The James Webb telescope has discovered traces of stars 10,000 times more massive than the sun!

The majority of stars in the Milky Way are not more massive or lighter than the Sun and they live for at least a few billion years. Stars of a few tens of solar masses are much rarer. We know of some cases where they appear to be just over 200 solar masses, but stellar composition theory tells us that stars above 150 solar masses become very unstable.

However, early in the history of the visible universe, when the nuclear synthesis of elements heavier than lithium was just beginning in the first stars a few hundred million years after the Big Bang, the presence of massive stars exceeding a thousand solar masses existed. They are made possible precisely because those elements that astrophysicists by convention call metals—even if carbon, oxygen, and nitrogen are not metals to alchemists—modify the way light produced by fusion of thermonuclear reactions interacts with stellar matter, shifting the equilibrium between the gravitational forces that compress a star and the radiation pressure that counteracts gravitational contraction.

Nicolas Prantzos, CNRS, Astrophysical Institute in Paris, tells us about the nuclear structure of the elements in two videos. © French Society of External Biology

Massive stars produced by multiple mergers?

Astrophysicists have considered the presence of massive stars in the context of several scenarios and in particular to explain strange anomalies observed in the chemical composition of stars in globular clusters. Now, precisely, an international team made up of researchers from the Universities of Geneva (Unige) and Barcelona, ​​as well as from the Astrophysical Institute in Paris (CNRS and Sorbonne) has just announced via Article published in Astronomy and astrophysicsAnd But they can be found for free at arXiv, which thought it had found the chemical trace of these stars. These traces support the existence of stars with 5,000 to 10,000 solar masses in globular proton clusters, born about 440 million years after the Big Bang.

To get this result, the researchers packed the James Webb telescope by observing a compact galaxy the farthest ever detected by the Hubble telescope: GN-z11.

To understand what’s going on with the work published now, remember that globular clusters are groups of stars that are among the oldest known. They are not recent products of stellar nurseries like the open clusters observed in the spiral arms of the Milky Way, for example. But just like open clusters, the stars that make up globular clusters must have been born at or around the same time, more than 10 billion years ago.

So globular clusters should be fairly chemically homogeneous and with metallic levels, low metallicity, as the astrophysicists put it in their terminology. However, in these globular clusters we sometimes find significant deviations from these predictions.

The theory proposed to explain these anomalies is based on the fact that globular clusters are particularly compact, and one can find up to a million stars in a sphere a hundred light-years across at most. Calculations then show that some sort of chain reaction can take place, eventually causing a large number of stars to collide and end up, through a sort of snowball effect, massive stars which can therefore have between 5,000 and 10,000 masses. Umbrella.

AstrobioEducation video course. © French Society of External Biology

Strange and massive structure of the nitrogen nucleus

We know how to model these stars and the thermonuclear reactions that make them shine for at most two million years before they explode in a supernova, sending newly formed elements back into the interstellar medium.

Calculations then show that these stars, whose cores are five times hotter than our sun (75 million degrees Celsius), will produce very specific amounts of heavy elements and especially many nitrogen nuclei. So some of these stars born in clusters can somehow “contaminate” other stars after they explode, presenting anomalies in the abundance of oxygen, nitrogen, sodium or even aluminum that actually differ from one star to another in clusters.

However, as indicated in a press release from Unige Corinne CharbonnellEmeritus Professor in the Department of Astronomy in the University’s College of Science, and first author of the study with her colleague Nicholas Brentzos from the IPA,” Today, thanks to data collected by the James Webb Space Telescope, we believe we have found the first evidence of the existence of these unusual stars “.

Now let’s go back to the James Webb Telescope observations of the infrared galaxy GN-z11 observed as it was 13.3 billion years ago. Its core is particularly compact and everything indicates that it is surrounded by globular clusters. The researchers believe they have already been exposed to the “pollution” of the massive stars they began modeling in 2018.

In fact, it’s still in Unige’s press release,” It has been proven that this galaxy contains very high proportions of nitrogen and a very high density of stars This was stated by Daniel Scherer, co-author of the study and assistant professor in the Department of Astronomy, Faculty of Science, Unige University. ” In fact, the strong presence of nitrogen can only be explained by the combustion of hydrogen at extremely high temperatures, which only the cores of massive stars can reach, as shown by the models of Laura Ramirez-Galeano, a master’s student on our team. Corinne Charbonnell adds.