R136a1 has a mass between 170 and 230 solar masses, according to an analysis of optical data from the speckle imager Zorro mounted on the 8.1-m Gemini South telescope, which is part of the International Gemini Observatory operated by NSF’s NOIRLab.
This image, taken with the Zorro imager on the 8.1-m Gemini South telescope, shows R136a1, the largest star yet discovered. Image credit: International Gemini Observatory / NOIRLab / NSF / AURA / T.A. Rector, University of Alaska Anchorage & NSF’s NOIRLab / M. Zamani, NSF’s NOIRLab / D. de Martin, NSF’s NOIRLab.
R136a1 is a member of R136, a massive, young star cluster about 170,000 light-years away.
Also known as RMC 136, the cluster is only a few light-years across and is only a few million years old.
It resides in the Tarantula Nebula, a turbulent star-birth region in the Large Magellanic Cloud, a satellite galaxy of our Milky Way Galaxy.
R136 hosts at least nine very massive stars — over 100 times more massive than the Sun — as well as dozens of stars exceeding 50 solar masses.
“The formation of very massive stars is an unsolved problem in astrophysics,” said Dr. Venu Kalari, an astronomer in the Departamento de Astronomia at the Universidad de Chile, Gemini Observatory and NSF’s NOIRLab, and colleagues.
“Most massive stars reside within the dense central cores of young massive star clusters, and have short lifetimes (less than 2-3 million years), making observations challenging.”
“Particularly challenging are resolving local templates of rich super-star clusters, with cluster masses more than 10,000 solar masses, that were common in the early Universe.”
“These are highly compact, relatively distant objects making extreme spatial resolution observations crucial to resolve individual very massive stars found at their centers.”
“The R136 cluster offers the best local template for starburst clusters found at higher redshifts, and is the most massive resolved star cluster known,” they said.
“It has a stellar mass of 10,000 solar masses within its central 0.2-parsec core, containing a total ~25 O-type stars within 100 arcsec.”
“The most massive star yet known, R136a1, is situated at it’s center.”
Previous observations suggested that R136a1 had a mass somewhere between 250 to 320 times the mass of the Sun.
The new Zorro/Gemini South observations indicate that this star may be only 170 to 230 solar masses.
“Our results show us that the most massive star we currently know is not as massive as we had previously thought,” Dr. Kalari said.
“This suggests that the upper limit on stellar masses may also be smaller than previously thought.”
The results also have implications for the origin of elements heavier than helium in the Universe.
These elements are created during the explosions of stars more than 150 times the mass of the Sun in events that astronomers refer to as pair-instability supernovae.
If R136a1 is less massive than previously thought, the same could be true of other massive stars and consequently pair instability supernovae may be rarer than expected.
“We began this work as an exploratory observation to see how well Zorro could observe this type of object,” Dr. Kalari said.
“While we urge caution when interpreting our results, our observations indicate that the most massive stars may not be as massive as once thought.”
The findings will be published in the Astrophysical Journal.
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Venu M. Kalari et al. 2022. Resolving the core of R136 in the optical. ApJ, in press; arXiv: 2207.13078
Source link: https://www.sci.news/astronomy/gemini-south-images-most-massive-known-star-11118.html
