The “renegade” star explosion has never before been witnessed and is set to revise our understanding of how most massive stars die. Although the European Space Agency’s (ESA) Gaia satellite first noticed the SN 2016iet supernova lost three years ago, intensive follow-up observations concerning the cosmic object’s distance and composition have only just finished. Professor Edo Berger, of the Harvard-Smithsonian Centre for Astrophysics, said: “The Gemini data provided a deeper look at the supernova than any of our other observations. “This allowed us to study SN 2016iet more than 800 days after its discovery, when it had dimmed to one-hundredth of its peak brightness.”
Chris Davis, program director at the National Science Foundation (NSF), added, “These remarkable Gemini North telescope observations demonstrate the importance of studying the ever-changing Universe.
The Gemini North telescope data provided a deeper look at the supernova than any of our other observations
“Searching the skies for sudden explosive events, quickly observing them and, just as importantly, being able to monitor them over days, weeks, months, and sometimes even years is critical to getting the whole picture.
“In just a few years, NSF’s Large Synoptic Survey Telescope will uncover thousands of these events, and Gemini is well positioned to do the crucial follow-up work.”
The Gaia satellite data revealed only weak hydrogen emission at the supernova’s location, suggesting the original star of SN 2016iet lived in an isolated region with very little star formation – an unusual environment for such a massive star.
Supernova explosion: The event forces us to revise our understanding of how most massive stars die
Supernova explosion: Some massive star cores collapse into a neutron stars or black holes
Professor Berger added: “Despite looking for decades at thousands of supernovae, this one looks different than anything we have ever seen before.
“We sometimes see supernovae that are unusual in one respect, but otherwise are normal; this one is unique in every possible way.”
SN 2016iet has a multitude of oddities, including its incredibly long duration, large energy, unusual chemical fingerprints, and environment poor in heavier elements — for which no obvious analogues exist in the astronomical literature.
Sebastian Gomez, also of the Centre for Astrophysics, and lead author of the investigation, said “When we first realised how thoroughly unusual SN 2016iet is, my reaction was ‘Whoa – did something go horribly wrong with our data?’”
The supernova’s bizarre nature suggests it began its life as a star boasting 200 times the mass of our Sun — making it one of the most massive and powerful single star explosions ever observed.
Growing scientific evidence indicates the first stars born in the nascent Universe may have been just as massive.
Astronomers predicted that if such behemoths retain their mass throughout their relatively brief life of a few million years, they will die as pair-instability supernovae, which derives its name from matter-antimatter pairs formed in the explosion.
Most massive stars end their lives in a cosmically cataclysmic event, spewing matter rich in heavy metals into space, while their core collapses into a neutron star or black hole.
But pair-instability supernovae are a different breed. The collapsing core produces copious gamma-ray radiation, leading to a runaway production of particle and antiparticle pairs that eventually trigger a catastrophic thermonuclear explosion that annihilates the entire star, including the core.
Supernova explosion: he European Space Agency’s (ESA) Gaia satellite spotted SN 2016iet 3 years ago
Supernova explosion: The violent event was unlike anything ever witnessed before
Models of pair-instability supernovae predict they will occur in environments poor in elements heavier than hydrogen and helium, such as dwarf galaxies and the early Universe — and the team discovered just that.
The event occurred at a distance of one billion light years in a previously uncatalogued dwarf galaxy poor in metals.
Mr Gomez added: “This is the first supernova in which the mass and metal content of the exploding star are in the range predicted by theoretical models.
Another surprising feature is SN 2016iet’s stark location.
Most massive stars are born in dense clusters of stars, but the supernova in question formed in isolation some 54,000 light years away from its dwarf host galaxy’s centre.