The glowing embers left behind by one of the most powerful type of explosions in the Universe have been revealed for the first time.
Remnants from giant fireballs unleashed by a supernova are still glowing at temperatures 10,000 times hotter than the Sun thousands of years after the event.
They were captured by the Japanese Suzaku space observatory, after unusual features were detected in the Jellyfish Nebula (IC 443), 5,000 light years away.
Suzaku detected X-rays from fully ionized silicon and sulfur - which indicates temperatures of 17million celsius
The strange phenomenon was picked up in the x-ray spectrum, so the satellite, which studies such forms of electromagnetic radiation, was best placed to study it.
A supernova remnant usually cools quickly due to rapid expansion following the explosion. Then, as it sweeps up tenuous interstellar gas over thousands of years, the remnant gradually heats up again.
But Suzaku's X-ray Imaging Spectrometers were able to separate the x-rays by energy in much the same way as a prism separates light into a rainbow of colours.
This allowed astronomers to tease out the different processes that occur in the remnant over time.
Suzaku found another fossil fireball in the supernova remnant W49B. It detected X-rays produced when heavily ionized iron atoms recapture an electron. This view combines infrared images from the ground (red, green) with X-ray data from Nasa's Chandra X-Ray Observatory (blue).
They found evidence in the Suzaku spectrum that indicated large amounts of silicon and sulfur atoms from which all electrons had been stripped away. This requires temperatures higher than 17million celsius and so could only have been created immediately after the supernova explosion.
'Suzaku sees the Jellyfish's hot heart,' team member Midori Ozawa said.
