'Monster Stars' Lit Up the Early Universe

Scientists have discovered that "monster stars" lit up the early Universe, shining as bright as 100 million Suns, according to a new study.

The first stars in the Universe were born several hundred million years after the Big Bang, ending a period known as the cosmological "dark ages" - when atoms of hydrogen and helium had formed, but nothing shone in visible light. Now, two Canadian researchers have calculated what these objects were like, and suffice to say they were bright.

They published their results in a paper in Monthly Notices of the Royal Astronomical Society.

Stars are born out of clouds of dust and gas. When the cloud collapses, a dense, hot core forms and begins gathering new dust and gas, eventually becoming a star, NASA explains.

To better understand this process in the very first stars of the Universe, scientists Alexander DeSouza and Shantanu Basu used a model to show how the luminosity of the stars would have changed as they formed from the aforementioned gravitational collapse. It turns out this early evolution was quite chaotic, with clumps of material forming and spiraling into the center of the cloud, creating bursts of luminosity a hundred times brighter than average.

These first stars would have been at their brightest when they were "protostars," still forming and pulling in material.

They could even cluster together in phenomenally bright groups of 10 to 20 protostars, with periods when they were as luminous as 100 million Suns.

Light from these monster stars has travelled towards us for almost 13 billion years. So from Earth, though they boast an incredible brightness, they appear faint and also have their light stretched out into infrared wavelengths by the expansion of the Universe. This makes it difficult for scientists to observe these early stars, but the next generation James Webb Space Telescope (JWST) will nonetheless survey the skies to look for them. Although the luminosity of an individual first star is probably too faint for JWST to spot it, the new work suggests that clusters of the first protostars could be prominent beacons in the early Universe.

"Seeing the very first stars is a key science goal for JWST and part of astronomers' quest to track the history of the cosmos," Basu said in a statement. "If we're right, then in just a few years' time, we could see these enigmatic and dazzlingly bright objects as they came into being, and lit up the Universe around them."

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