Fireballs are quite rare with only a handful ever being observed. But in the South Australian desert, one of only two fireballs ever observed as falling into the Earth and Moon’s gravitational system was spotted. Dr Ellie Sansom from Curtin University told Gizmodo Australia about the unicorn event and why the region is one of the best places in the world to observe them.
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“The bright light seen when a rock from space flies through our atmosphere is called a meteor. Most people call them shooting stars,” Dr Sansom said. “When meteors are really bright, brighter than the planet Venus in the night sky, they become fireballs.”
Fireballs are already quite uncommon but Dr Sansom and a team of scientists spotted a phenomenon seen by very few people. In an October paper published in The Astronomical Journal, the group published a study identifying a minimoon fireball, sometimes called temporarily captured orbiters (TCOs).
“Across the three million kilometre-square of sky we observe, we get around one fireball a night,” Dr Sansom said.
“The fireball we published on recently was a bit special because it came close to Earth, was captured by its gravity and orbited us a few times before coming through our atmosphere.”
It’s particularly significant because the majority of fireballs spotted, Dr Sansom explained, come from a region of space between Mars and Jupiter called the main asteroid belt. Fireballs within a close proximity of Earth, TCOs, have only been observed once according to the study. Once.
Fireballs shooting across the sky close to Earth might sound like a frightening occurrence but Dr Sansom said there’s no cause for concern. The fireballs stop ‘burning’ when they get within 30 kilometre of our atmosphere.
You can thank the Desert Fireball Network (DFN) for spotting this rare event — a network of cameras across Australia (52 autonomous systems) that take pictures all night, every night and are tuned to seeing fireballs. The cameras are mostly set up in South and Western Australia due the perfect conditions present in the regions.
“There can be thousands of meteors a night, not all visible to the naked eye, but fireballs are more rare,” Dr Sansom said.
“We set up the DFN in Australia because of the large area we can cover, the clear skies, and the relative ‘ease’ of finding meteorites in desert environments. Meteorites with known orbits are incredibly valuable scientifically. Giving the spacial context to the valuable information they hold about solar system formation and evolution, [the meteorites are] akin to sample return missions. There are less than 40 out of the some 60,000 held in collections around the world.”
Most of us will never see a fireball in our lives, Dr Sansom admitted, but there are some other astronomical shows equally as exciting.
“If people do want a good show to watch, there is the Geminid meteor shower on December 14. Unfortunately, it will be a full moon, but anyone looking up for long enough should see some shooting stars,” Dr Sansom said.
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