Yes, the earliest stars in the universe, including the population III stars, are believed to have emitted a different light spectrum compared to what we observe from stars today. Population III stars were the first generation of stars that formed after the Big Bang, and they were composed almost entirely of hydrogen and helium, with very little to no heavier elements.
The absence of heavy elements in these stars had significant implications for their formation and evolution, as well as their spectral characteristics. The light emitted by population III stars would have had a different spectrum compared to later-generation stars that contain heavier elements.
The lack of heavy elements affects the opacity and energy transport mechanisms within these stars. The primordial composition of population III stars led to different physical processes and conditions in their interiors, resulting in unique spectral features.
For example, population III stars were much more massive than most stars in the present-day universe. Their high mass and luminosity caused them to burn through their nuclear fuel relatively quickly, leading to short lifetimes. These stars likely had very high surface temperatures and emitted intense ultraviolet radiation. Their spectra would have been rich in ultraviolet light, and they may have emitted less visible and infrared light compared to present-day stars.
Additionally, the absence of heavy elements would have affected the opacity of the stellar atmosphere, potentially leading to different absorption and emission features in their spectra.
Although population III stars themselves are not directly observable today, their effects on the surrounding environment and the early universe can be studied indirectly through various methods, such as the detection of their remnants or the impact they had on the reionization of the intergalactic medium.
Understanding the spectral characteristics of population III stars is an active area of research, and ongoing observational and theoretical efforts aim to shed more light on the nature and properties of these early stars.