Actinium-226 is a radioactive isotope of the element actinium, which has the atomic number 89. It is produced through the decay of thorium-230 and is part of the uranium-235 decay series. Actinium-226 has a half-life of about 29.37 hours, meaning it takes this amount of time for half of a sample to decay into other elements. This isotope emits alpha particles and gamma radiation, making it useful in certain medical applications, particularly in targeted alpha therapy for cancer treatment. However, due to its radioactivity, handling actinium-226 requires strict safety precautions to protect against radiation exposure.