A study shows that the largest star in the universe is smaller than thought

Posted in: 20/08/2022 – 10:48Last updated: 20/08/2022 – 10:46

Paris (AFP) – It turned out that the largest star observed in the universe is not the size that was previously estimated, as new observations showed, which is likely to apply to other large stars.

The star “R136a1” is located in the Tarantula Nebula, among a group of stars in the so-called Magellanic Cloud, near the Milky Way, which includes Earth, and its discovery dates back to 1985. In 2010, a team of astronomers classified it as the largest star The size of the one that has ever been observed so far, as its mass exceeds the size of the sun by 320 times, but previous modern observations forced a modification of these estimates, as it showed that its size is only 250 times greater than the sun.

In the latest study to be published in the Astrophysical Journal, a team using the Gemini North in Hawaii and the South Gemini telescope in Chile lowered its mass estimate to between 170 and 230 solar masses.

“Our results show that the most massive star we currently know is not as massive as we thought,” said the study’s lead author, an astronomer at the US NOIRLab, who operates the Gemini telescope and Venu Kalari.

“This indicates that the upper limit of the stellar mass may also be smaller than we thought,” he added in a statement issued by the center Thursday.

It is difficult to observe the largest and brightest stars in the universe, such as “R136a1”.

This is due firstly to the fact that its life span is relatively very short, as it is limited to a few million years, while the life span of the Sun is ten billion years.

The second reason is that they are generally located within compressed star groups enveloped by stellar dust, which makes it difficult to accurately measure their brightness, knowing that it is precisely this brightness that allows determining the mass of the star.

The Neuer Lab team obtained the most accurate image of the stars in the group, and thus of the star “R136a1”, using a technique called interferometry. The center’s “Zoro” imaging device took a very large number of pictures, amounting to 40,000, with a very short exposure time, which enabled it to avoid blurring the Earth’s atmosphere on the footage.

Given that the observation technique used has not previously been applied to this type of target, the study authors treat its results “with caution”, according to Kalari, waiting for more efficient tools to allow improvement of measurement, such as the Extremely Large Telescope (ELT), which is expected to enter service in the next year. 2027.

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