New calculations indicate that mixing of neutrinos occurs in the context of neutron star mergers. This interaction drastically alters the fundamental nature of these incredible cosmic occurrences. Neutrinos, fundamental particles known for their weak interactions with other matter, come in three distinct flavors: electron, muon, and tau. As we mentioned in a previous post, a neutrino’s flavor can change, affecting how it interacts with matter around it. In the wake of neutron star mergers, this change is fundamental.
Neutron stars are the finely-tuned remnants of massive stars that have exploded in supernova explosions, leaving these incredibly dense celestial-sized bodies behind. When two neutron stars merge, they produce a rich and diverse spectrum of detectable signals on Earth. This unexpectedly important role of neutrino mixing in these mergers raises exciting questions. We are still very much interested in the nature and fate of these merger telltales and their ability to forge the heaviest ingredients.
Understanding Neutrinos and Their Flavors
Neutrinos are special among subatomic particles because they barely interact with everyday matter. Their capacity to swap flavors on-the-fly during interactions is often key to their roles and effects in their high-energy worlds. For example, with their weak interactions, the electron-type neutrinos can convert a neutron into a proton and an electron, showcasing their transformative power.
To illustrate how these processes are important, we turn to David Radice, an astrophysicist at Princeton University. He states, “A neutrino’s flavor changes how it interacts with other matter.” This interaction is especially crucial during neutron star mergers, a scenario in which the astrophysics is already complicated and multidisciplinary.
Prior simulations of binary neutron star mergers had not included these flavor changes. Consequently, scholars have had an incomplete picture of how neutrino mixing affects the neutron star merger as a whole. Yi Qiu, a researcher involved in the recent simulations, notes, “Previous simulations of binary neutron star mergers have not included the transformation of neutrino flavor.”
Impacts on Merger Dynamics and Element Formation
The recent OSU findings show that neutrino mixing in neutron star mergers plays a pivotal role. The dynamic behavior of neutrons within the system is tremendously altered. This change has important implications for the total amount and properties of matter ejected during the merger. This ejected material continues to capture neutrons and processes them into much heavier elements. Among them are resources critical to our economy, including gold, platinum and rare earth elements found nowhere else.
Qiu elaborates on these findings, stating, “So, the conversion of neutrino flavors can alter how many neutrons are available in the system, which directly impacts the creation of heavy metals and rare earth elements.” Here’s why he thinks these findings are groundbreaking. In his new method, including for neutrino mixing makes it possible to increase the production of heavy elements by a factor of ten.
The merger dynamics produces electromagnetic emissions and possibly gravitational waves produced during such events. Radice remarks, “In our simulations, neutrino mixing impacted the electromagnetic emissions from neutron star mergers and possibly the gravitational waves as well.” This illustrates the unity between different physical processes happening in these cosmic wrecks.
Future Research and Observational Opportunities
As theoretical particle physics continues to develop, researchers hope to improve their simulations to fold neutrino transformations into their framework in more realistic ways. Big questions still hang over where and in what manner these transformations take place inside neutron star mergers. Qiu acknowledges this challenge by stating, “There’s still a lot we don’t know about the theoretical physics of these neutrino transformations.”
If we get some observational opportunities, it would give us some very important insights into these cosmic events. The advanced detectors LIGO, Virgo and KAGRA are constantly improving their detection capabilities. Because of this, astronomers are poised to detect gravitational waves at an unprecedented rate. Radice points out that this progress will aid in interpreting future observations by better understanding how emissions arise from neutron star mergers.
He states, > “With cutting-edge detectors like LIGO, Virgo and KAGRA and their next-generation counterparts… astronomers are poised to detect gravitational waves more often than we have before.” This new development highlights the need to incorporate neutrino mixing into new models. In this way, we’re better able to make causal conclusions from the data that we observe.