Bolide Impacts in Jupiter’s Atmosphere in 2020-2021

Since 2010 several amateur astronomers have discovered flashes of light that result from the collision of objects of 5-20 m in diameter, impacting in Jupiter’s atmosphere at velocities higher than 60 km/s. These objects release energies of the order of 10¹⁵-10¹⁶ J, or 200-1000 kiloton [1] and become observable even with small-size telescopes. Up to 2019, 6 such impact flashes have been observed by amateur astronomers [2-3]. In one case, the quality of the light-curve allowed to investigate the physical composition of the impacting object through the effect of its density when comparing with models of impacts and with the likely conclusion of a stony composition [4]. An important step forward has been the availability of software tools that allow to check video files of Jupiter to automatically search for the faint trace of an impact. The software DeTeCt is a free-software designed for the task [5] and available at: http://www.astrosurf.com/planetessaf/doc/project_detect.php

Here we report the characteristics of 3 additional impacts detected in 2020-2021. These were a very bright flash discovered on 13 September, which was simultaneously observed by at least 9 observers from Brazil to Germany. A new impact was discovered by Kothji Arimatsu from Kyoto University on 15 October 2021, running a dedicated telescope with two CMOS cameras, and also observed by amateur astronomers in Japan and Singapore. After finding this impact, one of these observers used the DeTeCt software on past observations acquired one year earlier on 11 Aug. 2020 finding an additional impact that had passed unnoticed. These 3 impacts in 2020 and 2021 were observed by a variety of cameras with different sensitivities to color. This allows a good quantification of the effective brightness temperature of the impact and a more accurate measurement of the energy released, and thus, a better estimation of the mass of the impactor. The event observed on 13 September 2021 was the brightest flash observed in Jupiter. The 15 October 2021 event was also brighter than most previous flashes and it impacted Jupiter in an area observed by the Junocam instrument 28 hours later. However, Junocam did not observe a remnant even at a spatial resolution over the impact area of ~30 km/pix. We present light-curves of these three impacts and their brightness temperatures from multi-wavelength observations. Brightness temperatures compare well with the spectra of a smaller impact observed in 2018 by the Juno mission [8]. From the light-curves and brightness temperatures we deduce masses, sizes and how these 3 new objects,  and the combined data of the DeTeCt project set ups new constrains in the current impact rate in the Jupiter System [3, 7]. We also evaluate the quality of the structures observed in the simultaneous lightcurves and their capability to constrain models of bolides impacting Jupiter’s atmosphere [2,4].

 

Figure: Composite images of the three impacts discussed in this work together with multi-wavelength lightcurves of the central impact from one of the colour videos obtained. The rate between blue and red is indicative of a high brightness temperature.

Acknowledgments

We are very grateful to all the observers of these impacts supplying the observations and reports used in this analysis. These are: (1) Victor PS Ang (Singapore), who observed the 2020-08-11 impact and was one of the 3 amateur observers of the 2021-11-15 impact. (2) Jose Luis Pereira (Brazil), Harald Paleske (Germany), Jean-Paul Arnould (France), Didier Walliang (France), Michel Jacquesson (France), Cosmin Sabdu Val (Romania), Jean-Christophe Griveau (France), who all observed and recorded videos of the 2020-09-13 impact together with additional colleagues operating their telescopes. In addition Maciej Libert (Germany), Simone Galelli (Italy) both reported visual observations of the impact looking at the eyepiece of their telescopes. (3) “Yotsu” (Japan) and Yasunobu Higa (Japan) who were two of the observers of the 2021-11-15 impact. We are also grateful to Kothji Arimatsu and the PONCOTS team from Kyoto Observatory for comments on the October 2021 impact they originally discovered and announced making possible its detection in amateur videos acquired from Singapore and Japan. In addition, we are extremely grateful to the many amateur astronomers taking part in the DeTeCt project and committing a large amount of their time to look for impacts.

References

[1] Hueso, R., Wesley A. et al. (2010). First Earth-based detection of a superbolide on Jupiter, The Astrophysical Journal Letters (721), 2010.

[2] Hueso, R. et al. (2013). Impact flux on Jupiter: From superbolides to large-scale collisions. Astronomy & Astrophysics, 560, A55.

[3] Hueso, R., Delcroix, M. et al. (2018). Small impacts on the giant planet Jupiter, Astronomy & Astrophysics, A68.

[4] Sankar, R. et al. (2020). Fragmentation modelling of the August 2019 impact on Jupiter, Montly Notices of the Royal Astronomical Society, 493, 4622-4630.

[5] Hueso, R. Et al. (2018). Detectability of possible space weather effects on Mars upper atmosphere and meteor impacts in Jupiter and Saturn with small telescopes. Journal of Space Weather and Space Climate, 8, A57.

[6] Delcroix, M. et al. (2019). Jupiter impact detection project, Europlanet Science Conference, EPSC2019-970.

[7] Delcroix, M. et al. (2020). Impact detection on Jupiter through amateur’s processing of their own videos using DeTeCt, Europlanet Science Conference, EPSC2020-775.

[8] Giles, R. S. et al. (2021). Detection of a Bolide in Jupiter’s atmosphere with Juno UVS, Geophysical Research Letters, 48, e2020GL091797.