Researchers think the fireball that exploded over the Australian desert on 22 August 2016 might have been a minimoon. The fireball was identified through images taken by a Desert Fireball Network— a network of cameras in Australia.
In case you aren’t aware, many meteorites, known as bolides enter Earth’s atmosphere and explode in mid-air. It is a very common phenomenon. But from the velocity analysis of the fireball codenamed, DN160822_03, researchers think the meteorite might have been in an orbit around Earth before falling down towards it. The rare phenomenon is known as a temporarily captured orbiter or a minimoon. Researchers explain, “Objects gravitationally captured by the Earth–Moon system are commonly called temporarily captured orbiters (TCOs), natural Earth satellites, or minimoons.”
The researchers explain in their study, TCOs are important as they are very close to us making it easier to study them and prepare for any type of asteroid mission. Prior to the DN160822_03, only one other TCO has been observed telescopically i.e. 2006 RH 120 which was in an orbit around Earth for about 11 months. Also, only one other bolide or fireball has been observed in such an orbit.
The researchers gathered data from six cameras spread over an area of hundreds of kilometres across the Australian desert to find the velocity and trajectory of the object. At a slow speed of 11 kilometres per second, the meteorite travelled through the atmosphere along a vertical trajectory. This velocity indicates that the fireball was potentially orbiting Earth before exploding in the atmosphere. The vertical trajectory eliminates the probability that the asteroid was slowed down by space debris.
The researchers explain: “In the future, events like these may be detected ahead of time using telescopes like the Large Synoptic Survey Telescope, and the pre-atmospheric trajectory can be verified.”