The James-Webb delves into the secrets of supernovae
The James-Webb is beginning to take over from the Hubble telescope by renewing our study of supernovae and the nucleosynthesis processes it enables. Remember that these explosions inject into the interstellar medium nuclei of oxygen, nitrogen and carbon but also of iron, nuclei that the Big Bang had not produced and which are the basis of the molecules of living things.
Star explosions have fascinated astronomers and astrophysicists at least since the heroic times of the “ sky builders ” (notably Tycho Brahe and Johannes Kepler) to use the terms of Jean-Pierre Luminet. They did not know at all then what these new stars were, these stellae novae suddenly appeared on the celestial vault. It will be necessary to wait for the XX E century with the developments of quantum physics and nuclear physics so that the members of the noosphere make the distinction between nova and supernova on the one hand, then between supernova of type SN II and supernova of type SN Ia on the other hand, first from an observational and then a theoretical point of view.
One of the leading articles concerning the nature of SN Ia dates back to 1960 and is due to Fred Hoyle and William Fowler. The two researchers understood that we were in the presence of thermonuclear explosions of white dwarf stars containing essentially a carbon-oxygen mixture. One of the by-products of these cosmic explosions that can be seen billions of light-years away as they are so bright are the iron nuclei found in our red blood cells and in the Earth's core.
this image from hubble shows ngc 1566, a beautiful galaxy located about 40 million light-years away in the constellation dorade. ngc 1566, sometimes also called spanish dancer, is an intermediate spiral galaxy, which means that while it does not have a well-defined region of bar-shaped stars at its center—like barred spirals—it is also not quite an unbarred spiral. the small but extremely bright core of ngc 1566 is clearly visible in this image, a telltale sign that it belongs to the seyfert class of galaxies. the centers of these galaxies are very active and bright, emitting strong bursts of radiation and harboring supermassive black holes that are several million times the mass of the sun. ngc 1566 is not just any seyfert galaxy; it is the second brightest known seyfert galaxy.
esa, nasaExplosions that produce radioactive elements
These cosmic beacons are also used to study the accelerating expansion of the observable Universe and shed light on the nature of what we call dark energy , and they haven't given up all their secrets.
Luckily, the noosphere has a new eye in orbit and it's starting to look into those secrets. You guessed it, it is the James-Webb telescope, which ultimately only takes over from its predecessor, the Hubble telescope, for the same kind of research.
In this case, an international team of researchers has dedicated its efforts to studying the remains of SN 2021aefx, an SN Ia type supernova whose explosion was detected in November 2021. As explained in the article published in The Astrophysical Journal Letters about it, the event occurred in the Seyfert-like spiral galaxy NGC 1566 — also known as the “Spanish Dancer” — located about 40 million light-years from the Way milky way towards the Constellation of the Dorade.
The JWST observations were made almost a year after the explosion of SN 2021aefx and in the infrared. As Michael Tucker, researcher at the Center for Cosmology and AstroParticle Physics , reminds us in a press release from the Ohio State University : " Explosions of white dwarfs are important in the field of cosmology because astronomers often use them as indicators distance. They also produce many of the iron group elements in the Universe, such as iron, cobalt and nickel .
Indeed, the explosion first produces a radioactive isotope of nickel which rapidly disintegrates in the form of an isotope that is also unstable of cobalt according to the reaction 56 Ni → 56 Co. Another reaction then occurs in a cascade 56 Co → 56 Fe. The energy released and the particles accompanying these disintegrations then circulate in the ejecta of matter produced by the explosion, itself immersed in magnetic fields.
a false color view of ngc 1566 taken by jwst. the remnants of supernova sn 2021aefx are in the green circle. the black bar gives the distances in kiloparsec. a parsec is 3.26 light years.
ness mayker chen et al. , 2023 apjlA key to validating the chemical evolution of galaxies
Michael Tucker and his colleagues were just busy studying NGC 1566 to better understand in general how certain chemical elements are emitted into the surrounding cosmos after an explosion when they happened to realize that the JWST images could give information about the supernova SN 2021aefx. Understanding how these stellar reactions affect the distribution of iron elements in the cosmos can give nuclear astrophysicists and cosmochemists deeper insight into the chemical evolution of galaxies. It is still necessary to understand all the mechanisms at work.
As the Ohio State University release explains , near-infrared and mid-infrared observations from the JWST clarified what was happening with the decay of cobalt-56 to iron-56. The theory had been predicting for a while that, if the nuclei were going to end up in fine in the interstellar medium, the energy released by this type of reaction should remain confined in the nebula formed by the ejecta of matter from the explosion.
“ This is one of those studies where, if our results were not what we expected, it would have been really concerning. We've always assumed energy doesn't leak from ejecta, but until the JWST, that was just a theory. This study validates almost 20 years of science. It doesn't answer all the questions, but it does a good job of at least showing that our assumptions weren't catastrophically wrong ,” Tucker said.
The results obtained therefore support the model in which the magnetic fields in the material of the star blown up by the SN Ia type explosion retain a large part of the energy produced by the decay of the cobalt isotopes.
“ The power of JWST is truly unprecedented. It's really promising that we're doing this kind of science, and with JWST there's a good chance that we can not only do the same thing for different types of supernovae, but do it even better,” concludes Michael Tucker .
Source : websites