Bolide Event in Penang During the Morning of 21 July 2021
During the early hours of the morning of Wednesday, 21 July 2021, people on Penang Island saw bright flashes of light in the dark sky followed by hearing a very loud bang coming from the sky. Lim Choon Kiat who is a member of the Astronomical Society of Penang was taking pictures of the night sky. He went out at 4.50 a.m. to make some calibrations on this telescope and camera equipment and went back inside his house again at 4.57 a.m. He heard the loud boom at 5.02 a.m. He said that it sounded like a sonic boom which is different from thunder or blasts on land. Lim posted his experience on the WhatsApp group of the Astronomical Society of Penang. By 6.00 a.m. there were many reports by people on Penang Island who also heard the loud boom and the flashes of light on the CCTV cameras that were installed in the front porches of their houses and these cameras also recorded the subsequent loud boom. An observer in Kulim also reported seeing the bright flashes.
Astronomical Society of Penang member Loh Chee Kean was able to record a video of the bright object moving over his observatory. His observatory camera was pointing north, facing the western sky. From the video, Loh was able to determine that the bright object was moving from the southwest of Penang Island towards the northeast. From the exact timings of the bright flashes of light and loud bang that were detected by house CCTV cameras located in Sungai Ara, Jelutong and Tanjung Bungah, Dr. Chong Hon Yew who is the President of the Astronomical Society of Penang was able to locate the exact location of the source of the loud explosion in the sky. The source of the explosion was high up in the atmosphere at a distance of 49 km to the north of Tanjung Bungah.
Dr. Chong said that the flashes of light and the loud explosion were caused by a bright bolide which originated from outer space that entered into the atmosphere near Penang at a very high speed. The intense heat and forces caused by the friction of the atmosphere with the bolide created the bright flashes and made the bolide to finally explode high in the atmosphere. Also from the loudness of the explosion which was heard in the various locations on Penang Island, Dr. Chong was able to determine that the sound energy of the explosion was 1.4 trillion joules of energy, or 1.4 terajoules or 1.4 TJ or 337 tonnes of TNT equivalent. This put the sound energy of the Penang bolide explosion to be about 2% of the energy of the Hiroshima bomb.
The CCTV cameras captured three bright flashes but only one loud explosion was heard. Actually 3 explosions occurred next to the bolide high in the atmosphere producing 3 booms. Because the wavelengths of sound energy are much longer that the wavelength of light and because of the diffraction of sound , by the time the 3 booms reached the Earth’s surface on Penang Island, the 3 booms have merged into one louder boom. Therefore, on the ground we could see 3 explosions with light but heard only one loud explosion with sound.
Reported by Dr Chong H.Y.
Photo credit to Mr. Kenny Loh C.K.