anomalous

In 2023, the Zwicky Transient Facility, an astronomical consortium led by Caltech, detected a curious signal on the outskirts of a dwarf galaxy 1.3 billion light years away. At first everything seemed to indicate that it was the result of a type II supernova explosion. It’s always interesting to spot one, but it’s not unusual. However, as soon as they tried to classify it a little better, they realized that it had many qualities that did not fit within the definition of this phenomenon. Investigating, they discovered that, in reality, the signal corresponds to one of the rarest explosions that occur in the Universe: a pairwise instability supernova. A special supernova. Pairwise instability supernovae are supernova explosions that occur when the original star is very massive and is in an environment with low metallicity. Furthermore, there is another big difference. After a typical supernova explosion, either a neutron star or a black hole usually forms. In this case, however, it can be said that the stars completely self-destruct, without leaving any remnants. It is a very rare phenomenon, very difficult to detect. However, the authors of the study that has just been published hope, with what they have learned from this finding, to locate other similar events based on the data obtained with the Vera Rubin Observatory. The brightness curve that didn’t add up. Normally, when a normal supernova explosion occurs, the brightness curve is plateau-shaped. On the other hand, in this event, named SN 2023vbw, after an initial cooling, a constant increase in brightness was observed until reaching a very bright peak around 190 days. Then, until day 230, the brightness began to decrease and finally stabilized on a plateau. Other data that did not add up. The total irradiation energy of this phenomenon was 3× 1050 Ergs, a figure that is more than 10 times higher than that of a type II supernova. Furthermore, during ascent, the explosion stabilized at a nearly constant temperature while its outer shell continued to expand. For this to occur there must be a large and continuous internal heating source, which does not happen with a type II supernova. On the other hand, as the supernova faded, the emissions that were detected had nothing to do with those normal for a conventional supernova. Finally, the kinetic energy was 60 to 130 times greater than the maximum energy that an ordinary supernova can produce. Two very different supernovae. Normally, a very massive star is subject to two very powerful forces. On the one hand, that of gravity, which compresses it inward. On the other hand, that of radiation, which pushes outwards. Both forces remain in balance. However, when the star runs out of fuel to stay “on,” the radiation pressure decreases, so gravity pushes strongly inward. As a result, the star collapses, leading to a supernova explosion. Behind it a black hole or a neutron star can form. If the star is very massive and is also located in an environment with low metallicity, the process is slightly different. To begin with, such high temperatures are reached in its core that enough energy is generated for the photons to transform into an electron-positron pair. This phenomenon eliminates the pressure exerted by radiation much more suddenly, so that the force exerted by gravity, which is immense, causes the collapse of the star and, later, a very violent explosion. So violent that everything is destroyed, there is no remnant left. The location of SN 2023vbw (magenta circle) on the outskirts of its dwarf host galaxy (green circle). The role of metallicity. The low metallicity of the environment helps because metals normally absorb the radiation coming out of the star, favoring the expulsion of matter outward. If there are few metals, less matter will be extracted from the star and the greater its mass. A blue supergiant in an environment with very low metallicity. The light curves that were detected seem to correspond to a blue supergiant as a starting point. This very massive star, which can be caused by the merger of two stars in a binary system, can give rise to a type II supernova. However, we have already seen that the characteristics do not add up. However, the scientists who analyzed the results found the clue they were missing. That the explosion had occurred in an environment with very low metallicity. It corresponded approximately to a tenth of that of the Sun. It is the missing ingredient for a pairwise instability supernova to occur. A very rare phenomenon. This phenomenon is one of the rarest explosions that occur in the Universe. There are many very massive stars, but in general they are in very metal-rich environments, so a pairwise instability supernova cannot occur. Therefore, this discovery is very exciting. Although it may soon become more common. And not only because of the Vera Rubin Observatory that we have already mentioned. It is also expected that the brand new Nancy Grace Roman from NASA can detect more phenomena of this type when you start doing your work. Until then, detecting stars self-destructing in this way will remain even more difficult than finding a needle in a haystack. Image | Supernova remnant on cover. Credit: NASA/CXC/Rutgers/G.Cassam-Chenaï, J.Hughes et al.; Radio: NRAO/AUI/NSF/GBT/VLA/Dyer, Maddalena & Cornwell; Optical: Middlebury College/F.Winkler, NOAO/AURA/NSF/CTIO Schmidt & DSS | Hiramatsu et al. In Xataka | Caltech has published the “strongest evidence yet” that an unknown planet exists in the solar system