A startling study, which looked at data 10 times more comprehensive compared to previous similar efforts, found that half of all the stars that have ever existed were created between 9 and 11 billion years ago, with the other half created in the years since. What this means is an exponential fall in new stars being born, to the point that no more than 5 percent more stars will form over the remaining history of the cosmos, even if we wait forever.
For years, scientists were confused by the disparity between the number of stars we can observe and the number of stars we know should have been created by the universe. Numerous studies have each looked at specific periods in our Universe’s history in order to assess star formation, however since multiple methods were used, it was fairly difficult to aggregate and establish a comparative conclusion.
A team of international researchers decided to run a complete survey from the very dawn of the first stars using three telescopes — the UK Infrared Telescope and the Subaru Telescope, both in Hawaii, and Chile’s Very Large Telescope. Snapshots were taken of the look of the Universe at various instances in time when it was 2, 4, 6 and 9 billion years old – that’s 10 times as large as any previous similar study. The astronomers concluded that the rate of formation of new stars in the Universe is now only 1/30th of its peak.
“You might say that the universe has been suffering from a long, serious ‘crisis:’ cosmic GDP output is now only 3 percent of what it used to be at the peak in star production!” said David Sobral of the University of Leiden in the Netherlands.
“If the measured decline continues, then no more than 5 percent more stars will form over the remaining history of the cosmos, even if we wait forever. The research suggests that we live in a universe dominated by old stars.”
According to the current accepted models of the Universe’s evolution, stars first began to form some 13.4 billion years ago, or 300 million years after the Big Bang. Now, these ancient stars were nothing like those commonly found through out the cosmos. These were like titans with respect to Olympus’ gods – standing at hundreds of times more massive than our sun. Alas, the giants’ life would’ve been short lived, quickly exhausting their fuel, they had only one million years or so worth of time. Lighter stars, like our own, in contrast can shine long and bright for billions of years.
It’s from these huge, first stars that other smaller, more long-lived stars form as the cosmic dust was recycled. Our Sun, for example, is thought to be a third generation star, and has a typical mass, or weight, by today’s standards. To identify star formations, the astronomers searched for alpha particles emitted by Hydrogen atoms, appearing as a bright red light.
“Half of these were born in the ‘boom’ that took place between 11 and 9 billion years ago and it took more than five times as long to produce the rest,” Sobral said. “The future may seem rather dark, but we’re actually quite lucky to be living in a healthy, star-forming galaxy which is going to be a strong contributor to the new stars that will form.
“Moreover, while these measurements provide a sharp picture of the decline of star-formation in the Universe, they also provide ideal samples to unveil an even more fundamental mystery which is yet to be solved: why?”
Results were published in the Monthly Notices of the Royal Astronomical Society.
