The James Webb Space Telescope (JWST), a landmark of astronomy that launched in December of 2021, explores not only space but also time. Even light’s speed is finite; therefore, when the light of distant objects reaches eyes on Earth, the images will represent what the objects looked like at a certain point in the past. The farthest objects give us the oldest light, and therefore the oldest images of those objects. A year after the launch of the JWST, a group of astronomers claim that the telescope has captured light from the oldest generation of stars in the universe.

Astronomers classify groups of stars by age by sorting them into populations. Walter Baade developed the concept of stellar populations in the 1940s, measuring metal content in stars to determine which group they belonged to. Near the beginning of the universe, stars were composed entirely of primordial gases, such as hydrogen and helium. These gases originated directly from the Big Bang. Heavier elements, including metals, then formed in the cores of those stars, creating material that would then be recycled in future generations of stars. Astronomers originally created two populations of stars: Population I, metal-rich (younger) stars, and Population II, metal-poor (older) stars. However, population II stars, despite their shortage of metals, are not quite as metal-poor as the primordial gases; therefore, astronomers have created a third population for the oldest stars.

No astronomer has yet discovered a Population III star. Swinburne University’s Encyclopedia of Astronomy: “[…] it is extremely unlikely that we will ever observe a Pop III star and they will remain hypothetical entities.” This is likely because most Population III stars were extremely massive, and therefore burned their fuel rapidly. In all probability, no Population  III stars exist today. Therefore, one must look far back in time to capture one. Until the launch of the JWST, finding these stars was beyond the capabilities of astronomers’ technology.

The launch of the JWST has greatly expanded the possibilities for researchers. Now, researchers can look up to 13.5 billion years into the past, studying the earliest stars and galaxies. One group of researchers led by researcher Xin Wang has taken this opportunity to search for the fabled Population III stars. These stars, in theory, should emit frequencies of light that indicate the presence of helium II, or helium atoms that lack one of their electrons. The team of researchers, after scanning thousands of galaxies, found data for a distant galaxy that existed about 620 million years after the Big Bang. One half of the galaxy was found to have the helium II signature, suggesting the presence of Population III stars.

However, the paper has not yet been peer-reviewed, and some scientists have urged caution before declaring Population III stars no longer hypothetical. Daniel Whalen, an astrophysicist at the University of Portsmouth, commented that the “[the data]’s not clean evidence.” To them, it seems that the signatures could come from other objects, like the accretion disks of black holes.

Multiple teams are now searching for Population III stars using other techniques and the JWST’s data. Some even hope to find definitive evidence in the next weeks or months, detecting stars in extremely bright galaxies that the telescope has found. The hypothesis regarding Population III stars, the first stars in the universe, may soon be confirmed.

References: 

1. Koh, Daegene. “Population III stars: The Universe’s ultimate reclusive pop stars | Kavli Institute for Particle Astrophysics and Cosmology (KIPAC).” Kavli Institute for Particle Astrophysics and Cosmology (KIPAC), 8 March 2018, https://kipac.stanford.edu/highlights/population-iii-stars-universes-ultimate-reclusive-pop-stars. Accessed 13 February 2023.
2. NASA. “Early Universe – Webb/NASA.” James Webb Space Telescope, https://webb.nasa.gov/content/science/firstLight.html. Accessed 13 February 2023.
3. NASA. “Science Themes – Webb/NASA.” James Webb Space Telescope, https://webb.nasa.gov/content/science/index.html. Accessed 13 February 2023.
4. O’Callaghan, Jonathan. “Astronomers Say They Have Spotted the Universe’s First Stars.” Quanta Magazine, 30 January 2023, https://www.quantamagazine.org/astronomers-say-they-have-spotted-the-universes-first-stars-20230130/. Accessed 13 February 2023.
5. Swinburne University. “Population III | COSMOS.” Centre for Astrophysics and Supercomputing, https://astronomy.swin.edu.au/cosmos/p/Population+III. Accessed 13 February 2023.
6. Wang, Xin, et al. “[2212.04476] A strong He II $λ$1640 emitter with extremely blue UV spectral slope at $z=8.16$: presence of Pop III stars?” arXiv, 8 December 2022, https://arxiv.org/abs/2212.04476. Accessed 13 February 2023.