The latest supernovae survey reveals the crucial importance in furthering our understanding of supernovae and reaching confident conclusions as soon as possible.
The standard theory of stellar evolution results in an explosion and is revealed in a rare and beautiful astronomical event. Astronomers search for these events in the hope that they will provide greater insight into our understanding of stellar evolution. Although each supernovae event is different, specific stars will yield certain characteristics. One type of Supernovae event that is of particular interest is the type associated with a binary star system in which one of the components is a white dwarf – this is known as a Type 1a supernova. White dwarfs are extremely dense stars that have exhausted all their hydrogen and their extreme density is thus a result of them not being able to support the inward pull of gravity with the outward pressure from stellar fusion. If a white dwarf is in a binary system and able to accrete matter from its companion star, then, upon reaching a specific mass (known as the Chandrasekhar limit), its core will ignite carbon fusion which leads to an explosion – known as a Type 1a supernova. The exact theoretical details of this process are far from understood – and recent observations have now highlighted this fact.
Armin Rest and his team at the Space Science Institute in Baltimore have been studying supernova in detail and were recently given data from the Kepler space craft K2. The primary objective of the Kepler mission was to hunt for exoplanets, but with the failure of two of its four gyroscopes it has been re-purposed and is now, among other things, on the hunt for supernovae. The resulting analysis have so far revealed numerous supernovae and supernovae-like events. One intriguing such event, dubbed the Fast-Evolving Luminous Transient (FELT), has prompted new hypothesis of how stars shed their matter and evolve, as unlike typical supernovae that take a few weeks to fade, FELTs disappear in a few days.
These findings and potential further studies not only have huge implications for our understanding of stellar evolution but as well are crucial to our understanding of cosmology. Type 1a supernova are used as standard candles, much like Cepheid variables (read more here, here and here) – however beyond the local group of galaxies, telescopes do not have the resolving power necessary to observe Cepheid variables. Instead, for the farther reaches of the Universe, astronomers rely on Type 1a supernova – the rational being that the thermonuclear process that results in the supernovae will happen at the same mass and in the same way, such that the brightness observed will primarily depend on the distance. However, if these latest results are correct and the mechanism responsible for the supernova event is not consistent, not only does this highlight our lack of understanding of supernovae, it also presents a significant source of error in our determination of cosmological parameters. Scientists have already been looking to new physics to explain many discrepancies between theory and data, and now this may have to include a revised data set. Let’s hope a unified picture can come to the rescue!
Amira Val Baker