An astronomical study reveals thatone in five supernovae that explode in nearby galaxies go unnoticed in optical studies, a rate that increases up tofour out of five in the case of distant galaxies. The research, published in the journalThe Astrophysical Journaland in which the Spanish Miguel Ángel Pérez-Torres, from the Institute of Astrophysics of Andalusia (IAA-CSIC) participates, agrees with the star formation rate that astronomers handle and that had been discussed in previous works.
Stars with more than eight times the mass of the Sun, known as massive stars, are the fundamental component of the global stellar luminosity of galaxies and are a tool for understanding how and at what rate stars form. However,its study is complicated by the darkening by dust of the central regions of galaxies, where the stellar birth rate is concentrated.
A solution to this problem lies in the study of one of the last stages of its life: supernova explosions. “The number of massive stars that explode in the form of a supernova must be equivalent to that of massive stars that are born”, pointed out the Finnish Seppo Mattila, first author of the work. Thus, the count of the number of supernovae is a tracer of the rate of massive star formation and can even be used to determine the total rate of star formation.
A necessary tool, because just over a year ago a study was published that suggested that the rate of star formation throughout the history of the universe was approximately half of what was theoretically expected. “With this work we show that there is not really a problem with the rate of supernovae: when you take into account the number of supernovae that cannot be detected due to the huge amount of dust that exists in the central regions of these galaxies, the numbers they marry very well with theoretical predictions “, points out Miguel Ángel Pérez-Torres.
To determine the percentage of “lost” supernovae, the astronomers considered the scenarios where star formation is concentrated: in the near universe it occurs mainly in normal galaxies with high dust content, while in the distant universe it clumps together in a specific type of galaxies, the luminous and ultra-luminous galaxies in the infrared (known as LIRG and ULIRG, for their English names). Thus they obtained the percentages of 20% and 80% of unobserved supernovae.
