The shockwave generated by the explosion of an ageing giant star has been observed by an international team of astronomers.
The discovery, accepted for publishing in the Astrophysical Journal, will help scientists understand the life cycle of stars, said study co-author Brad Tucker of the Australian National University.
"This is the first time we've seen this in the normal visible colours, and we now know it happens," Dr Tucker said.
"The fundamental way we believe that core collapse happens is related to this shockwave happening. So the physics has been around ... for decades and we've finally now been able to physically examine and test what's going on."
The team of scientists observed the earliest moments of two old stars exploding using the Kepler Space Telescope.
They spotted the shockwave around the smaller of the two stars - a red supergiant over 270 times the radius of the Sun and 750 million light years away.
As the star ran out of fuel it began collapsing and compressing on its central core.
"It's like packing in dirt," Dr Tucker said. "You keep pressing it till it's so dense you can't get it in anymore, and that's when you create a neutron star.
"But you reach a limit when you can't pack it in anymore, and that force pushing in bounces back and it triggers a shockwave to go through the star, causing the star to actually blow up."
That's the moment the supernova starts creating the heavier elements on the periodic table, such as gold, silver and platinum.
"It's that singular moment when we can see the periodic table happening, when we can see the process of creating these new elements, and also see a switch from fission to fusion all at the same time because of this residual shockwave going through this star," Dr Tucker said.
The shockwave that initiated the core collapse or type IIp supernova was seen as a quick brightening - or flash. The supernova itself also creates a brightening, but this fades over a longer period of time.
Because the shockwave doesn't last very long - typically hours to days - it's been a challenge to catch one.
Scientists have previously observed a shockwave in X-ray (as opposed to visible light) but that was just pure luck, Dr Tucker said.
"They were actually looking at another exploding star and one happened to go right off in the exact patch of sky in the exact moment they were looking at it. It was the definition of luck."