6 days ago
Are These 'Little Red Dots' The Universe's First Stars And Not Galaxies?
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JWST spotted over 300 mysterious red dots from the early universe. Though once thought to be galaxies, scientists now believe they may be massive stars, not galaxies
The James Webb Space Telescope (JWST) has realised humanity's ambition of observing the early universe. It recently transmitted images from when the universe was merely 600 million years old. However, these images revealed something puzzling: hundreds of small red spheres, now referred to as Little Red Dots (LRDs).
JWST identified over 300 of these red dots. Despite being faint and extremely distant, they appear unusually bright, suggesting a very high mass. Initially, scientists believed these were early galaxies, but new research proposes a surprising alternative: they may actually be supermassive stars (SMS), not galaxies.
A recent study by Devesh Nandal of the University of Virginia and Abraham Loeb of Harvard suggests these mysterious LRDs could be Population III supermassive stars; stars that formed in the very early universe. These stars contained no metals and could have masses up to 1 million times that of our Sun. However, they lived for only a few thousand years before exploding as supernovae.
These explosions may have contributed to the formation of the first supermassive black holes (SMBHs), which are now found at the centres of quasars and large galaxies.
The red appearance of LRDs is due to the thick clouds of gas and dust surrounding them. Initially, scientists speculated they might be active galactic nuclei (AGN), with black holes at their centres. However, key differences such as the absence of X-ray emissions, a flat infrared spectrum, and minimal light variation challenged that theory, prompting researchers to consider alternative explanations.
What Did the Research Find?
Nandal and Loeb created a model of a metal-free supermassive star with a mass of one million Suns. They found that its light spectrum and brightness closely matched those of the LRDs observed by JWST.
Most importantly, the model showed a strong Hβ emission line and Balmer absorption lines, features typically created when gas expands on the surface of a supermassive star. This strongly supports the theory that LRDs are not galaxies but giant stars.
Could This Solve a Cosmic Mystery?
If proven true, this theory could help solve a long-standing puzzle: how did SMBHs form so soon after the Big Bang? According to current models, they should have taken billions of years to develop. However, the presence of quasars and SMBHs just a few hundred million years after the Big Bang contradicts this.
The theory of short-lived, massive stars collapsing into black holes provides a much simpler explanation. The researchers adhered to the principle of Occam's Razor, the idea that the simplest explanation is often the most likely. While the AGN theory requires multiple complex assumptions, the SMS model explains all the observed features straightforwardly.
Nevertheless, scientists emphasise that this is still a developing theory. Further telescopic observations and improved modelling will be necessary to confirm whether these Little Red Dots are indeed ancient supermassive stars. Despite the limitations of current technology, JWST has opened a new window into the universe's earliest moments – and potentially, into one of its greatest mysteries.
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