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Race to find space rock near Dunedin

Sep 02, 2022

The race is on to find a fireball which is believed to have landed somewhere near Dunedin.

A spectacular fireball was captured by night-sky cameras shooting across the Otago region on August 28.

Only nine meteorites have been found on New Zealand soil over the last 150 years, but there were improved odds for finding this one.

University of Otago geology department Associate Professor James Scott told Morning Report the fireball on 28 August came in from the west of New Zealand.

"It shot across the Southern Alps and it was caught as a bright flash on ... cameras... they all picked up this extremely bright fireball heading down toward Dunedin," Scott said.

"A loud sonic boom followed the fireball, indicating a large size of the initial meteoroid entering the atmosphere."

As it entered the atmosphere the bright light was caused by much of the projectile burning up, but it was estimated between 1 and 10kg could have landed. That's "a pretty large one", Scott said - "unusual to get this sort of size."

People looking for it should watch out for a black rock, and if it was found soon before more dust and dirt covers it, it could have a shiny surface, he said.

"Quite bright and black, and the black is because when the rock was shooting through the atmosphere the surface was melting, and when it crystallizes it forms a glass, and that's what the black surface is on the outside."

A camera at the Beverly-Begg Observatory in Dunedin caught the August 28 meteor. This is a single image of the fireball exploding, and the second line of light is caused by an internal reflection and is not a second meteor (Image supplied/University of Otago/James Scott).

It was likely more space rock had reached New Zealand than the nine previously confirmed - they had just not been found and identified, Scott said.

But, just in time for this meteor, the first cameras in a new network especially for capturing this sort of event had already been set up, and they captured shots of it on its way down - offering more clues about where it might have fallen.

The camera array project, Fireballs Aotearoa, was a joint project between the astronomy community, the University of Otago and the University of Canterbury, and aimed at setting up enough cameras across New Zealand that all of the motu would be within its range.

Scott said this meteor was captured in five of the project's cameras - one in Alexandra, one in Dunedin, one in Oamaru, and two in Southland.

Some in the network were existing cameras already operated by astronomers, but some were new.

"We only deployed some of these cameras six weeks ago, thinking we might catch something in a year's time - then all of a sudden something appears to plop down in the middle of it!

"It's stunning ... and we are confident that it dropped ... right in the middle of our network!"

Calculations done by Dr Denis Vida of the Global Meteor Network showed the meteor sped in steeply from the west travelling at about 15 km per second for more than 6 seconds, then it decelerated to about 3 km per second, before the bright light stopped.

"This is a good sign," Scott said, "because it means that meteorites survived until the end."

The cameras had supplied data that helped them to calculate it was most likely to have landed somewhere southeast of Middlemarch and west of Outram.

And the trajectory allowed them to work out it probably came from an asteroid belt of "rubble left over from early Solar System."

The camera at Dunstan High School which captured the meteor image was part of the Fireballs Aotearoa array. Photo: Supplied/ University of Otago - James Scott

Fireballs Aotearoa information released about it said keen meteorite-hunters should be careful of safety and not trespass on private property to look for it: "Don't take any risks searching for it and don't go where you shouldn't."

But, if anyone found a rock matching their description, especially in a place it looked like it did not belong, they would like to hear about it.

University of Canterbury astronomer Michele Bannister said: "Please photograph it in place, note the location using your phone GPS and avoid touching it with your bare hands (the less contamination the better). Pick it up in fresh aluminium foil if possible, or otherwise a new clean plastic bag."

Professor Scott said so far, 20 of the Fireballs Aotearoa cameras had been installed, and :"With these cameras we'd expect to see much more of these events."

Scott was coordinating the search for the rock for Fireballs Aotearoa, to reach him to report any interesting finds, email [email protected] .

Main image (Supplied/University of Otago/James Scott): A camera installed at Dunstan High School in Alexandra captured the large fireball at 10.50pm on August 28. This is a stacked image, with all other meteors also captured by the camera that night also shown. 

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