SNRs

SNRs is an acronym that can refer to two major concepts in science and engineering. In astronomy, SNRs stands for supernova remnants, the expanding shells of gas and dust left behind after a supernova explosion. These objects interact with the surrounding interstellar medium, producing emission across the electromagnetic spectrum—from radio and optical to X-ray and gamma-ray. The shocks generated by the explosion accelerate particles and contribute to the chemical enrichment of galaxies. SNRs exhibit diverse morphologies: shell-type remnants whose emission comes mainly from the expanding shell, plerionic or Crab-like remnants powered by a central pulsar wind nebula, and mixed-morphology remnants with differing radio and X-ray appearances. Evolution proceeds through stages such as free expansion, the Sedov-Taylor (adiabatic) phase, and a radiative phase as the remnant slows and cools. Studied for insights into nucleosynthesis, cosmic ray acceleration, and galactic dynamics, SNRs serve as laboratories for high-energy processes and the history of their host galaxies.

SNRs also stands for signal-to-noise ratio, a measure used in signal processing, communications, and data analysis. It is the ratio of the power or amplitude of the desired signal to that of the background noise. Common definitions include SNR = P_signal / P_noise or SNR expressed in decibels as 10 log10(P_signal/P_noise). A higher SNR indicates a clearer, more reliable signal, while a low SNR implies that noise dominates. SNR influences the accuracy of measurements, required exposure or integration time, and the achievable data rates in communications. Techniques to improve SNR include longer integration, averaging, filtering, and improved detector design.