While the history of spectroscopy is long and complex, with contributions from many individuals, Isaac Newton is often credited with being the first to systematically study the phenomenon of light decomposition through a prism.

Here's why:

* 1666: Newton conducted his famous experiment with a prism, observing that white sunlight could be separated into a spectrum of colors. This laid the groundwork for understanding the spectral properties of light.

* Newton's work was the first to demonstrate the fundamental nature of light and its interaction with matter.

However, it was Joseph von Fraunhofer in the early 19th century who took this work further by mapping the specific dark lines (Fraunhofer lines) in the solar spectrum, which later proved to be instrumental in understanding the chemical composition of the sun and stars.

Therefore, while Newton started the journey, it was Fraunhofer who truly established the field of spectroscopy as we know it today.

Later, Gustav Kirchhoff and Robert Bunsen further developed spectroscopy as a tool for chemical analysis, leading to its widespread use in chemistry, physics, and astronomy.