Science
New Method for Finding Universe's First Stars Discovered
By Xavier Roxy
May 9, 2024
A recent study led by the research group of Professor Jane Lixin Dai, affiliated with the Department of Physics at the University of Hong Kong (HKU), has proposed a groundbreaking method for detecting first-generation stars, known as Population III (Pop III) stars. Despite their significant role in shaping our universe, these elusive celestial entities have never been directly detected.
The study's findings have received widespread acclaim from the international astronomy community and were recently highlighted by the Space Telescope Science Institute, which operates several NASA telescopes. This potential breakthrough could unlock secrets about our universe's origins and deepen our understanding of its evolution.
The results were published in The Astrophysical Journal Letters.
In the immediate aftermath of the Big Bang, Pop III stars began to form primarily from hydrogen and helium. These stellar pioneers differed greatly from contemporary stars like our own sun or even those currently forming; they were incredibly hot, massive, and short-lived.
Pop III stars played a vital role in factories synthesizing most elements heavier than hydrogen and helium around us today. They also served as important catalysts for later generations' star formation and galaxy development. However, direct detection efforts have proven fruitless due to their far-off locations in space-time, rendering them too faint for ground-based or space-based telescopes.
For the first time ever, HKU scientists propose a novel method for detecting these early-universe denizens: through tidal disruption events (TDE). As per this theory posited by Professor Dai's team at HKU’s Physics Department, if a Pop III star strays near a massive black hole, it can be torn apart by tidal forces, creating an extremely luminous flare as debris is consumed by said black hole.
Following a thorough investigation into this complex physical process, researchers demonstrated that these flares can shine across billions of light years, reaching observers on Earth today—uniquely identifiable signatures that confirm existence while shedding light on properties intrinsic to Pop III stars.
Professor Dai explained further, noting, "As these energetic photons travel vast distances, the flare's timescale is stretched due to universal expansion. The TDE flares rise and decay over a protracted period of time, distinguishing them from nearby solar-type star TDEs."
Dr. Rudrani Kar Chowdhury, Postdoctoral Fellow at HKU’s Physics Department and primary author of the paper, added, "Interestingly, not just the timescales but also their wavelengths are stretched; optical and ultraviolet light emitted by these TDEs transforms into infrared emissions upon reaching Earth.”
The excitement surrounding this discovery has been amplified by NASA's recently launched James Webb Space Telescope (JWST) and the upcoming Nancy Grace Roman Space Telescope (Roman). Both have the capability to observe such distant infrared emissions.
Professor Priya Natarajan from Yale University’s Astronomy and Physics Department stated that Roman's unique ability to simultaneously observe large sky areas while delving deep into the early universe makes it an ideal probe for detecting Pop III TDE flares, indirectly confirming the existence of Pop III stars.
Janet Chang, a Ph.D. student at HKU’s Physics Department, expects dozens of these events to be detected annually with proper observational strategies in place.
This promising research heralds substantial potential for identifying distinct sources within the next decade, leading to exciting revelations about Pop III stars and further unraveling mysteries surrounding our universe's birth.
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