Cesium-137 is a radioactive isotope of the element cesium, with a half-life of about 30.1 years. It is produced during nuclear fission processes, such as those occurring in nuclear reactors and during atomic bomb explosions. Due to its radioactive properties, cesium-137 emits beta particles and gamma radiation, making it useful in various applications, including medical treatments and industrial gauges. In medicine, cesium-137 is used in radiotherapy to treat certain types of cancer, as it can target and destroy malignant cells. Additionally, it is employed in radiological imaging and as a tracer in environmental studies to track the movement of materials in ecosystems.