The James Webb Space Telescope has helped astronomers detect the first chemical signatures of „sky monsters” burning with the brightness of millions of suns in the early universe.
So far, the largest stars observed anywhere are 300 times the mass of our Sun.
But a new study estimates the mass of the supermassive star described at between 5,000 and 10,000 suns.
The team of European researchers behind the study theorized the existence of massive stars in 2018 in an attempt to explain one of astronomy’s biggest mysteries.
For decades, astronomers have been puzzled by the enormous diversity in the composition of different stars in so-called globular clusters.
Clusters, often very old, can contain millions of stars in a relatively small space.
Advances in astronomy have revealed an increasing number of globular clusters, considered the missing link between the universe’s first stars and first galaxies.
With more than 100 billion stars, our Milky Way galaxy consists of about 180 globular clusters.
But the question remains: Why do the stars in these clusters have so many different chemical elements, presumably all born at the same time, from the same gas cloud?
’Seed Star’ Rampages
Many stars contain elements that require enormous amounts of heat to produce, such as aluminum, which requires temperatures of up to 70 million degrees Celsius.
Around the 15-20 million Celsius mark, similar to the Sun, this is much higher than the temperature at which stars are thought to rise at their cores.
So the researchers came up with a possible solution: a massive star that spews out chemical „pollution.”
They hypothesize that these massive stars are born from successive collisions in tightly packed globular clusters.
Corinne Charbonnel, an astrophysicist at the University of Geneva and the lead author of the study, told AFP that „a kind of seed star will engulf more and more stars.”
It will eventually „become like a big nuclear reactor, constantly feeding material and spewing out a lot,” he added.
This discarded „pollution” will feed the young forming stars, giving off a variety of chemicals as they get closer to the supermassive star, he added.
But the team needed more observations to support their theory.
’Like finding a bone’
They found them in the galaxy GN-z11, 13 billion light-years away—the light we see from it comes 440 million years after the Big Bang.
It was discovered by the Hubble Space Telescope in 2015, and recently held the record for being the oldest observed galaxy.
It’s Hubble’s successor, the most powerful space telescope, the James Webb, which began releasing its first observations last year.
Webb provided two new clues: the incredible density of stars in globular clusters and—more importantly—the presence of a lot of nitrogen.
It takes truly extreme temperatures to create nitrogen, which researchers believe can only be produced by a supermassive star.
„Thanks to data collected by the James Webb Space Telescope, we believe we have discovered the first clue to the existence of these unusual stars,” Charbonnel said in a statement, which also called the stars „celestial monsters.”
Charbonnel said the team’s theory previously suggested that „if this is a kind of footprint of our supermassive star, it’s like finding a bone.”
„We speculate about the head of the beast behind all this,” he added.
But there is no hope of ever directly observing this beast.
Scientists estimate that the lifespan of massive stars is only about two million years—a blink of an eye on the cosmic time scale.
However, they suspect that globular clusters existed until about two billion years ago, and can still reveal traces of the supermassive stars they once hosted.
The study is published in the journal Astronomy and Astrophysics This month.
More information:
C. Charbonnel et al, N-enhancement in GN-z11: first evidence for nucleosynthesis of supermassive stars in proto-globular cluster-like states at high redshift?, Astronomy & Astrophysics (2023) DOI: 10.1051/0004-6361/202346410