculptorid meteoroid trajectories and orbits were
computed, the details of which are given in Table LABEL:tab:trajectories. All
were observed in either New Zealand or Australia, except for one each from
South Korea and Bulgaria where the radiant was under the horizon but the
trajectories were bent by Earth’s gravity enabled by the extremely low speed
of the shower (i.e., zenithal attraction). The observed median geocentric
radiant is $\alpha_{g}=6.89^{\circ}$, $\delta_{g}=-38.89^{\circ}$ in
equatorial and $\lambda_{g}-\lambda_{\odot}=88.10^{\circ}$,
$\beta_{g}=-38.19^{\circ}$ in Sun-centered ecliptic coordinates. The radiant
dispersion, measured as the median angular separation from the median radiant
(Moorhead et al., 2021), is $0.96^{\circ}$. The median radiant measurement
error is $0.52^{\circ}$, meaning that the true physical radiant dispersion has
been resolved. The median observed geocentric velocity is $10.00\pm 0.25$ km
s-1.

Figure 1: Comparison between the geocentric radiants measured by GMN (crosses)
and CMOR (circled crosses) and the various theoretical radiants proposed by
Vaubaillon et al. (2023). The models are marked by the initials of individual
co-authors. The coloured circles are radiants predicted by AE, based on the
Egal et al. (2019) model, with mm-sized particles having a dark edge (to the
left of the smaller particles). Triangles are model radiants predicted by JV
using the Vaubaillon et al. (2005a) model. The radiants observed by the GMN
are shown as crosses. The error bars are not plotted for better readability,
but the average radiant measurement error is $\sim 0.5^{\circ}$.

Figure 1 shows the comparison between model radiants and the observed GMN and
CMOR radiants. The observed GMN radiant locations generally match well with
the models. The mean observed geocentric declination matches almost exactly,
with some models predicting it to be at the observed $-38.8^{\circ}$, while
the rest are all between $-38.0^{\circ}$ and $-40.4^{\circ}$ for the 1974
trail. However, there is a $\sim 1^{\circ}$ shift in right ascension from the
mean model radiant locations. In terms of the spread, the AE model radiants
extend about $8^{\circ}$ along the declination, while the JV radiants extend
$\sim 2^{\circ}$ along the right ascension, matching the GMN video
observations best. All models predicted a mean encounter geocentric velocity
in the range between 9.8 and 10.3 km s-1, which perfectly matches the observed
value of $10.00\pm 0.25$ km s-1.

In addition to GMN, CMOR observed a total of four $\lambda$-Sculptorid
meteors, despite being located in Canada. Two had large measurement
uncertainties due to the extremely low speed. The other two have been observed
well and presented in the figure. The improved atmospheric deceleration
correction for CMOR (Froncisz et al., 2020) enabled accurate measurement of
the pre-atmospheric speed of these slow meteors. The electron line densities
for the two meteors are around $10^{14}$ e m-1, translating to a peak meteor
magnitude of about +5.5 and 3–5 mm diameter particles (Weryk & Brown, 2013).
To confirm the validity of the detection, a period of 20 days before the
shower was investigated for additional detections, and not a single radiant
was observed by CMOR within a $20^{\circ}$ radius from the shower during that
time. The two radiants (Fig. 1) were located exactly on the elongated radiant
spread modeled by AE, matching that model best.

For reference, the mean orbital parameters using GMN data have been computed
using the method of Jopek et al. (2006) and are given in Table 1 where they
are compared to the mean of simulated orbits (JV), and the orbit of the comet
46P/Wirtanen at epochs in 2018 (latest orbit) and the time of meteoroid
ejection in 1974. Compared to the comet, both the observed and simulated
meteoroids have a smaller orbit, with the perihelion just inside the Earth’s
orbit. The mean observed and simulated orbits compare well and are well within
the scatter in the orbital parameters for both (see Table
LABEL:tab:trajectories).

Table 1: Mean orbital elements of the observed $\lambda$-Sculptorids compared to the mean orbital elements of the simulated particles encountering the Earth in 2023 (JV model) and the comet 46P/Wirtanen555JPL Horizons: https://ssd.jpl.nasa.gov/tools/sbdb_lookup.html#/?sstr=46P (accessed Dec 25, 2023). Parameter |  $\lambda$-Sculptorids | Simulated | 46P/Wirtanen | 46P/Wirtanen |
---|---|---|---|---|---
Epoch | J2000 | J2000 | 2458465.5 | 2442240.5 |
Date | 2023-12-12 | 2023-12-12 | 2018-12-13 | 1974-07-12 |
a | 2.891 | 3.029 | 3.092662 | 3.255261 | AU
q | 0.984566 | 0.980229 | 1.05535538 | 1.255701 | AU
e | 0.65946 | 0.676399 | 0.6587550 | 0.614255 |
i | 9.200 | 8.364 | 11.747548 | 12.2672 | deg
$\Omega$ | 79.925 | 79.432 | 82.157634 | 84.2087 | deg
$\omega$ | 359.915 | 0.284 | 356.341072 | 351.8580 | deg

###  3.2 Physical properties

The shower meteors exhibited median begin and end heights of $90.1\pm 1.2$ km
and $78.2\pm 2.9$ km, respectively. The median meteor peak height is $84.2\pm
2.5$ km, translating into an F parameter of $0.54\pm 0.13$. The observed
absolute peak magnitudes ranged from the faintest meteor at $+2.40$ to the
brightest at $-0.45$. The photometric masses were computed on integrated light
curves using a fixed luminous efficiency of $\tau=0.7\%$ (Vida et al., 2018).
The observed meteoroids had masses between 0.15 – 4.12 g, with a median mass
of 0.47 g. Using a bulk density of 500 kg m-3 (Ceplecha et al., 1998), these
masses correspond to diameters between 8 - 25 mm, and the median value of 12
mm.

We computed the Ceplecha (1958) $K_{B}$ parameter to characterize the physical
composition. Cordonnier et al. (2024) calibrated the parameter on GMN data and
found that a value of $-0.1$ needs to be subtracted from the original
definition, a correction that we also applied. The shower had a mean $K_{B}$
of $6.972\pm 0.096$, putting the meteors into group C1, defined as regular
cometary material from short-period comets (Ceplecha, 1988). This result is
consistent with the comet’s origin and orbit, making the meteoroids similar to
the Taurids, for instance. A similar value of $K_{B}$ has also been observed
for the 2022 outburst of the $\tau$-Herculids (Egal et al., 2023). That
outburst was caused by similarly-aged meteoroids, ejected in 1995. Both comets
were on a similar orbit with a $q\approx 1$ and the measured $K_{B}$ for the
$\tau$-Herculids is $6.9\pm 0.2$ (Koten et al., 2023). This is in contrast to
the Draconids, which are also young (Egal et al., 2019), and have a parent
body on a similar orbit, but are much more fragile, classified as group D
(Koten et al., 2007). This indicates the physical structural strength of
meteoroids is not only a function of age, but is inherent to the specificity
of the material present in the parent comet.

###  3.3 Activity profile

Due to the small number of observed meteors, the population index has been
difficult to measure. Using the method of Vida et al. (2020a), we found a mass
index of $s=2.25^{+1.5}_{-0.52}$ and a population index of
$r=3.23^{+3.03}_{-0.85}$. The errors are large due to the small sample size,
making choosing a single nominal value difficult. We erred on the side of
caution, choosing values of $s=2.2$ and $r=3.0$ which have been traditionally
considered in the literature as values appropriate for showers rich in small
particles (Rendtel, 2004), as indicated from observations of 46P (Kareta et
al., 2023; Vaubaillon et al., 2023). The chosen value is well within the
uncertainty.

Figure 4 in the appendix shows the observed flux profile of the
$\lambda$-Sculptorids and the data is given in Table LABEL:tab:flux. The
shower peaked at solar longitude $\lambda_{\odot}=259.988^{\circ}\pm
0.042^{\circ}$ (2023-12-12 15:04 UTC $\pm$ 1 h). The peak flux was
$0.179^{+0.073}_{-0.057}$ meteoroids per 1000 km2 per hour at a limiting
magnitude of $+5.42$ and limiting mass of $1.5\times 10^{-5}$ kg. Translated
to zenithal hourly rate (ZHR), the peak activity was $0.65^{+0.24}_{-0.20}$
meteors per hour. The observed activity period spanned solar longitudes
between $259.735^{\circ}$ and $260.318708^{\circ}$ (09:06 UTC to 22:53 UTC),
with the threshold ZHR of around 0.1 meteors per hour. The network had
excellent observational coverage throughout the activity period and had no
coverage gaps. The minimum time-area product (TAP) per bin is set to 15,000
km2 h and the minimum number of meteors per bin is set to 10, allowing for a
temporal resolution of about 1 hour. The bin duration was limited by the
number of meteors in each bin and not the TAP, showing the scarcity of
observed meteors.

Figure 2: Comparison between the observed flux profile of the
$\lambda$-Sculptorids with the predictions of Vaubaillon et al. (2023).
Coloured lines indicate the maximum activity time predicted by the different
models presented in Table 2 of Vaubaillon et al. (2023), and marked by the
initials of the co-authors. The solid lines illustrate the modeled activity
predicted by AE for particles with sizes above (blue) or below (red) one
millimetre, with nodal-crossing locations closer than 0.02 AU from the Earth’s
orbit at the time of the shower (AE1 model). The black symbols represent the
flux measured by GMN at a limiting magnitude of +6.5.

Figure 2 shows the comparison between the predicted and observed activity
profiles. Vaubaillon et al. (2023) found that different ejection conditions at
the comet highly influence the shower’s predicted time, which varied from
259.71∘ to 260.20∘ in solar longitude. In addition, the trails released by 46P
display a complicated dynamical evolution that is typical of JFC meteoroid
stream (Vaubaillon et al., 2004). This is particularly true for the 1974
trail, which suffered a close encounter with Jupiter in 1984 that
significantly changed the meteoroids’ orbital elements, causing the positions
of the comet and the trail to reverse, putting the meteoroids in a leading
position in front of the comet (see the comparison of the orbital elements
before and after the encounter in Figure 5 ).

All models in Vaubaillon et al. (2023) predicted a meteor activity caused by
the 1974 trail. However, only the smallest meteoroids ($<$1 mm) of the trail
were found to approach the Earth in 2023, with masses below the detection
limit of GMN cameras. This discrepancy can be resolved if models considered
lower particle densities than the predicted values of 500 to 1000 kg m-3.
Additional simulations conducted by JV with a density of 100 kg m-3 show that
massive particles from the 1974 trail are able to reach the Earth in 2023,
with radiants and arrival times similar to those of Vaubaillon et al. (2023)
and matching the observed radiant locations but not the peak time and activity
profile. This low density is plausible as the shower’s $K_{B}$ parameter is
similar to that of the $\tau$-Herculids which also had a very low measured
bulk density of 250 kg m-3 (Egal et al., 2023).

Additional investigations of the AE1 simulations, motivated by the
observational constraints, highlight the influence of the particles’ selection
criterion on the modeled activity profile. In the simulations, only particles
crossing the ecliptic plane within a distance $\Delta X$ and time $\Delta T$
from the Earth are retained as potential impactors. For a standard $\Delta
X<0.02$ AU and $\Delta T\pm$ 7 days, only particles from the 1974 trail and
the 1900-1908+ trails produced detectable meteors (model AE1 in Vaubaillon et
al. (2023)), as shown in Figure 2.

By increasing $\Delta T$ to 20 days, we find the modeled profile to be in
better agreement with the observations (blue curve in Figure 3). The temporal
$\Delta T$ selection amounts to replacing each simulated particle $p$ with a
swarm of particles of identical orbits centred on $p$, which crosses the
ecliptic plane at the nodal during a period of 2$\Delta T$. Large $\Delta T$
values, representing a high uncertainty on the particles’ position along the
orbits, have been employed to successfully predict the return of past meteor
showers (Jenniskens & Vaubaillon, 2008; Egal et al., 2020).

With this less restrictive $\Delta T$ criterion, several trails ejected prior
to 1908 are found to contribute to the shower’s activity in 2023. The
resulting activity profile reproduces well the timing and duration reported
for the shower. In contrast, the modeled radiants remained similar to those
presented in Figure 1, and do not reproduce the observed spread in right
ascension as well as the JV model. While additional observations could help
assess the real contribution of trails ejected from the comet prior to 1974,
no significant activity of the $\lambda$-Sculptorid is expected until 2045 in
the AE1 model.

Figure 3: Updated modeled activity (postdiction) of the $\lambda$-Sculptorid
shower from the AE1 simulation data set, for sub-mm (green) and mm-sized
(cyan) particles. In Vaubaillon et al. (2023), only particles crossing the
ecliptic plane closer than $\Delta r=$0.02 AU and within $\Delta T\pm$ 7 days
from the Earth were retained in AE1’s simulation. By increasing the time
selection criterion to 20 days, more mm-sized particles ejected from 46P prior
to 1908 approached the Earth in 2023. The resulting activity profile (dark
blue) is a better match to the observations when including the contribution of
older trails.

##  4 Conclusions

We have presented the first observations of meteors from a new meteor shower
$\lambda$-Sculptorids produced by the comet 46P/Wirtanen. The dynamical
simulations by Vaubaillon et al. (2023) predicted that meteoroids from the
1974 trail encounter the Earth on December 12, 2023. The authors used several
different methods and thus the exact predicted time of the peak varied between
08:23 UT and 20:06 UT.

A total of 23 multi-station meteors were observed by video meteor cameras of
the Global Meteor Network for which trajectories were correlated, and a total
of 172 from single-station $\lambda$-Sculptorids were used to estimate the
flux. The activity peaked at 2023-12-12 15:04 UTC $\pm$ 1 h (solar longitude
$\lambda_{\odot}=259.988^{\circ}\pm 0.042^{\circ}$), while the total activity
period (ZHR $>$ 0.1) spanned between 09:06 UTC to 22:53 UTC (solar longitudes
$259.735^{\circ}$ and $260.318708^{\circ}$). The shower peaked at a ZHR of
$0.65^{+0.24}_{-0.20}$ meteors per hour.

Due to the slow in-atmosphere speed of $\sim 15$ km s-1, only the largest
meteoroids were observed, with an average size of 10 mm. The measured value of
$K_{B}=7.0\pm 0.1$ indicates an ordinary short-period comet composition,
similarly to the recent $\tau$-Herculid outburst in 2022, which was produced
by similarly young meteoroids ejected in 1995.

Trajectory, orbit, and activity level observations by the Global Meteor
Network all matched the meteoroid stream dynamical simulations well overall.
The radiants best match the predictions of JV for the 1974 trail if a very low
bulk density of 100 kg m-3 is assumed. For higher densities, mm-sized and
larger meteoroids do not reach the Earth in 2023 in all dynamical simulations.
Alternatively, the observed activity profile and the mm-sizes can be achieved
using older trails and if a larger threshold of time and range from the orbit
is taken into account (i.e., AE model). However, this model reproduces the
radiant structure less accurately than other models. The fundamental
difficulty in reproducing the observations stems from the close encounter of
the 1974 trail with Jupiter in 1984, which caused a significant shift in the
orbital parameters. Any small model uncertainties are amplified by that event,
setting a practical limit on the reproducibility of the observations. This
makes the $\lambda$-Sculptorids an excellent data point for future model
validation and improvement, as small differences in the model assumptions make
large differences in the final result, helping to identify the best approach
and model parameters.

## Acknowledgements

The Global Meteor Network (GMN) data are released under the CC BY 4.0 license.
The authors thank all GMN camera operators and contributors who are listed in
Appendix C. We also thank Peter Brown for providing CMOR observations of the
new shower.

QY was supported by NASA grant 80NSSC21K0156, DV and AE were supported in part
by the NASA Meteoroid Environment Office under cooperative agreement
80NSSC21M0073.

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##  Appendix A Meteor trajectories and orbits

Table 2: Trajectory and orbit parameters of the observed meteors by the Global Meteor Network. Time (UTC) | $\lambda_{\odot}$ | $\alpha_{g}$ | $\delta_{g}$ | $V_{g}$ | $a$ | $e$ | $i$ | $q$ | $\Omega$ | $\omega$ | $\pi$ | $h_{B}$ | $h_{E}$ | $h_{\mathrm{peak}}$ | $M_{\mathrm{peak}}$ | $K_{B}$
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---
| (deg) | (deg) | (deg) | (km/s) | (au) |  | (deg) | (au) | (deg) | (deg) | (deg) | (km) | (km) | (km) | (mag) |
09:41:46.307 | 259.760586 | 7.84 | -38.62 | 10.392 | 3.140 | 0.6864 | 9.439 | 0.9846310 | 79.768747 | 0.30 | 80.07 | 90.218 | 76.819 | 84.199 | +0.21 | 6.94
|  | 0.32 | 0.18 | 0.074 | 0.070 | 0.0069 | 0.038 | 0.0000000 |  | 0.14 | 0.14 | 0.050 | 0.040 |  |  |
10:30:52.915 | 259.795268 | 7.16 | -38.43 | 9.900 | 2.832 | 0.6523 | 8.991 | 0.9846280 | 79.802844 | 0.08 | 79.88 | 89.853 | 78.091 | 81.758 | +0.46 | 6.97
|  | 0.21 | 0.20 | 0.061 | 0.032 | 0.0040 | 0.079 | 0.0000000 |  | 0.10 | 0.10 | 0.030 | 0.020 |  |  |
10:45:53.244 | 259.805864 | 7.76 | -39.13 | 10.579 | 3.254 | 0.6974 | 9.668 | 0.9846250 | 79.813104 | 0.07 | 79.88 | 89.906 | 81.326 | 86.231 | +1.65 | 7.00
|  | 1.77 | 1.10 | 0.684 | 0.901 | 0.0542 | 0.447 | 0.0002000 |  | 1.08 | 1.08 | 0.160 | 0.170 |  |  |
10:55:57.111 | 259.812971 | 5.82 | -40.22 | 10.359 | 3.060 | 0.6782 | 9.558 | 0.9845520 | 79.819086 | 358.87 | 78.69 | 89.323 | 77.529 | 81.388 | -0.07 | 7.03
|  | 0.63 | 0.77 | 0.085 | 0.046 | 0.0049 | 0.187 | 0.0000000 |  | 0.44 | 0.44 | 0.060 | 0.060 |  |  |
11:05:57.961 | 259.820043 | 8.29 | -39.09 | 10.100 | 2.896 | 0.6601 | 9.365 | 0.9846180 | 79.826519 | 0.34 | 80.17 | 88.731 | 77.457 | 81.778 | -0.45 | 7.07
|  | 0.59 | 0.44 | 0.140 | 0.131 | 0.0130 | 0.065 | 0.0000000 |  | 0.33 | 0.33 | 0.050 | 0.030 |  |  |
12:00:04.960 | 259.858260 | 6.56 | -38.65 | 9.861 | 2.808 | 0.6494 | 8.955 | 0.9846150 | 79.864074 | 359.71 | 79.58 | 91.385 | 77.007 | 87.773 | +1.77 | 6.86
|  | 0.42 | 0.14 | 0.134 | 0.067 | 0.0084 | 0.152 | 0.0000000 |  | 0.14 | 0.14 | 0.070 | 0.060 |  |  |
12:46:23.484 | 259.890963 | 6.58 | -39.45 | 9.782 | 2.722 | 0.6383 | 9.057 | 0.9846060 | 79.902111 | 359.45 | 79.35 | 92.840 | 77.232 | 83.906 | +0.20 | 6.75
|  | 0.19 | 0.33 | 0.095 | 0.070 | 0.0088 | 0.021 | 0.0000000 |  | 0.18 | 0.18 | 0.070 | 0.030 |  |  |
12:57:12.681 | 259.898605 | 6.79 | -39.27 | 9.831 | 2.755 | 0.6426 | 9.076 | 0.9846140 | 79.909016 | 359.59 | 79.50 | 90.072 | 72.864 | 81.493 | -0.44 | 6.94
|  | 0.33 | 0.17 | 0.057 | 0.043 | 0.0058 | 0.016 | 0.0000000 |  | 0.13 | 0.13 | 0.020 | 0.020 |  |  |
13:01:31.386 | 259.901649 | 6.27 | -37.72 | 9.848 | 2.853 | 0.6549 | 8.739 | 0.9846130 | 79.907307 | 359.85 | 79.76 | 89.511 | 81.264 | 85.819 | +0.95 | 7.03
|  | 0.56 | 0.99 | 0.158 | 0.052 | 0.0061 | 0.336 | 0.0000000 |  | 0.24 | 0.24 | 0.070 | 0.060 |  |  |
13:07:48.998 | 259.906093 | 6.26 | -37.86 | 9.996 | 2.942 | 0.6653 | 8.868 | 0.9846170 | 79.916954 | 359.78 | 79.70 | 89.483 | 77.391 | 83.160 | +1.26 | 7.00
|  | 0.27 | 1.65 | 0.440 | 0.344 | 0.0435 | 0.033 | 0.0000000 |  | 0.42 | 0.42 | 0.130 | 0.130 |  |  |
13:14:46.735 | 259.911011 | 6.89 | -39.91 | 9.730 | 2.666 | 0.6307 | 9.134 | 0.9846020 | 79.920482 | 359.43 | 79.35 | 88.251 | 79.740 | 83.293 | +1.11 | 7.06
|  | 0.24 | 0.41 | 0.097 | 0.033 | 0.0048 | 0.154 | 0.0000000 |  | 0.14 | 0.14 | 0.020 | 0.010 |  |  |
13:21:43.108 | 259.915911 | 7.09 | -39.44 | 9.903 | 2.783 | 0.6462 | 9.186 | 0.9846120 | 79.925115 | 359.66 | 79.58 | 92.288 | 74.862 | 81.079 | -0.43 | 6.78
|  | 0.19 | 0.18 | 0.024 | 0.003 | 0.0003 | 0.066 | 0.0000000 |  | 0.06 | 0.06 | 0.020 | 0.020 |  |  |
13:22:48.440 | 259.916680 | 6.04 | -38.38 | 9.692 | 2.732 | 0.6396 | 8.740 | 0.9846030 | 79.921885 | 359.55 | 79.47 | 91.239 | 80.946 | 85.689 | +0.92 | 6.89
|  | 0.25 | 0.15 | 0.015 | 0.012 | 0.0016 | 0.045 | 0.0000000 |  | 0.11 | 0.11 | 0.030 | 0.030 |  |  |
13:30:12.540 | 259.921907 | 10.80 | -38.57 | 10.269 | 2.972 | 0.6688 | 9.610 | 0.9844630 | 79.926941 | 1.57 | 81.49 | 89.407 | 82.104 | 84.754 | +2.40 | 7.06
|  | 2.30 | 0.28 | 0.182 | 0.060 | 0.0074 | 0.366 | 0.0001000 |  | 0.95 | 0.95 | 0.150 | 0.120 |  |  |
13:44:07.285 | 259.931732 | 9.26 | -37.94 | 10.364 | 3.122 | 0.6847 | 9.411 | 0.9845450 | 79.940239 | 1.07 | 81.01 | 90.921 | 78.231 | 84.105 | +0.49 | 6.90
|  | 0.65 | 1.74 | 0.466 | 0.186 | 0.0245 | 0.697 | 0.0001000 |  | 0.32 | 0.32 | 0.190 | 0.060 |  |  |
14:39:26.951 | 259.970805 | 6.97 | -39.04 | 10.235 | 3.020 | 0.6739 | 9.335 | 0.9846000 | 79.978607 | 359.68 | 79.66 | 90.153 | 79.277 | 86.483 | +0.80 | 6.97
|  | 0.20 | 0.15 | 0.034 | 0.011 | 0.0012 | 0.068 | 0.0000000 |  | 0.07 | 0.07 | 0.020 | 0.010 |  |  |
15:02:38.789 | 259.987187 | 6.28 | -39.95 | 9.931 | 2.789 | 0.6470 | 9.236 | 0.9846210 | 80.002258 | 359.10 | 79.10 | 90.100 | 71.945 | 76.310 | -0.26 | 7.17
|  | 0.12 | 0.09 | 0.026 | 0.018 | 0.0023 | 0.011 | 0.0000000 |  | 0.08 | 0.08 | 0.070 | 0.040 |  |  |
15:24:13.360 | 260.002425 | 6.26 | -37.78 | 10.088 | 3.009 | 0.6728 | 8.915 | 0.9845980 | 80.009246 | 359.75 | 79.76 | 88.584 | 80.556 | 85.417 | +0.99 | 7.09
|  | 0.72 | 0.75 | 0.072 | 0.016 | 0.0017 | 0.258 | 0.0000000 |  | 0.18 | 0.18 | 0.040 | 0.050 |  |  |
15:32:00.210 | 260.007921 | 9.66 | -38.34 | 9.938 | 2.804 | 0.6489 | 9.221 | 0.9845250 | 80.015119 | 1.11 | 81.12 | 88.757 | 78.596 | 83.334 | +0.88 | 7.07
|  | 1.06 | 0.29 | 0.026 | 0.010 | 0.0013 | 0.064 | 0.0000000 |  | 0.55 | 0.55 | 0.040 | 0.070 |  |  |
16:06:14.321 | 260.032097 | 7.38 | -39.37 | 10.243 | 2.996 | 0.6714 | 9.442 | 0.9846270 | 80.038368 | 359.73 | 79.77 | 91.896 | 83.424 | 88.004 | +1.24 | 6.96
|  | 0.40 | 0.30 | 0.121 | 0.077 | 0.0085 | 0.109 | 0.0000000 |  | 0.27 | 0.27 | 0.050 | 0.040 |  |  |
16:33:46.541 | 260.051545 | 6.75 | -39.84 | 10.218 | 2.965 | 0.6679 | 9.464 | 0.9845640 | 80.057597 | 359.29 | 79.35 | 90.695 | 76.727 | 85.900 | +0.13 | 6.94
|  | 0.67 | 0.08 | 0.047 | 0.041 | 0.0049 | 0.022 | 0.0000000 |  | 0.32 | 0.32 | 0.040 | 0.080 |  |  |
16:55:42.027 | 260.067029 | 8.74 | -38.89 | 10.120 | 2.909 | 0.6616 | 9.381 | 0.9845780 | 80.073024 | 0.47 | 80.55 | 90.502 | 81.624 | 84.233 | +1.90 | 6.95
|  | 1.00 | 0.20 | 0.031 | 0.011 | 0.0012 | 0.080 | 0.0000000 |  | 0.50 | 0.50 | 0.070 | 0.060 |  |  |
17:11:49.569 | 260.078417 | 6.08 | -38.88 | 9.610 | 2.663 | 0.6302 | 8.780 | 0.9845680 | 80.084380 | 359.33 | 79.42 | 90.613 | 82.306 | 85.386 | +1.35 | 6.92
|  | 0.72 | 0.28 | 0.066 | 0.033 | 0.0044 | 0.071 | 0.0000000 |  | 0.39 | 0.39 | 0.080 | 0.010 |  |  |
All meteors were observed on December 12. Standard deviations of individual
parameters are given in alternating rows. $\lambda_{\odot}$ is the solar
longitude, $\alpha_{g}$ and $\delta_{g}$ are geocentric right ascension and
declination in J2000, $V_{g}$ is the geocentric velocity, $a$ is the semi-
major axis, $e$ is the eccentricity, $i$ is the inclination, $q$ is the
perihelion distance, $\Omega$ is the ascending node, $\omega$ is the argument
of perihelion, $\pi$ is the longitude of perihelion, $h_{B}$ is the meteor
being height, $h_{E}$ is the end height, $h_{\mathrm{peak}}$ is the height of
peak magnitude, $M_{\mathrm{peak}}$ is the peak magnitude, and $K_{B}$ is the
Ceplecha (1958) parameter.
Table 2: continued. Table 3: Flux measurements by the GMN. $\lambda_{\odot}$ | Flux(+6.5) | Flux(+5.42) | ZHR | Meteor Count | TAP | Meteor LM | Radiant elev. | Radiant dist. | Ang vel.
---|---|---|---|---|---|---|---|---|---
(deg) | (met / 1000 km2 h) | (met / 1000 km2 h) | (met/h) |  | (1000 km2 h) | (mag) | (deg) | (deg) | (deg/s)
259.7351911 | $0.125_{-0.065}^{+0.106}$ | $0.038_{-0.020}^{+0.032}$ | $0.138_{-0.072}^{+0.115}$ | 10 | 79.760 | 5.36 | 52.58 | 61.34 | 6.08
259.8190395 | $0.138_{-0.072}^{+0.117}$ | $0.042_{-0.022}^{+0.035}$ | $0.152_{-0.079}^{+0.127}$ | 10 | 72.255 | 5.45 | 43.28 | 64.32 | 6.37
259.8635306 | $0.163_{-0.076}^{+0.116}$ | $0.050_{-0.024}^{+0.035}$ | $0.179_{-0.084}^{+0.127}$ | 13 | 79.795 | 5.46 | 53.29 | 60.99 | 6.03
259.9063104 | $0.360_{-0.108}^{+0.139}$ | $0.110_{-0.033}^{+0.042}$ | $0.395_{-0.118}^{+0.152}$ | 36 | 99.887 | 5.53 | 56.61 | 58.49 | 5.87
259.9473790 | $0.275_{-0.107}^{+0.149}$ | $0.084_{-0.033}^{+0.045}$ | $0.301_{-0.117}^{+0.164}$ | 20 | 72.807 | 5.46 | 52.77 | 61.90 | 5.95
259.9884477 | $0.588_{-0.186}^{+0.243}$ | $0.179_{-0.057}^{+0.074}$ | $0.646_{-0.204}^{+0.265}$ | 32 | 54.381 | 5.41 | 46.60 | 65.48 | 6.10
260.0312275 | $0.377_{-0.162}^{+0.235}$ | $0.115_{-0.049}^{+0.071}$ | $0.413_{-0.177}^{+0.258}$ | 16 | 42.488 | 5.41 | 43.32 | 66.76 | 6.10
260.0740073 | $0.435_{-0.197}^{+0.295}$ | $0.132_{-0.060}^{+0.090}$ | $0.477_{-0.216}^{+0.324}$ | 14 | 32.179 | 5.38 | 35.02 | 72.36 | 6.24
260.1321879 | $0.234_{-0.122}^{+0.197}$ | $0.071_{-0.037}^{+0.060}$ | $0.257_{-0.134}^{+0.216}$ | 10 | 42.696 | 5.33 | 26.98 | 78.32 | 6.23
260.3187080 | $0.113_{-0.056}^{+0.090}$ | $0.034_{-0.017}^{+0.028}$ | $0.124_{-0.062}^{+0.098}$ | 11 | 97.173 | 5.31 | 34.52 | 71.62 | 6.71
$\lambda_{\odot}$ is the time-area product (TAP) weighted solar longitude of
the bin. The two flux columns are fluxes at the standard magnitude of +6.5 and
the measured mean magnitude of +5.42. Meteor LM is the mean TAP-weighted
apparent meteor limiting magnitude, followed by the mean radiant parameters
weighted in the same way.
Table 3: continued.

##  Appendix B Additional figures

Figure 4: Flux profile of the $\lambda$-Sculpturids. The top inset shows the
flux at two different limiting magnitudes: black markers for the standard
$+6.5$ and gray markers for the observed mean of $+5.42$. The bottom inset
shows the observed time-area product (TAP) and the observed number of meteors,
together with the thresholds set on both. The dark gray shading inside
individual TAP bins shows the distribution of TAP inside each bin, revealing
any potential gaps in coverage. Figure 5: Orbits of simulated particles
encountering the Earth in 2023, ejected in 1974 (JV model). Particles are
coloured by the relative number density. The red marker is the orbit of
46P/Wirtanen. The close encounter with Jupiter in 1984 caused the so-called
reversal process, eventually making the meteoroids lead the parent.

##  Appendix C Extended acknowledgements

The authors thank all Global Meteor Network camera operators and contributors:

Adam Mullins, Aden Walker, Adrian Bigland, Adriana Roggemans, Alain Marin,
Alan Beech, Alan Maunder, Alan Pevec, Alan Pickwick, Alan Decamps, Alan Cowie,
Aled Powell, Alejandro Barriuso, Aleksandar Merlak, Alex Bell, Alex Haislip,
Alex Hodge, Alex Jeffery, Alex Kichev, Alex McConahay, Alex Pratt, Alex Roig,
Alex Aitov, Alexander Wiedekind-Klein, Alexandre Alves, Alfredo Dal’ Ava
Júnior, Amy Barron, Anatoly Ijon, Andre Rousseau, Andre Bruton, Andrea
Storani, Andrei Marukhno, Andres Fernandez, Andrew Campbell-Laing, Andrew
Challis, Andrew Cooper, Andrew Fiamingo, Andrew Heath, Andrew Moyle, Andrew
Washington, Andy Stott, Andy Sapir, Ange Fox, Angel Sierra, Angélica López
Olmos, Ansgar Schmidt, Anthony Hopkinson, Anthony Pitt, Anthony Kesterton,
Anton Macan, Anton Yanishevskiy, Anzhari Purnomo, Arie Blumenzweig, Arie
Verveer, Arnaud Leroy, Attila Nemes, Barry Findley, Bart Dessoy, Bela Szomi
Kralj, Bernard Côté, Bernard Hagen, Bev M. Ewen-Smith, Bill Cooke, Bill
Wallace, Bill Witte, Bill Carr, Bob Evans, Bob Greschke, Bob Hufnagel, Bob
Marshall, Bob Massey, Bob Zarnke, Bob Guzik, Brenda Goodwill, Brendan Cooney,
Brian Chapman, Brian Murphy, Brian Rowe, Brian Hochgurtel, Wyatt Hochgurtel,
Brian Mitchell, Bruno Bonicontro, Callum Potter, Carl Elkins, Carl Mustoe,
Carl Panter, Charles Thody, Charlie McCormack, Chris Baddiley, Chris Blake,
Chris Dakin, Chris George, Chris James, Chris Ramsay, Chris Reichelt, Chris
Chad, Chris O’Neill, Chris White, Christian Wanlin, Christine Ord, Christof
Zink, Christophe Demeautis, Christopher Coomber, Christopher Curtis,
Christopher Tofts, Christopher Brooks, Chuck Goldsmith, Chuck Pullen, Ciaran
Tangney, Claude Boivin, Claude Surprenant, Clive Sanders, Colin Graham, Colin
Marshall, Colin Nichols, Con Stoitsis, Creina Beaman, Daknam Al-Ahmadi, Damien
Lemay, Damien McNamara, Damir Matković, Damir Šegon, Damjan Nemarnik, Dan
Klinglesmith, Dan Pye, Daniel Duarte, Daniel J. Grinkevich, Daniela Cardozo
Mourão, Danijel Reponj, Danko Kočiš, Dario Zubović, Dave Jones, Dave Mowbray,
Dave Newbury, Dave Smith, David Akerman, David Attreed, David Bailey, David
Brash, David Castledine, David Hatton, David Leurquin, David Price, David
Rankin, David Robinson, David Rollinson, David Strawford, David Taylor, David
Rogers, David Banes, David Johnston, David Rees, Dean Moore, Denis Bergeron,
Denis St-Gelais, Dennis Behan, Derek Poulton, Didier Walliang, Dimitris
Georgoulas, Dino Čaljkušić, Dmitrii Rychkov, Dominique Guiot, Don Anderson,
Don Hladiuk, Dorian Božičević, Dougal Matthews, Douglas Sloane, Douglas Stone,
Dustin Rego, Dylan O’Donnell, Ed Breuer, Ed Harman, Edd Stone, Edgar Mendes
Merizio, Edison José Felipe Pérezgómez Álvarez, Edson Valencia Morales,
Eduardo Fernandez Del Peloso, Edward Cooper, Ehud Behar, Eleanor Mayers,
Enrico Pettarin, Enrique Arce, Enrique Chávez Garcilazo, Eric Lopez, Eric
Toops, Erwin van Ballegoij, Erwin Harkink, Eugene Potapov, Ewan Richardson,
Fabricio Borges, Fernando Dall’Igna, Fernando Jordan, Fernando Requena, Filip
Matković, Filip Mezak, Filip Parag, Fiona Cole, Florent Benoit, Francis
Rowsell, François Simard, Frank Lyter, Frantisek Bilek, Gabor Sule, Gaétan
Laflamme, Gareth Brown, Gareth Lloyd, Gareth Oakey, Garry Dymond, Gary Parker,
Gary Eason, Gavin Martin, Gene Mroz, Geoff Scott, Georges Attard, Georgi
Momchilov, Germano Soru, Gilton Cavallini, Gordon Hudson, Graeme Hanigan,
Graham Stevens, Graham Winstanley, Graham Henstridge, Greg Michael, Gustav
Frisholm, Gustavo Silveira B. Carvalho, Guy Létourneau, Guy Williamson, Guy
Lesser, Hamish Barker, Hamish McKinnon, Haris Jeffrey, Harri Kiiskinen,
Hartmut Leiting, Heather Petelo, Heriton Rocha, Hervé Lamy, Herve Roche,
Holger Pedersen, Horst Meyerdierks, Howard Edin, Hugo González, Iain Drea, Ian
Enting Graham, Ian Lauwerys, Ian Parker, Ian Pass, Ian A. Smith, Ian Williams,
Ian Hepworth, Ian Collins, Igor Duchaj, Igor Henrique, Igor Macuka, Igor
Pavletić, Ilya Jankowsky, Ioannis Kedros, Ivan Gašparić, Ivan Sardelić, Ivica
Ćiković, Ivica Skokić, Ivo Dijan, Ivo Silvestri, Jack Barrett, Jacques Masson,
Jacques Walliang, Jacqui Thompson, James Davenport, James Farrar, James Scott,
James Stanley, James Dawson, Jamie Allen, Jamie Cooper, Jamie McCulloch, Jamie
Olver, Jamie Shepherd, Jan Hykel, Jan Wisniewski, Janis Russell, Janusz
Powazki, Jason Burns, Jason Charles, Jason Gill, Jason van Hattum, Jason
Sanders, Javor Kac, Jay Shaffer, Jean Francois Larouche, Jean Vallieres, Jean
Brunet, Jean-Baptiste Kikwaya, Jean-Louis Naudin, Jean-Marie Jacquart, Jean-
Paul Dumoulin, Jean-Philippe Barrilliot, Jeff Holmes, Jeff Huddle, Jeff Wood,
Jeff Devries, Jeffrey Legg, Jeremy Taylor, Jesse Stayte, Jesse Lard, Jessica
Richards, Jim Blackhurst, Jim Cheetham, Jim Critchley, Jim Fordice, Jim
Gilbert, Jim Rowe, Jim Seargeant, Jochen Vollsted, Jocimar Justino, John W.
Briggs, John Drummond, John Hale, John Kmetz, John Maclean, John Savage, John
Thurmond, John Tuckett, John Waller, John Wildridge, John Bailey, Jon Bursey,
Jonathan Alexis Valdez Aguilar, Jonathan Eames, Jonathan Mackey, Jonathan
Whiting, Jonathan Wyatt, Jonathon Kambulow, Jorge Augusto Acosta Bermúdez,
Jorge Oliveira, Jose Carballada, Jose Galindo Lopez, José María García, José-
Luis Martín, Josip Belas, Josip Krpan, Jost Jahn, Juan Luis Muñoz, Jure
Zakrajšek, Jürgen Dörr, Jürgen Ketterer, Justin Zani, Karen Smith, Kath
Johnston, Kees Habraken, Keith Maslin, Keith Biggin, Ken Jamrogowicz, Ken
Lawson, Ken Gledhill, Kevin Gibbs-Wragge, Kevin Morgan, Klaas Jobse, Korado
Korlević, Kyle Francis, Lachlan Gilbert, Larry Groom, Laurent Brunetto, Laurie
Stanton, Lawrence Saville, Lee Hill, Len North, Leslie Kaye, Lev Pustil’Nik,
Lexie Wallace, Lisa Holstein, Llewellyn Cupido, Lorna McCalman, Louw Ferreira,
Lovro Pavletić, Lubomir Moravek, Luc Turbide, Lucia Dowling, Luciano Miguel
Diniz, Ludger Börgerding, Luis Fabiano Fetter, Maciej Reszelsk, Magda
Wisniewska, Manel Colldecarrera, Marc Corretgé Gilart, Marcel Berger, Marcelo
Domingues, Marcelo Zurita, Marcio Malacarne, Marco Verstraaten, Margareta
Gumilar, Marián Harnádek, Mariusz Adamczyk, Mark Fairfax, Mark Gatehouse, Mark
Haworth, Mark McIntyre, Mark Phillips, Mark Robbins, Mark Spink, Mark
Suhovecky, Mark Williams, Mark Ward, Marko Šegon, Marthinus Roos, Martin
Breukers, Martin Richmond-Hardy, Martin Robinson, Martin Walker, Martin
Woodward, Martin Connors, Martyn Andrews, Mason McCormack, Mat Allan, Matej
Mihelčić, Matt Cheselka, Matthew Howarth, Megan Gialluca, Mia Boothroyd,
Michael Cook, Michael Mazur, Michael O’Connell, Michael Krocil, Michał
Warchoł, Michel Saint-Laurent, Miguel Diaz Angel, Miguel Preciado, Mike
Breimann, Mike Hutchings, Mike Read, Mike Shaw, Mike Ball, Milan Kalina,
Minesh Patel, Mirjana Malarić, Muhammad Luqmanul Hakim Muharam, Murray Forbes,
Murray Singleton, Murray Thompson, Myron Valenta, Nawaz Mahomed, Ned Smith,
Nedeljko Mandić, Neil Graham, Neil Papworth, Neil Waters, Neil Petersen,
Nelson Moreira, Neville Vann, Nial Bruce, Nicholas Hill, Nicholas Ruffier,
Nick Howarth, Nick James, Nick Moskovitz, Nick Norman, Nick Primavesi, Nick
Quinn, Nick Russel, Nicola Masseroni, Nigel Bubb, Nigel Evans, Nigel Owen,
Nigel Harris, Nikola Gotovac, Nikolay Gusev, Nikos Sioulas, Noah Simmonds,
Ollie Eisman, Pablo Canedo, Paraksh Vankawala, Pat Devine, Patrick Franks,
Patrick Poitevin, Patrick Geoffroy, Patrik Kukić, Paul Cox, Paul Dickinson,
Paul Haworth, Paul Heelis, Paul Kavanagh, Paul Ludick, Paul Prouse, Paul Pugh,
Paul Roche, Paul Roggemans, Paul Stewart, Paul Huges, Pedro Augusto Hay Day,
Penko Yordanov, Pete Graham, Pete Lynch, Peter G. Brown, Peter Campbell-Burns,
Peter Davis, Peter Eschman, Peter Gural, Peter Hallett, Peter Jaquiery, Peter
Kent, Peter Lee, Peter McKellar, Peter Meadows, Peter Stewart, Peter Triffitt,
Peter Leigh, Pető Zsolt, Phil James, Philip Gladstone, Philip Norton, Philippe
Schaak, Phillip Wilhelm Maximilian Grammerstorf, Pierre Gamache, Pierre de
Ponthière, Pierre-Michael Micaletti, Pierre-Yves Pechart, Pieter Dijkema,
Predrag Vukovic, Przemek Nagański, Radim Stano, Rajko Sušanj, Raju Aryal,
Raoul van Eijndhoven, Raul Truta, Reinhard Kühn, Remi Lacasse, Renato Cássio
Poltronieri, René Tardif, Richard Abraham, Richard Bassom, Richard Croy,
Richard Davis, Richard Fleet, Richard Hayler, Richard Johnston, Richard
Kacerek, Richard Payne, Richard Stevenson, Richard Severn, Rick Fischer, Rick
Hewett, Rick James, Ricky Bassom, Rob Agar, Rob de Corday Long, Rob Saunders,
Rob Smeenk, Robert Longbottom, Robert McCoy, Robert Saint-Jean, Robert D.
Steele, Robert Veronneau, Robert Peledie, Robin Boivin, Robin Earl, Robin
Rowe, Roel Gloudemans, Roger Banks, Roger Morin, Roland Idaczyk, Rolf
Carstens, Romulo Jose, Ron James Jr, Roslina Hussain, Russell Jackson, Ryan
Frazer, Ryan Harper, Salvador Aguirre, Sam Green, Sam Hemmelgarn, Sarah
Tonorio, Scott Kaufmann, Sebastian Klier, Seppe Canonaco, Seraphin Feller,
Serge Bergeron, Sergio Mazzi, Sevo Nikolov, Simon Cooke-Willis, Simon
Holbeche, Simon Maidment, Simon McMillan, Simon Minnican, Simon Parsons, Simon
Saunders, Simon Fidler, Sofia Ulrich, Srivishal Sudharsan, Stacey Downton,
Stan Nelson, Stanislav Korotkiy, Stanislav Tkachenko, Stef Vancampenhout,
Stefan Frei, Stephane Zanoni, Stephen Grimes, Stephen Nattrass, Steve Berry,
Steve Bosley, Steve Carter, Steve Dearden, Steve Homer, Steve Kaufman, Steve
Lamb, Steve Rau, Steve Tonkin, Steve Trone, Steve Welch, Steven Shanks, Steven
Tilley, Stewart Doyle, Stuart Brett, Stuart Land, Stuart McAndrew, Sylvain
Cadieux, Tammo Jan Dijkema, Terry Pundiak, Terry Richardson, Terry Simmich,
Terry Young, Thiago Paes, Thomas Blog, Thomas Schmiereck, Thomas Stevenson,
Tihomir Jakopčić, Tim Burgess, Tim Claydon, Tim Cooper, Tim Gloudemans, Tim
Havens, Tim Polfliet, Tim Frye, Tioga Gulon, Tobias Westphal, Tom Warner,
Tommy McEwan, Tommy B. Nielsen, Torcuill Torrance, Tosh White, Tracey Snelus,
Trevor Clifton, Ubiratan Borges, Urs Wirthmueller, Uwe Glässner, Vasilii
Savtchenko, Ventsislav Bodakov, Victor Acciari, Viktor Toth, Vincent
McDermott, Vladimir Jovanović, Waily Harim, Warley Souza, Washington Oliveira,
Wenceslao Trujillo, William Perkin, William Schauff, William Stewart, William
Harvey, William Hernandez, Wullie Mitchell, Yakov Tchenak, Yfore Scott,
Yohsuke Akamatsu, Yong-Ik Byun, Yozhi Nasvadi, Yuri Stepanychev, Zach Steele,
Zané Smit, Zbigniew Krzeminski, Željko Andreić, Zhuoyang Chen, Zoran Dragić,
Zoran Knez, Zoran Novak, Asociación de Astronomía de Marina Alta, Costa Blanca
Astronomical Society, Perth Observatory Volunteer Group, Royal Astronomical
Society of Canada Calgary Centre.