(ORDO NEWS) — Taking full advantage of the 8.1-meter Gemini South telescope in Chile, astronomers have obtained the clearest image of the star R136a1, the most massive known star in the universe.
The study, led by NOIRLab’s Venu M. Kalari, questions our understanding of the most massive stars and suggests they may not be as massive as previously thought.
Astronomers have yet to fully understand how the most massive stars, those with more than 100 times the mass of the sun, are formed.
Observations of these giants are especially difficult to solve this puzzle, they usually live in the densely populated cores of star clusters, shrouded in dust.
Giant stars also live fast and die young, burning up in just a few million years. By comparison, our sun has passed less than half of its projected 10 billion years of life.
The combination of dense stellar arrangements, relatively short lives, and vast astronomical distances makes it difficult to distinguish between individual massive stars in clusters.
Using the capabilities of Gemini South’s Zorro instrument, astronomers have obtained the sharpest image of R136a1, the most massive star known.
Previous observations have established that R136a1 has a mass between 250 and 320 times that of the Sun. However, new observations by Zorro show that this giant star could be only 170 to 230 times as massive as the Sun. But even at this rate below R136a1 is still considered the most massive known star.
Astronomers can estimate the mass of a star by comparing its observed brightness and temperature with theoretical predictions.
The sharper image of Zorro allowed scientists to look more closely at R136a1’s brightness apart from nearby stars, leading to a lower estimate of its brightness, and hence its mass.
“Our results show that the most massive star currently known to mankind is not as massive as previously thought.
This suggests that the upper limit of stellar masses may also turn out to be less than previously thought, ”explains V. Kalari.
This result also has implications for the origin of elements heavier than helium in the universe. These elements are formed by the explosion during the death of stars, the mass of which is more than 150 times the mass of the Sun, an event called pair-unstable supernovae.
If R136a1 is less massive than previously thought, then a similar conclusion could be drawn for other massive stars, hence pair-unstable supernovae may be rarer than expected.
With many thousands of short-exposure shots of a bright subject and careful processing of the data, almost all motion blur can be eliminated.
“This discovery is yet another example of the scientific advances we can achieve by bringing together international collaboration, world-class infrastructure and a brilliant team,” said NSF Gemini Program Officer Martin Still.
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