NASA believes that a mysterious, massive fireball that lit up southern Australia’s night sky last week could have been the size of a small car when it entered Earth’s atmosphere.
People in South Australia and western Victoria saw and heard the mystery object — now known to have been a meteorite — late on Tuesday May 21. It had a trail of light behind it as it descended.
Elyshia Norman wrote on The Advertiser’s Facebook page she saw the “huge fireball” coming over Mount Gambier, SA, about 11pm Tuesday.
“(It) made the whole house rumble, thought it was an earthquake,” she wrote.
VIDEO: This video was taken in the Adelaide suburb of Modbury
'Fireball' spotted by Adelaide resident
Many people in Victoria also witnessed the fireball, including Adelaide truck driver Darren Waters, who captured amazing video of it while driving on the Western Hwy, just east of Ararat, Victoria.
VIDEO: This video was taken in Melbourne
Fireball spotted in Melbourne
A NASA centre that studies asteroids and meteors captured information from sensors showing where the meteorite landed and how much energy it produced.
Information from the Center for Near-Earth Object Studies in California, US, shows the meteorite landing site as a reasonably large blue-green dot on the Center’s map of reported fireballs.
The meteorite reached 44,100kmh when it entered Earth’s stratosphere*. It then burned and broke up, with some parts landing about 300km west-south-west of Mount Gambier, SA in the Great Australian Bight.
Professor Phil Bland from Curtin University, WA, said “the energy deposited in our atmosphere when the thing exploded, 1.6 kilotonnes*”, was impressive.
“That’s very high,” he said.
“It’s in the range of a small nuclear weapon. Because it exploded at an altitude of 31.5km it didn’t do any damage.”
NASA aerospace engineer Dr Steve Chesley told ABC the object could have been the size of a small car or big couch when it entered the atmosphere, but high pressure caused it to break up and “small pieces the size of a fist or larger” could make their way to the surface as meteorites.
“You wouldn’t want it to land on your head,” he said. “But these wouldn’t really do any damage on the ground.
“What the folks there along the coast of South Australia saw was a spectacular light show, probably a very loud sonic boom that would rattle the windows, this wasn’t big enough to break windows I expect, and then just small pebbles falling to the Earth and not at hypersonic* velocities*, they slow down very quickly.”
The meteor reached “peak brightness” at an altitude* of 31.5km, travelling at 11.5km a second, with a calculated total impact energy of 1.6 kilotonnes over the water to our south.
In comparison, the nuclear bomb that exploded over Hiroshima, Japan, at the end of World War II had a total impact energy of 15 kilotonnes.
The meteorite over southern Australia came only two days after a meteor shower seen across the Northern Territory’s night sky.
Astronomers* know that such a busy night sky is perfectly normal and can happen a few times a year.
In fact, we’ve just experienced an annual meteor shower called Eta Aquarids.
Each year, from about mid-April to mid-to-late May, Earth moves through a cloud of debris left behind by Halley’s comet hundreds of years ago. The name Eta Aquarids comes from the constellation* called Aquarius, because it looks like the meteors come from the part of the sky we see Aquarius in.
Peak meteor viewing for Eta Aquarids is usually around the first week of May and you could see up to 50 meteors an hour if the sky is clear.
This was a good year for seeing Eta Aquarids in the Southern Hemisphere as the peak nights were at the same time as a new moon, so the sky was darker than when the moon is fuller.
Most meteors move past the Earth and don’t enter our atmosphere.
- Asteroid: large body made mainly of rock and metal, without an atmosphere, in orbit around the Sun
- Meteoroid: much smaller rock or particle in orbit around the Sun
- Meteor: shooting star. Occurs when a meteoroid enters Earth’s atmosphere and vaporises, which means turn from a solid or liquid into a gas
- Meteorite: any surviving bit of meteor that hasn’t vaporised and lands on Earth
- Comet: loose mass of ice, dust and rock, often in very long orbit around the Sun
- Sonic boom: a big noise from shockwaves a meteor makes when it explodes high up in Earth’s atmosphere; sounds similar to thunder
- stratosphere: middle layer of the Earth’s three layers of atmosphere
- kilotonnes: unit of explosive power equivalent to 1,000 tons of TNT; singular is kiloton
- hypersonic: faster than sound
- velocities: speeds
- altitude: height above sea level
- astronomers: scientists who study objects in space
- constellation: group of stars that are in a recognisable arrangement
- How fast was the meteor travelling when it entered the stratosphere?
- What altitude was the meteor when it was at its brightest?
- What and when is Eta Aquariids?
- What does an asteroid orbit?
- What is the difference between a meteor and a meteorite?
LISTEN TO THIS STORY
1. From Meteoroid to Meteorite
Carefully read the final part of the article, subtitled “Space Rocks”. Draw a picture and add some labels and captions to show the process from being a meteoroid to becoming a meteorite. Once your picture is complete, practice explaining the transformation out loud and when you are confident share your verbal explanation with a classmate.
Time: allow 25 minutes to complete this activity
Curriculum Links: English, Science
There are a lot of interesting words in this news article. Perhaps there are terms that are completely new to you, or ones you haven’t used before. Go through the article and highlight or write down any words that you think would be great additions to your vocabulary. Choose 3 of the words to write into a sentence. Then, throughout the next week, see if you can incorporate these words into conversations you have or other work that you do.
Time: allow 15 minutes to complete this activity
Curriculum Links: English, Science
The Sky is Falling
Imagine hearing a loud bang and then when you look up into the night sky, suddenly it’s raining stars! Some people would have thought it was amazing and beautiful, others might have panicked and thought the world was ending.
I want you to write a short story about the day the stars fell from the sky. You can use as much embellishment as you like, as most panicked retells are a little exaggerated to give the impact of emotions. Today, you get to play the role of the panicked citizens.
See if you can use some key facts from the article to match up the events. And use lots of description, emotions and short sentences to build suspense.
HAVE YOUR SAY: Have you ever seen a meteor, meteorite or comet?
No one-word answers. Use full sentences to explain your thinking. No comments will be published until approved by editors.