Sharpest image taken of universe’s most massive known star

Findings suggest upper limit on masses of stars may be smaller than earlier thought

Astronomers have obtained the sharpest image ever of the most massive known star in the universe, an advance that suggests giant stars may not be as huge as previously thought.

Scientists trying to understand how some of the biggest known stars – some over 100 times the mass of the Sun – are formed have found it particularly challenging to obtain observations of these giants.

This is because they often dwell in the densely populated hearts of dust-shrouded star clusters.

Such stars also live fast and die young, burning through their energy reserves in only a few million years, researchers say.

Using the 8.1m Gemini South telescope in Chile, which is part of the International Gemini Observatory operated by the US National Science Foundation’s NOIRLab, astronomers could obtain the sharpest-ever image of R136a1 — the most massive known star.

While past studies suggested that R136a1 had a mass between 250-320 times that of the Sun, the new observations indicate this giant star may be only 170-230 times the solar mass.

Although it still qualifies as the most massive known star, the findings according to the astronomers, suggest that “the upper limit on stellar masses may also be smaller than previously thought”.

The study results also have implications for the origin of elements heavier than helium in the universe that are created during the cataclysmic explosive death of stars over 150 times the mass of the Sun.

Earlier telescopic observations of the massive star could not obtain images sharp enough to pick out all the individual stellar members of the nearby cluster.

In the new study, however, the Gemini South’s Zorro instrument could surpass the resolution of previous observations by using a technique known as “speckle imaging” that enabled ground-based telescopes to overcome the blurring effect of Earth’s atmosphere.

Using this technique of taking thousands of short-exposure images, and carefully processing the data, researchers could cancel out almost all of the blurring.

“This result shows that given the right conditions an 8.1m telescope pushed to its limits can rival not only the Hubble Space Telescope when it comes to angular resolution, but also the James Webb Space Telescope,” Ricardo Salinas, a co-author of study, 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,” Dr Salinas said.