The most massive known star in the universe just got its best close-up ever, revealing that the star might be smaller than astronomers previously thought.
Astronomers using the Gemini South telescope in Chile photographed the star R136a1which is about 160,000 light years from Earth in the center of the Tarantula Nebula in the Large Magellanic Cloud — a dwarf companion galaxy to the Milky Way. Their observations show that the giant star (and others like it) may not be as massive as previously thought.
“Astronomers have yet to fully understand how the most massive stars, those more than 100 times the mass of the Sun, form,” according to a statement (opens in a new tab) from the National Science Foundation (NSF) NOIRLab, which operates the Gemini South telescope. “A particularly difficult piece of this puzzle is obtaining observations of these giants, which typically reside in the densely populated hearts of dust-shrouded star clusters.”
Related: What is the most massive star?
Gemini South’s Zorro instrument uses a technique known as speckle imaging, which combines thousands of short-exposure images of stars deep in the universe to cancel the blur effect of earth’s atmosphere. This technique allowed astronomers to more precisely separate the brightness of R136a1 from its nearby stellar companions, resulting in the sharpest image of the giant star ever acquired.
While previous observations suggested that R136a1 was between 250 and 320 times more massive than the groundZorro’s new observations show that the mass of the giant star may be closer to 170 to 230 times that of the sun, still making it the most massive star known.
“Our results show us that the most massive star we currently know is not as massive as we previously thought,” study lead author Venu M. Kalari, an astronomer at NSF’s NOIRLab, said in the statement. “This suggests that the upper limit on stellar masses may also be smaller than previously thought.”
A the brightness of the star and temperature is based on its mass. In other words, more massive stars appear brighter and hotter. Astronomers estimated the mass of R136a1 by comparing its observed brightness and temperature with theoretical predictions. Because the new images of Zorro more precisely separated the brightness of R136a1 from its nearby stellar companions, astronomers were able to estimate that the star has a lower brightness and, in turn, a lower mass than the previous measures, according to the statement.
Massive stars like R136a1 grow rapidly, burning through their fuel reserves in just a few million years before dying a fiery death in supernova explosions, what then galaxies with heavy elements responsible for the formation of new stars and planets. This is the fate of most stars that are more than 150 times the mass of the Sun. However, if stellar masses are smaller than previously thought, supernovae may also be rarer than expected, the researchers noted.
The study has been accepted for publication (opens in a new tab) in The Astrophysical Journal.
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