Australian skies have been graced with an astonishingly bright meteor with videos capturing both the visual feast and onlookers' stunned reactions as it flew overhead in the early hours of June 15.
The eerie, decidedly green glow, and apparently slow progression of the fireball through the skies of north-western Australia led to speculation this was something more than an ordinary, albeit very bright, meteor. Some speculated space junk, or pointed out, with 2020's record, this could be the year aliens decide to invade. However, Dr Ellie Sansom of the Desert Fireball Network (DFN) told IFLScience most of this was wrong.
The object in question was almost certainly a meteor rather than space junk. “Artificial materials tend to be red when they burn up and more sparkly,” Sansom said. “This was quite different, very green and fairly steady.” There is also no need to resort to theories about alien invasions, as on-brand as that would be for 2020.
The apparent slowness could be an illusion, Sansom added, since we don't know its distance. Based on the brightness witnessed, as demonstrated in the video below, Sansom thinks the object was about the size of a washing machine.
Unfortunately for Sansom, the path was too far north to be picked up by her network, which covers much of south-western and central Australia with wide-angle cameras to track the paths of incoming meteorites and identify where they land.
“Meteorites are incredible samples of early Solar System material, from them we can figure out how our Solar System formed, why there is water and even life on Earth,” Sansom told IFLScience. “We have about 60,000 meteorites, but fewer than 40 of those we know where they come from in the Solar System.” That information can only be obtained by observing a meteorites' incoming path with several cameras and triangulating to calculate its previous orbit; inspiring the creation of the DFN.
Australia was chosen because its large unpopulated areas offer dark skies, and once landed black meteorites stand out against the red sands of its deserts, the same reason they are often found in the vast white expanse of Antarctica.
In 2015 the project was rewarded when its cameras were used to track the path of an incoming meteorite, which was then recovered in a Hollywood-worthy race against time. The DFN has since been expanded into suitable parts of North America and Africa, with a goal of eventually covering 2 percent of the planet.
In 2017, the DFN photographed something that looked remarkably like this week's event, visible for 90 seconds over a span of 1,200 kilometers (720 miles). “We'd never seen anything like it before,” Sansom said. The path was so well calculated the chance of finding a meteorite would have been high if it had hit the ground. Unfortunately, that object had such a shallow entry angle it never got below 50 kilometers from the surface, instead heading off into space again, on an orbit that would take it out near Jupiter. Meteors can hit the atmosphere with speeds anywhere up to 71 km/s (160,000 mph). Friction slows them down – it's also this that produces the fantastic light show – but if their angle is shallow enough, as long as they stay above escape velocity, (11 km/s), escape is possible.
The similarities between the 2017 event and the one this week further north prompted media speculation this too was an Earth-grazer, but Sansom told IFLScience, “Three things could have happened, either it could have burnt up completely, dropped a meteorite, or had enough speed to go back into space.” At this stage, no one knows which is right.