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We argue that type Ia supernovae (SNe Ia) are the result of head-on collisions of White Dwarfs (WDs) in
triple systems. The thermonuclear explosions resulting from the zero-impact-parameter collisions of WDs
are calculated from first principles by using 2D hydrodynamical simulations. Collisions of typical WDs with
masses 0.5-0.9 Msun result in explosions that synthesize 56Ni masses in the range of 0.15-0.8M Msun, spanning the wide distribution of yields observed for the majority of SNe Ia. The robustness of the shock ignition process is verified with a detailed study using a one-dimensional toy model and analytic tools. The late-time (& 50 days after peak) bolometric light curve is equal to the instantaneous energy deposition and is calculated exactly, by solving the transport of gmma-rays emitted by the decay of 56Ni using a Monte-Carlo code. All collisions are found to have the same late-time light curves, when normalized to the amount of synthesized 56Ni. This universal light curve is shown to agree with the majority of the supernovae in the compilation made by M. Stritzinger to an accuracy of better than 30% in the range 40 < t < 80 days after bolometric peak. The widths of the 56Ni mass- weighted-line-of-sight velocity distributions are correlated with the 56Ni yield and in agreement with the observed Mazzali relation. The continuous distribution of observed SN Ia features, is naturally reproduced with the distribution of WD masses involved in the collisions.

Empathy, the recognition and sharing of affective states between individuals, is an adaptive response with ancient evolutionary roots. The experience of empathy rises from activation of subcortical neural circuits in the brain stem, thalamus and paralimbic areas that are highly conserved across mammalian species. Primarily, it is crucial for the survival of altricial mammals to be able to respond to the needs of offspring appropriately. More broadly, communication of emotions promotes group survival, by alerting against potential threats and, depending on context, inducing pro-social actions. Behavioral homologues of empathy have been observed in different non-human animals. For instance, it has been clearly established that rodents display emotional contagion of others&#8217; distress, and are motivated to alleviate another rat&#8217;s distress. We found that rats intentionally released a cagemate trapped in a restrainer, even when social contact was prevented. When a second restrainer containing a highly palatable food (chocolate chips) was present, rats opened both restrainers and typically shared the chocolate. Since only cagemates were tested, it is unclear if these behaviors generalize to strangers. Helping others is costly and resource depleting, and should thus be discriminately extended. In humans, the expression of empathically motivated pro-social behavior is dependent on social context, where people are more motivated to help in-group members than out-group members. Correspondingly, emotional contagion is modulated by familiarity in rodents. Mice have been found to display heightened pain sensitivity when witnessing a cagemate in pain, but not a stranger in pain. To investigate these questions, we are currently exploring the effect of social parameters such as familiarity and relatedness on the expression of empathic helping in rats.