A new discovery has given scientists valuable insight on why some stars explode.
Cassiopeia A is a huge bubble of gas that’s been expanding since it exploded as a supernova several thousand years ago. The light from the explosion first reached Earth in the 1670s.
Scientists have been studying the dead star, which is around 11,000 light years away, for the past 20 years using NASA's Chandra X-ray Observatory.
Results published in the scientific journey Nature this week reveal that bubbles of titanium are floating in Cassiopeia A – giving new insight into how the titanic explosions take place.
"Scientists think most of the titanium that is used in our daily lives – such as in electronics or jewellery – is produced in a massive star's explosion," lead study author Toshiki Sato, an assistant professor in the department of physics at Rikkyo University in Tokyo, wrote in a statement.
"However," he added, "until now scientists have never been able to capture the moment just after stable titanium is made."
The element is created when a massive star – perhaps 10 times the size of our Sun – runs out of nuclear fuel and collapses into a black hole or an ultra-dense object called a neutron star.
The birth of a neutron star creates heavy elements such as gold and titanium – but until very recently astronomers weren’t completely sure how the process occurs.
When scientists modelled the phenomenon, they found that the explosions would burn themselves out before reaching full power.
They now believe that neutrinos – ghostly particles that can pass through an entire planet without stopping even slowing down – could be the missing link that makes the explosions continue to happen.
The detection of the titanium bubbles is an important clue.
Using the Chandra X-ray telescope the astronomers analysed long finger-like structures made of titanium, chromium and iron that point away from the site of the ancient explosion, suggesting that the elements were produced deep in the heart of the dying star.
"We have never seen this signature of titanium bubbles in a supernova remnant before, a result that was only possible with Chandra's incredibly sharp images," said Sato’s colleague Keiichi Maeda.
"Our result is an important step in solving the problem of how these stars explode as supernovae.”
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