SC Connecticut News

Astronomers from Yale and the University of Hong Kong have put forth a new strategy to detect the universe's first stars, known as "Population III" stars. These stars, which lit up the universe just a few hundred million years after the Big Bang, have not yet been observationally detected. The researchers suggest that these stars can be found by looking for their final flares.

"Population III" stars were initially metal-free, composed primarily of hydrogen and helium. Over time, they began to produce metals in their core, serving as a bridge to the formation of later generations of stars. These early stars are believed to be more massive and hotter than Earth's sun and other younger stars, with shorter lifespans.

"The recent detection of the first black holes by the James Webb Space Telescope suggests that they are also in place around the same time as the first stars," said Priyamvada Natarajan, Professor and Chair of Astronomy at Yale's Faculty of Arts and Sciences (FAS), and co-author of a new study published in The Astrophysical Journal Letters. "We realized that the fireworks created by the ripping apart of a Population III star that strays too close to a black hole should be detectable."

The study proposes that if a "Population III" star encounters a black hole, it would result in a "tidal disruption event" (TDE), where the black hole tears apart the star, creating an exceptionally bright flare. This flare would be bright enough and long-lived enough to reach Earth today across billions of light years. Moreover, this flare would carry an identifiable "signature" discernable to astronomers.

"These TDE flares will rise and decay over a very long period of time, which sets them apart from the TDEs of solar type stars in the nearby universe," said Jane Dai, astronomer at the University of Hong Kong and principal investigator of the research team.

The study's first author, Rudrani Kar Chowdhury from the University of Hong Kong, added that the wavelength of the flares' light is also stretched. "The optical and ultraviolet light emitted by the TDE will be transferred to infrared wavelengths when reaching the Earth," she said.

According to the researchers, this infrared light can be detected. They believe that two flagship NASA missions, the James Webb Space Telescope and the upcoming Nancy Grace Roman Space Telescope, have the capability to detect such infrared emissions even from great distances.

"Roman’s unique capabilities of simultaneously being able to observe a large area of the sky and peek deep into the early universe makes it a promising probe for detecting these Pop III TDE flares," Natarajan said. "This may be the only way in which we can infer the presence of Pop III stars."

The researchers anticipate such discoveries could occur within the next decade.