New image of the most massive known star

The largest star ever discovered just revealed a surprising new insight: ScienceAlert

How big can a star grow? As it turns out, it’s not as big as we thought.

The sharpest image ever taken of the largest known star shows upper limit the mass of a sun Possibly much smaller than previous estimates.

Star R136a1 was initially measured to be about 250 to 320 times the mass of our sun. New estimates put it at between 150 and 230 times the mass of the sun.

This new figure of just under 200 solar masses still makes the star a heavyweight record holder, but a downward revision in its mass could have deeper implications.

This work is part of a project to understand the cluster it is in, called R136. It’s located in the Tarantula Nebula, a hotbed for star formation in a satellite galaxy of the Milky Way called the Large Magellanic Cloud.

This cluster happens to contain some of the most massive stars known; the masses have now also been revised downwards. Since these masses are key anchors for a function of the upper limit of mass for massive stars, this work could mean that our previous upper limit of stellar mass was wrong.

“Our results suggest that the most massive stars we currently know are not as massive as we previously thought,” said Venu Karari, an astronomer and astrophysicist at the Gemini Observatory. “This suggests an upper bound on stellar mass. It may also be smaller than previously thought.”

While we don’t know what the upper limit to a star’s mass is, calculations and modeling suggest that there really must be one. It is widely believed that at a point called Eddington, the outward pressure of the core radiation exceeds the inward gravitational pressure, forcing the outer layers of the star to be ejected.

Previous research identified 150 solar masses as the Eddington limit. Then new data was obtained on R136 stars, a whole bunch of which were significantly more massive.

In addition to challenging the Eddington limit, these stars — young, very hot and very large — also challenge models of star formation. Later research found that such chokes could be formed by stellar mergers, but we still don’t have a good answer to the Eddington limit question.

New image for R136a1.

Determining an upper mass limit based on an accurate reference point will go a long way towards solving this thorny puzzle. Stellar mass can be calculated by obtaining precise observations that reveal the star’s brightness and temperature. So Kalari and his colleagues set out to acquire new, sharper images of star clusters, especially R136a1.

This gave the team the tools to design a new 196 solar masses (plus or minus a few tens of solar masses) for R136a1, and 151 and 155 solar masses for the other two large stars in the cluster, R136a2 and R136a3 — Below 195 are -211 and 180-181 respectively.

This has implications for the production of heavy elements in the universe. You probably know that massive stars eventually turn into black holes. They eject their outer material and form a black hole from the collapsed stellar core. However, there is an upper limit: beyond about 130 solar masses, the star can explode in a so-called double unstable supernova, in which case the entire star, core and everything explodes.

In these incredibly violent events, subatomic processes lead to the production of heavy elements. If there are fewer stars in this mass range, then we need to reconsider the potential contribution of unstable supernovae to the heavy elements we observe in space.

“The importance of the existence of unstable supernovae cannot be overemphasized, because a pair of unstable supernovae from a 300-solar-mass star would produce and release more in the interstellar medium than the entire stellar mass function below it. many metals, which will revolutionize our understanding of galactic chemical evolution models,” the researchers wrote in their paper.

However, the result was achieved by pushing the limits of the Zorro instrument on the Gemini South Telescope, and the researchers urged caution in interpreting the findings.

The next step will be to try to verify the conclusions, perhaps by acquiring and comparing observations from another instrument.

The study has been accepted for publication in astrophysical journaland is available on arXiv.

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