"Cosmic abundances" refer to the relative amounts of different elements and isotopes found in the universe. These abundances are primarily determined by processes such as nucleosynthesis in stars and during the Big Bang. For example, hydrogen and helium are the most abundant elements, making up about 98% of the observable universe. Scientists study cosmic abundances to understand the formation and evolution of galaxies, stars, and planets. By analyzing light from distant celestial objects, researchers can determine the composition of these objects and gain insights into the history of the universe and the processes that shaped it.