They illuminated the nascent universe with the light of millions of suns, and for the first time astronomers detected the chemical trace of massive stars, “celestial monsters” in a galaxy that appeared more than ten billion years ago.
“We believe we have found the first evidence for the existence of these unusual stars,” Corine Charbonnell, a professor of astronomy at the University of Geneva, said in a statement. Preference for describing unusual stars is not stolen, so far only in theory.
The largest star observed so far has the equivalent mass of just over 300 suns. One is described in the study published in the May edition ofAstronomy and astrophysics It leaves it far away, with an estimated mass between 5,000 and 10,000 times that of the Sun.
The astrophysicist-led team — together with scientists from the Universities of Geneva and Barcelona and the Astrophysical Institute in Paris — theorized their existence in 2018 to explain an astronomy puzzle: the great diversity of star formation in globular clusters.
Generally very old, these clusters concentrate many millions of stars into a small volume. Advances in astronomy reveal an increasing number of them, like a kind of “missing link” between the first stars and the first galaxies. Our Milky Way galaxy, which contains more than a hundred billion stars, has about 180 globular clusters, and this is what the press release issued by the University of Geneva reminds us.
The mystery lies in the fact that many of the stars in these clusters contain elements that require enormous temperatures to produce them, up to 70 million degrees for aluminum. Temperatures much higher than those that stars reach in their cores, a maximum of 15 to 20 million degrees – like our Sun.
The proposed solution is “contamination” by a massive star, the only one capable of reaching this extreme temperature. Scientists imagine that such massive stars are born from successive collisions in the very dense and narrow space of the cluster.
“star seed”
“A kind of star seed will swallow more and more stars,” Ms. Charbonnel explains to AFP. And it becomes “like a huge nuclear reactor, constantly feeding matter, which will spew out a lot” in the mass. This material will nourish young stars in the formation stage, proportional to their “closeness to the massive star”.
It remained to find evidence of this phenomenon. The team discovered it in a galaxy from the early ages of the universe, GN-Z11.
Discovered in 2015 by a colleague of Corinne Charbonnel, this galaxy is among the most distant galaxies observed, more than 13 billion light-years away, and thus one of the oldest, already existing 440 million years after the Big Bang.
Discovered by the Hubble Space Telescope and its successor James Webb, this tiny red spot has given two key clues: a very high density of stars and above all a lot of nitrogen. An element whose existence in such proportions can only be explained by the combustion of hydrogen at extreme temperatures. A phenomenon that can only occur in a massive star.
If the team sticks to its theory, “Like some kind of imprint of our supermassive star, it’s as if we’ve found a bone,” Ms. Charbonnel continues: “And we’re speculating on the head of the monster behind it all…”
The hope of celebrating one day is insignificant. Scientists estimate the life expectancy of a supermassive star to be about two million years, in the blink of an eye on cosmic timescales.
But they suspect it may have appeared in globular clusters 2 billion years ago. Thus leaving a mark to get to know her better.
