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Sonntag, 11. September 2022 - 07:02

Astronomie - Fire in the sky: on the trail of space rocks with New Zealand’s meteorite hunters

11.09.2022

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Weeks after installing a network of meteor-detecting cameras, the members of Fireballs Aotearoa were granted their dearest wish: a rock that fell to Earth

It looks like a scene from a crime show as a search party in hi-vis jackets walks in formation, heads down, searching the brush for clues. But this group is not looking for evidence of a crime, they are after something harder to find: celestial debris from the formation of our solar system.

On 28 August, just before 11pm, an immense bright light was seen streaking across New Zealand’s southern sky, followed by a sonic boom. The spectacle, like a brushstroke of white paint on black ink, was captured by 20 hi-tech cameras across Southland set up for this exact event – a meteor entering the atmosphere above, and hopefully landing in, New Zealand.

The next morning, eyewitness accounts and security camera footage started trickling in to a group called Fireballs Aotearoa, a recently established organisation made up of geologists, astronomers and citizen scientists.

The group was initially unsure what they were looking at – the flash was so bright and big that some of the cameras mistook it for the moon. Later that evening, after analysing the footage, the group discovered it was in fact a very sizeable meteor.

“It was at this point we realised ‘oh this is really big, this might have dropped something on the ground’,” says Thomas Stevenson, a second-year geology masters student at the University of Otago, and the Southland coordinator for Fireballs Aotearoa.

By triangulating footage from the network of meteor cameras, which contain highly sensitive sensors that pick up aberrations in light, the scientists could predict that a meteorite between 1kg and 30kg had likely fallen within a small area 20km west of Dunedin.

“It’s barely been two months since we started setting up meteor cameras in Otago and to have one land essentially in our back yard – we never expected this,” Stevenson says.

A few days after the fireball tore through the sky, a group of 22 excited geologists from the University of Otago faculty set out to find the rare and precious space rock, which could aid research into the formation of the solar system.

After a full day’s search, the team returned empty handed. But hope was not lost. Further trips are planned, which will take into account new meteorological analysis showing the wind could have pushed it a kilometre outside the original target site.

‘My heart beat a little faster’

Just nine confirmed meteorites have been discovered in New Zealand in the past 150 years, but many more will have fallen and never been found. Retrieving one can be difficult: New Zealand has a small population that is unlikely to spot most meteors entering the atmosphere, has rugged and dense terrain that can hinder the hunt for debris, and there is a lack of infrastructure to help triangulate the location of a landing.

But James Scott, an associate professor in the University of Otago’s geology department and a member of Fireballs Aotearoa, hopes that by enlisting the community, and installing special meteor sensors around the country, those dismal chances of finding a meteorite will improve.

“Many people will see a fireball say once or twice in their life, but what we have now is the ability to take that a little further … people are actually interested in collating information and I think that’s what we’re seeing now: an underlying interest in the night sky.”

It was a natural progression, as a geologist, to become interested in extraterrestrial rocks, Scott says, but it was a tiny splinter of a meteorite from Mars in a little New Zealand gem store that sparked his obsession.

“The first time I held a Martian meteorite, I’m pretty sure my heart beat a little faster,” Scott says. “You’re holding a rock that is older than anything we can pick up on Earth today … Most meteorites are pretty close in age to the formation of the solar system, just over 4.5 billion years old.”

Fireballs Aotearoa is based on a successful meteorite hunting group, the UK Fireball Alliance. It was set up in February to bring together scientists and citizens who share a fascination with meteorites, with the aim of recovering freshly fallen meteorites and encouraging the community to get involved.

Through the Curious Minds participatory science program – a government-run project to boost community engagement in science – Fireballs Aotearoa secured $20,000 to set up 20 cameras at schools and institutes across Southland. Eventually, the group wants to have cameras across the entire country.

He enjoys the fact the sensor cameras are relatively inexpensive and easy to set up and can record astronomy every night, especially “if you don’t feel like going and sitting out in the cold”. The cameras feed images to a small computer called a Raspberry Pi, which connects wirelessly to the internet and broadcasts information back to a central computer at the University of Otago, and to the Global Meteor Network.

The sudden community-wide boom in interest over fireballs has been sparked by two major events in the past two months – the Dunedin fireball and a daytime explosion over Wellington in July. Nearly 30 people have contacted Fireballs Aotearoa since then expressing interest in installing their own cameras, Taylor says.

For the celestially curious, fireball watching and meteorite hunting is an accessible way to directly contribute to science.

“You can contribute in a meaningful way, it can be a fun activity to be involved in and you can meet some really interesting people,” Taylor says. “It is a lifelong learning experience.”

Quelle: The Guardian

Astronomie - Fire in the sky: on the trail of space rocks with New Zealand’s meteorite hunters

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