An ancient supernova seen at 3 different points in space

A supernova is a stellar explosion, which occurs at the end of the life of some very massive stars. In this violent epilogue, the star ejects the material from its outer layers by means of a shock wave, which allows us to see the different elements of which it was composed.

An international team, in which Tom Broadhurst, Ikerbasque Researcher from the University of the Basque Country (UPV/EHU) and associate of the DIPC (Donostia International Physics Center), has taken part, has obtained three images, each one in a different place and from a different color, of the same supernova in the distant universe, thanks to the lens-like amplifying power exerted by a galaxy located in the foreground.

The research team developed a model of the galaxy’s gravitational field that served as a lens and thus it was possible to determine that the light from these three images traveled three different paths, which differ in distance by a few days. This explains the three colors obtained in the images, since as the supernova gas expands and cools, there is a variation in the color emitted. At higher temperatures, the emitted light is bluer, and as the temperature decreases, the emitted light tends to red. Thus, the blue image corresponds to a photograph of the supernova a few hours after the stellar explosion, while the green and red images correspond to 2 and 8 days after the explosion, respectively.

This information made it possible to determine the radius of the star that exploded, a red supergiant with a radius comparable to 500 times that of the Sun, and which exploded 11.5 billion years ago, long before the Earth was born and just when our galaxy was being formed. . Images of this supernova, captured with the Hubble Space Telescope, are greatly magnified by the gravitational field of a nearby galaxy that acts as a lens, allowing one to see much farther in distance, and in time.

The 3 areas where the supernova was sighted. (Image: Science / NASA / ESA / STScI / Wenlei Chen (UMN) / Patrick Kelly (UMN) / Hubble Frontier Fields)

The study of the explosions of these red supergiant stars fits with the current idea of ​​how the heavier atomic elements were created inside the stars and during the supernovae explosions: the elements forged inside the stars are released in these explosions of supernova, to become the next generation of gas and material from which solar systems and life as we know it are created. Without these explosions, the gas in present-day galaxies would only include the hydrogen and helium that formed in the Big Bang and would not support complex life that requires other, heavier chemical elements. Furthermore, this supernova observed through gravitational lensing demonstrates that an event occurring in the distant Universe can be witnessed multiple times, so in principle we could focus our instruments ahead of time to see in detail the eruption of a star that is falling. turns into a supernova.

The study is titled “Shock cooling of a red super-giant supernova at redshift 3, in lensed images”. And it has been published in the academic journal Nature. (Source: UPV/EHU)