The most distant supernova discovered so far is a hypernova

The hypernova DES16C2nm in the circle (Image M. Smith / DES Collaboration)
The hypernova DES16C2nm in the circle (Image M. Smith / DES Collaboration)

An article published in “The Astrophysical Journal” describes the confirmation that the supernova DES16C2nm is the most distant ever discovered. A team of astronomers led by the University of Southampton used data collected by the Dark Energy Survey (DES) and various telescopes to study it and classify it as a superluminous supernova (SLSN) or hypernova, the brightest and most rare type of supernova. The distance of the exploded star has been estimated at about 10.5 billion light years from Earth.

DES is an international collaboration that aims to map several hundred millions of galaxies to learn more about dark energy, the force that according to the models that are most accepted but for now based on a series of hypotheses caused the acceleration of the universe expansion. The study of supernovae wasn’t part of the plans but in August 2016 it allowed to discover the one that was labeled as DES16C2nm.

The study of that supernova continued to confirm its distance and brightness. In October that result was obtained using the Very Large Telescope (VLT) and Magellan telescopes in Chile and the Keck Observatory in Hawaii with further data obtained thanks to the Gemini Observatory and the Hubble Space Telescope. This allowed to collect observations at various electromagnetic frequencies and spectroscopic data.

The conclusion of the astronomers is that DES16C2nm is a superluminous supernova, also called hypernova. According to the most accredited theory, this type of supernova is triggered by the fall of materials on a young and rapidly rotating neutron star, also called a millisecond neutron star. Basically, first there’s a supernova generated by a massive star’s explosion after which a neutron star remains: if it attracts enough materials, an explosion can be triggered with a brightness ten or more times higher than the first one.

Spectroscopic analyzes of the DES16C2nm hypernova provided various clues about its nature, also by comparison with another superluminous supernova called Gaia16apd, which showed similar characteristics. The detected spectrum contains the “signatures” of the metals produced during those explosions and the temperatures at which they occurred. These are crucial elements to understand their causes to determine if the neutron star theory is correct.

In essence, the hypernova DES16C2nm is extremely interesting for a number of reasons and the fact that it’s the most distant supernova discovered so far is almost a minor detail. Its discovery also shows that investigations such as DES could prove useful beyond the scope they were created for: Dr. Mathew Smith, the article’s first author, stated that it was exciting to be part of the investigation that discovered it while Professor Bob Nichol, another of the authors, stressed the importance of empirical science in these discoveries.

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