During lunar eclipse of January 21 , 2019 a meteoroid impacted the Moon producing a visible light flash .
The impact was witnessed by casual observers offering an opportunity to study the phenomenon from multiple geographical locations .
We use images and videos collected by observers in 7 countries to estimate the location , impact parameters ( speed and incoming direction ) and energy of the meteoroid .
Using parallax , we achieve determining the impact location at lat . -29.43 ^ { +0.30 } _ { -0.21 } , lon . -67.89 ^ { +0.07 } _ { -0.09 } and geocentric distance as 356553 km .
After devising and applying a photo-metric procedure for measuring flash standard magnitudes in multiple RGB images having different exposure times , we found that the flash , had an average G-magnitude \langle G \rangle = 6.7 \pm 0.3 .
We use gravitational ray tracing ( GRT ) to estimate the orbital properties and likely radiant of the impactor .
We find that the meteoroid impacted the moon with a speed of 14 ^ { +7 } _ { -6 } km/s ( 70 % C.L . )
and at a shallow angle , \theta < 38.2 degrees .
Assuming a normal error for our estimated flash brightness , educated priors for the luminous efficiency and object density , and using the GRT-computed probability distributions of impact speed and incoming directions , we calculate posterior probability distributions for the kinetic energy ( median K _ { med } = 0.8 kton ) , body mass ( M _ { med } = 27 kg ) and diameter ( d _ { med } = 29 cm ) , and crater size ( D _ { med } = 9 m ) .
If our assumptions are correct , the crater left by the impact could be detectable by prospecting lunar probes .
These results arose from a timely collaboration between professional and amateur astronomers which highlight the potential importance of citizen science in astronomy .