An international team of scientists led by Yuan Qi Ni of the Dunlap Institute, University of Toronto, has found the youngest supernova type Ia to-date, barely an hour after the first light of the explosion, which is a world record in discoveries so far. These results, that include the participation of Santiago González-Gaitán from CENTRA-IST, are included in the article “Infant-phase reddening by surface Fe-peak elements in a normal type Ia supernova” published in Nature Astronomy, on February 17.
The supernova named “SN 2018aoz” exploded on the 29th of March 2018. The scientific team detected it just an hour after the first light of its explosion. Supernovae are dramatic explosions of stars at the end of their lives, and type Ia supernovae are a subset of these, consisting of thermonuclear explosions originating from white dwarfs in binary systems. These supernovae are essential to understand the origin of the heavy elements in the Universe and they are crucial to measure distances and the accelerated expansion of the Universe.
Despite their importance, numerous questions remain on the nature of the binary system where they are born as well as the explosion mechanisms. Observing supernovae at the earliest moments of their existence is key to unveil some of these mysteries, but it is technically very challenging since we do not know a priori where a supernova will explode and its luminosity is very weak during the first days. In this context, the researchers Yuan Qi Ni, Dae-Sik Moon and Maria R. Drout, from the Dunlap Institute of the University of Toronto, have led an international programme to discover the youngest supernovae and study them deeply throughout their evolution.
Using the KMTNet (Korea Microlensing Telescope Network), a net of three telescopes located in Chile, South Africa and Australia, that provide 24h dark sky coverage, the research team has catched the first moments of the birth of a type Ia supernova. The KMTNet telescope array facilitates such searches with a network of three identical telescopes around the globe that permit continuous 24h search and follow-up of astronomical transients. “It is very important to take repeated images of the same portions of the sky with high frequency in order to detect young supernovae. KMTNet can take images of many galaxies every 4-5 hours continuously, which is a formidable accomplishment”, says the CENTRA researcher.
A fast reddening of the light in the first hours
The earliest detections of SN 2018aoz in the multiple filters reveal a very red distribution of light during the first twelve hours of its infant life. This indicates that the blue portion of the emission is being absorbed by a concentration of iron-like metals in the outer 1% layer of the material ejected by the exploding star.
This discovery points towards an early burning of material into heavy elements directly on the surface, or alternatively a process in which burned heavy elements from the center are mixed towards the outskirts flourishing then on the surface.
These observations mark a milestone in the understanding of the explosion mechanism of type Ia supernovae. As Santiago González points out “we knew that these explosions generate many heavy elements”, but it had not yet been proved “which type of stars explode this way and the type of explosion”. “We knew that a white dwarf explodes in a binary system, but the models and theories were based on a companion star and on the explosion mechanism”.
The CENTRA researcher contributed from the beginning of the survey with a significant amount of observing time making the search strategy more successful. “This is really important, because to detect very young supernovae, you have to look at the same area of the sky, the same galaxies, many times”, he stresses. “I am very happy to see the result of our efforts! It’s amazing!”, adds the scientist.
