The James Webb Space Telescope has helped astronomers detect the first chemical signs of massive stars, the “celestial beasts” that blaze in the brightness of millions of suns in the early universe.
To date, the largest stars observed anywhere have a mass of about 300 times that of our sun.
But the massive star described in a new study is estimated to have a mass of 5,000 to 10,000 suns.
The team of European researchers behind the study previously theorized about the existence of massive stars in 2018 in an effort to explain one of astronomy’s biggest mysteries.
For decades, astronomers have been baffled by the huge variety in the composition of the different stars packed into so-called globular clusters.
Clusters, which are often very old, can contain millions of stars in a relatively small space.
Advancements in astronomy have revealed an increasing number of globular clusters, which are thought to be the missing link between the universe’s first stars and the first galaxies.
Our galaxy, the Milky Way, which includes more than 100 billion stars, includes about 180 globular clusters.
But the question remains: Why do the stars in these clusters contain such a variety of chemical elements, even though they are all supposed to have been born around the same time, from the same gas cloud?
The raging “star seed”.
Many stars contain elements that require huge amounts of heat to produce, such as aluminum which needs to heat up to 70 million degrees Celsius.
This is much higher than the temperature that stars are thought to reach in their cores, around 15-20 million degrees Celsius which is similar to that of the Sun.
So the researchers came up with a possible solution: a raging, massive star that releases chemical “pollution”.
They hypothesized that these massive stars were born from successive collisions in tightly packed globular clusters.
“Some kind of star seed will swallow more and more stars,” Corine Charbonnel, an astrophysicist at the University of Geneva and lead author of the study, told AFP.
Eventually, she added, it will become “like a huge nuclear reactor that is constantly feeding on matter that will make a lot of it come out.”
She added that this discarded “pollution” would in turn nourish young forming stars, giving them a greater diversity of chemicals the closer they got to the massive star.
But the team still needs observations to support their theory.
Like finding a bone
They found them in the galaxy GN-z11, which is over 13 billion light years Far away – the light we see from it comes only 440 million years after the Big Bang.
It was discovered by the Hubble Space Telescope in 2015, and until recently held the record for the oldest observed galaxy.
That made it an obvious early target for Hubble’s successor as the space telescope’s most powerful, James Webb, which began making its first observations last year.
Webb provided two new clues: the amazing density of stars in globular clusters and, more importantly, the presence of a lot of nitrogen.
He really takes extreme heat to manufacture nitrogen, which researchers believe can only be produced by a massive star.
“Thanks to the data collected by the James Webb Space Telescope, we believe we have found the first evidence of the existence of these unusual stars,” Charbonnel said in a statement, also called Celestial Beasts.
If previously the team’s theory was “a kind of imprint of our supermassive star,” Charbonnel said, “this is a bit like finding a bone.”
“We’re speculating about the monster’s head behind all of this,” she added.
But there is little hope of observing this beast first hand.
Scientists estimate that the life expectancy of massive stars is only about 2 million years – a blink of an eye in the cosmic time scale.
However, they doubt it spherical clusters They existed until about 2 billion years ago, and can reveal more traces of the massive stars they may once have hosted.
The study has been published in the journal Astronomy and astrophysics This month.
C. Charbonnel et al., N-Improvement in GN-z11: First Evidence for Nuclear Composition of Massive Stars in Proto-Global Cluster-like Conditions at High Redshift?, Astronomy and astrophysics (2023). DOI: 10.1051/0004-6361/202346410
© 2023 AFP
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