An international team with the participation of the Higher Council for Scientific Research (CSIC) has observed the early stages of a supernova. The snapshot, which collects three different moments within a few hours of the stellar explosion, corresponds to a star that was 500 times larger than the Sun and that exploded 11,000 million years ago, when the universe was still primitive. This image, captured by NASA’s Hubble Space Telescope and the European Space Agency (ESA), has been published in the magazine ‘Nature’.
This is the first time that a supernova in its early stages has been observed with such precision at this distance and, moreover, corresponds to a stellar explosion at the beginning of the history of the universe. Both findings could help the scientific community learn more about the formation of stars and galaxies in the early universe.
“It is quite rare that a supernova can be detected at a very early stage, because that stage is so short,” explains Wenlei Chen, first author of the paper and a researcher in the School of Physics and Astronomy at the University of Minnesota. “It only lasts a few hours to a few days, and it can easily go unnoticed even for early detection. In the same exposure, we were able to see a sequence of images, like the multiple stages of a supernova”, he adds.
The Hubble telescope has captured in a single image three unique moments of the supernova explosion throughout different phases, which reached Earth at the same time. This image has been achieved thanks to the phenomenon called gravitational lens: when a cluster of galaxies, with a mass thousands of times the mass of our galaxy, amplifies the light that is produced by objects that are far away and aligned just behind the cluster. It works like a lens would, magnifying the light that reaches us from the supernova, making it visible to the space telescope.
In this way, the galaxy cluster Abell 370 has acted as if it were the lens, magnifying the light of the distant supernova, which was located behind the cluster. Images magnified by this lens have taken three different routes through the cluster, due to length differences in the paths taken by the light from the supernova, the slowing down of time, and the curvature of space by gravity predicted by Albert Einstein. .
Image captured by the Hubble telescope showing the three phases of the supernova explosion behind the galaxy cluster ‘Abell 370’
“Because light takes different times to travel down these three paths, the Hubble image shows three instants of the explosion in a single image. Among these three instants, one of them corresponds to only a few hours after the explosion”, explains José María Diego, a researcher at the Institute of Physics of Cantabria (IFCA, CSIC-UC).
In addition, the telescope has captured the changes in temperature of the supernova, which are observed with the variation in its color. The bluer it is, the hotter the supernova, and as its light cools, it becomes redder. “You see different colors in all three images,” says Patrick Kelly, study leader and professor in the University of Minnesota School of Physics and Astronomy. “In the core of the massive star there is a shock, it heats up, and then you see that it cools down. It is probably one of the most amazing things I have ever seen », he points out.
a giant star
The observations show that the red supergiant star was 500 times larger than the Sun. This is the first time that the research team has been able to measure the dimensions of a dying star in the earliest universe. To achieve this, they have relied on machine learning algorithms to measure the star’s brightness and cooling rate.
Now, taking advantage of the launch of NASA’s James Webb Space Telescope, the team plans to begin observing supernovae even further away and create a catalog of supernovae that will help understand whether stars that existed billions of years ago are different from those of the universe we know today.