The post explores the surprising discrepancy between the estimated and observed rates of supernovae. While theoretical models predict hundreds of billions of supernovae across the observable universe annually, current surveys only detect a small fraction of that. This vast difference isn't due to faulty models, but rather the difficulty in observing these explosions. Dust, intervening galaxies, and the sheer expanse of the universe obscure the majority of supernovae from our view, making their detection a challenging endeavor despite their immense power. This explains why, even with sophisticated telescopes, we only observe a relatively tiny number compared to the predicted cosmic abundance.
The blog post "Wait. HOW MANY supernova explode every year?" by Phil Plait delves into the perplexing issue of accurately estimating the frequency of supernovae occurrences within the observable universe. The author begins by highlighting the inherent difficulty in pinning down this number due to the vastness of space and the limitations of our observational capabilities. He explains that while we can readily observe supernovae in nearby galaxies, detecting these events in more distant galaxies becomes increasingly challenging as the light from these explosions diminishes over cosmic distances. Furthermore, dust and gas within galaxies can obscure our view, making it difficult to ascertain the true number of supernovae taking place.
Plait then discusses the traditional method employed by astronomers for estimating supernova rates, which involves surveying a relatively small patch of sky for a specific period and extrapolating the findings to the entire observable universe. He points out the limitations of this method, emphasizing the inherent uncertainties and biases introduced by observing only a small portion of the cosmos. He further elaborates on the challenges posed by different types of supernovae, specifically Type Ia and core-collapse supernovae, each arising from distinct stellar evolutionary pathways and possessing unique observational characteristics.
The post proceeds to introduce a novel approach to estimating supernova rates utilizing data from the All-Sky Automated Survey for SuperNovae (ASAS-SN), a dedicated network of telescopes designed to detect transient astronomical events. This approach, as described by Plait, leverages the survey's comprehensive sky coverage to minimize the biases associated with observing only small patches of the sky. The ASAS-SN data, according to the author, suggests a significantly higher rate of supernovae than previously estimated, with potentially hundreds of billions of these stellar explosions occurring annually across the observable universe.
Plait carefully explains that this revised estimate, while seemingly astronomical, is not entirely unexpected given the sheer number of galaxies and stars contained within the observable universe. He emphasizes the significance of these findings for our understanding of stellar evolution, galactic dynamics, and the overall cosmic landscape. The post concludes by acknowledging the ongoing research in this field and the potential for future observations to further refine our understanding of supernova rates and their implications for the universe. The author highlights the dynamic nature of scientific discovery, emphasizing that our understanding of the cosmos is constantly evolving as new data becomes available and new methodologies are developed.
Summary of Comments ( 138 )
https://news.ycombinator.com/item?id=43661954
HN commenters generally expressed awe at the sheer scale of supernovae occurring in the observable universe, with some emphasizing the vastness of space this implies. Several pointed out that the article's title was misleading as it conflated observable universe numbers with those in our own galaxy, where supernovae are much rarer. One commenter highlighted the counterintuitive fact that distant supernovae, though individually fainter, are collectively brighter than those nearby due to the sheer number at those distances. There was also discussion about the accuracy of the estimates, the methodology used, and the different types of supernovae. Some users shared links to further resources and tools like a supernova simulator. A few commenters jokingly lamented the lack of easily visible supernovae from Earth.
The Hacker News post titled "Wait. HOW MANY supernova explode every year?" with the ID 43661954 has several comments discussing the surprising frequency of supernovae and the methods used to estimate them.
Several commenters express astonishment at the sheer number of supernovae occurring in the observable universe, with phrases like "mind boggling" and "absolutely insane" used. One commenter points out the vastness of space and the limitations of our observation capabilities, highlighting that we only see a small fraction of these events.
A significant thread discusses the different types of supernovae (Type Ia and core-collapse) and their respective formation mechanisms. This leads to a deeper exploration of stellar evolution, including the lifespan of stars of different masses and the eventual fates they meet. The role of white dwarfs in Type Ia supernovae is also discussed, with one commenter clarifying the distinction between novae and supernovae in this context.
There's also discussion regarding the methods astronomers use to detect and estimate the rate of supernovae, including automated surveys and the challenges of accounting for obscuration by dust and gas. One commenter mentions the use of "standard candles" like Type Ia supernovae in cosmological distance measurements and their role in the discovery of dark energy.
The challenges of defining the "observable universe" and its implications for estimating supernovae rates are also brought up. The expansion of the universe and the concept of the cosmic event horizon are mentioned, along with the idea that many supernovae are occurring beyond our observational limits.
A few commenters discuss the potential impact of a nearby supernova on Earth, considering the distances at which such an event could pose a threat. They explore the protective role of the Earth's atmosphere and magnetic field.
Finally, some commenters express a sense of wonder and awe at the scale and dynamism of the universe revealed by these statistics, reflecting on the fleeting nature of cosmic events and our place within this vast cosmic tapestry. The discussion provides a glimpse into the ongoing efforts of scientists to understand these powerful events and their significance in the evolution of the cosmos.