James Webb Space Telescope Discovers Possible First Stars in the Universe

Astronomers have made a groundbreaking discovery with the James Webb Space Telescope (JWST), suggesting that it may have identified the first generation of stars, known as Population III (POP III) stars, formed shortly after the Big Bang. This significant finding revolves around a galaxy named LAP1-B, which the telescope has been studying. The light from LAP1-B has traveled for approximately 13 billion years to reach Earth, allowing scientists to observe the galaxy as it existed just 800 million years after the Big Bang.

The lead scientist on this research, Eli Visbal from the University of Toledo, expressed excitement about the implications of this discovery. “If indeed the stars of LAP1-B are Pop III, this is the first detection of these primordial stars,” he stated in an interview with Space.com. The research team relied on the exceptional sensitivity of the JWST, along with the effects of gravitational lensing, which enhanced the visibility of this distant galaxy.

Understanding Gravitational Lensing and Its Role

The phenomenon of gravitational lensing, predicted by Albert Einstein in his 1915 theory of general relativity, occurs when a massive body, such as a galaxy cluster, warps the space around it, magnifying the light from objects behind it. In this case, the galaxy cluster MACS J0416.1-2403, located about 4.3 billion light-years from Earth, acted as the gravitational lens that allowed astronomers to observe LAP1-B.

This observation is critical as it coincides with a pivotal era in the universe’s history known as “the epoch of reionization.” During this time, ultraviolet light emitted by the first stars and galaxies is believed to have transformed neutral hydrogen and helium gas into a hot, charged state known as plasma, marking the end of the “cosmic dark ages.”

According to Visbal, the formation of POP III stars occurred around 200 million years after the Big Bang, during a period when the universe had cooled enough for electrons and protons to combine and create the first atoms of hydrogen. “In the standard model of cosmology, POP III stars form in very small dark matter structures that serve as building blocks for larger galaxies,” he explained.

Significance of Population III Stars

Identifying POP III stars is essential for understanding the early stages of galaxy formation and evolution. These stars are characterized by their low metallicity, meaning they contain minimal heavy elements compared to modern stars, like our sun, which is classified as a POP I star. This low metallicity contributes to the massive size of POP III stars, which can be more than 100 times the mass of the sun.

“The simulations indicate that primordial gas cools less efficiently than gas rich in heavy elements, leading to less fragmentation during star formation,” Visbal noted. This results in POP III stars being formed in relatively small groups, typically around 1,000 solar masses. The research team found that the stars in LAP1-B are surrounded by gas with limited metal content, reinforcing their hypothesis about the nature of these ancient stars.

The implications of this discovery extend to the search for more POP III stars in the early universe. Visbal noted that the use of gravitational lensing could be a promising method for locating additional examples of these elusive stars at high redshifts. “I was pleasantly surprised to find that our calculation showed that they should be common enough to observe behind a cluster like MACS J0416,” he remarked.

The team’s findings were published in The Astrophysical Journal Letters in late October 2023. Moving forward, they plan to conduct more detailed hydrodynamical simulations to explore the transition from POP III to POP II stars, potentially providing further insights into the composition and evolution of the universe’s earliest stellar populations.