A green fireball brighter than the full moon surprised Australians in Queensland and New South Wales with a massive bang Monday night, leaving questions about what occurred.
Adding to the confusion was the Lyridid meteor shower peaking this week, yet the strange object’s trajectory was incorrect for association with the annual meteor event. As the object detonated over Australia, the ensuing explosion likely reduced the object to such tiny shards that collection is highly improbable, prolonging the mystery and leaving residents guessing.
Lyrid Meteor Shower
The meteor shower occurring that night is named for the constellation Lyra, from where the meteors appear to pour. Southern hemisphere residents in Australia would have noticed the stream near the star Vega, although their window to do so would have been narrower than in the Northern Hemisphere.
The Lyrids are a stream of meteors ejected from the comet Thatcher, visible from Earth every April. New York City’s Alfred E. Thatcher was the first to discover the original comet back in 1861, with the comet not expected to return until 2278. Unlike their cometary parent, the meteor shower occurs annually, first noted all the way back in 687 BCE, with particularly spectacular outbursts occurring every 60 years. However, the Australian event was not one of those outburst events, as astronomers don’t expect the next one until 2042.
A Green Fireball Explosion
Shortly before 7:30 pm, roughly 20 miles in the sky over Australia, a suspected space rock exploded in a brilliant flash of green, although some reports mention blue. Traveling perhaps up to 25 miles a second, witnesses first caught sight of the object when it was about 60 miles up. Videos and claims of shaken homes flooded social media in the aftermath. Although early media reports suggested some connection to the Lyrid meteor shower, astronomers from Curtin University and the University of Southern Queensland quickly weighed in otherwise.
A major strike against the Lyrid theory was that it was much too early in the evening for the shower to be visible, as the meteors would not come into view until at least 9 pm. With the meteor stream moving in one direction, they appear to originate from a single point in the sky from the perspective of someone standing on Earth, called a “radiant.”
At the time of the explosion, that radiant would still have been below the horizon and, therefore, out of sight for Queensland and New South Wales viewers. Additionally, Lyrid meteors appear to originate from a radiant in the south, heading north in the southern hemisphere, yet the green fireball arrived from the north instead.
What was in the Night Sky?
With pieces of the object likely so minuscule as to escape notice by anyone who came across them, concrete physical evidence is unlikely to produce a positive identification. Still, astronomers have some theories. In addition to ruling out Lyrid, astronomers suggest that the object is unlikely to be anything man-made due to its tremendous speed, which may suggest a slingshot orbit around the sun.
Most likely, the object was a random space rock, such as an asteroid or comet, that appeared on the same night as the meteor shower in a complete coincidence.
If you witnessed the Monday night event, contact the International Meteor Organization with your story. Scientists seek any available data to more conclusively determine the object’s identity.
Ryan Whalen covers science and technology for The Debrief. He holds an MA in History and a Master of Library and Information Science with a certificate in Data Science. He can be contacted at ryan@thedebrief.org, and follow him on Twitter @mdntwvlf.