Astrophysicists have simulated the evolution of the Universe with a dark energy density value several tens of times greater than observed. It turned out that the stars in galaxies in this case are located much closer, because of which life on the planet with a high degree of probability will be destroyed by a nearby supernova explosion. The results are presented in the preprint at arXiv.org.
Dark energy is a hypothetical form of energy responsible for the observed accelerated expansion of the universe. According to modern observations, it corresponds to about 70% of all the energy in the universe in the current epoch. One of the most popular explanations among scientists is that dark energy is the energy of the vacuum itself. If so, then modern quantum mechanics predicts that the density of dark energy should be at least 120 orders of magnitude greater than observed. However, such strong dark energy would cause the universe to expand too quickly in the early stages and lack structures such as stars and galaxies.
In previous studies, a team of Japanese astrophysicists led by Tomonori Totani of the University of Tokyo simulated universes with different values of dark energy density. It turned out that galaxies, stars and habitable planets can appear at a density 20-50 times higher than the observed one. In the new work, they decided to consider in detail the option with the most dense dark energy. In this case, galaxies appear only at the earliest stages of evolution, and the stars in them are located about 10 times closer than in the Milky Way. As a result, suitable planets in such a universe will be sterilized by high-energy radiation from nearby supernovae, which will flare up much more often than in our Galaxy.
“This forms a new connection between dark energy and astrobiology, which were previously considered completely different fields of study,” says Totani. However, other scholars draw attention to important simplifications made in this work. In particular, the main damaging factor of supernovae is the most severe gamma radiation, but in the case of ordinary supernovae it accounts for only a small part of the total explosion energy, which is why they are not very effective sterilizers. Events of a rare subclass of supernovae, gamma-ray bursts, do the best with this task. The discussed work did not take into account the rarity of gamma-ray bursts, which may somewhat exaggerate the degree of the detected effect.