Hubble reveals details of the Westerlund 2 star cluster

Hyperaxion May 28, 2020

Discs surrounding the stars near the center of the system are devoid of the large, dense clouds of dust that should exist there.

Using information collected by the Hubble Space Telescope over the past three years, NASA and ESA astronomers have discovered more information about the star cluster Westerlund 2, located in the constellation Carina, in the Milky Way. The findings were shared on Thursday (28) on the official Hubble website.

Hubble reveals details of the Westerlund 2 star cluster
(Credit: NASA, ESA, the Hubble Heritage Team).

The research found that the disk surrounding the stars near the center of the cluster is devoid of the large, dense clouds of dust expected to exist there. According to experts, this is due to the presence of massive stars in the region.

That’s because the stars emit intense ultraviolet radiation and stellar winds similar to hurricanes. Together, these phenomena act as a “blowtorch” and corrode matter in the surroundings, dispersing clouds of galactic dust.

“With an age of less than about two million years, Westerlund 2 harbours some of the most massive, and hottest, young stars in the Milky Way,” said Danny Lennon, one of the researchers, in a statement. “The ambient environment of this cluster is therefore constantly bombarded by strong stellar winds and ultraviolet radiation from these giants that have masses of up to 100 times that of the Sun.”

In addition, astronomers have found that these conditions prevent the formation of planets in Westerlund 2, as these objects need huge clouds of dust to form. “Basically, if you have monster stars, their energy is going to alter the properties of the discs,” explained Elena Sabbi, who also participated in the discovery. “You may still have a disc, but the stars change the composition of the dust in the discs, so it’s harder to create stable structures that will eventually lead to planets.”

Westerlund 2 in the night sky.
Westerlund 2 in the night sky. (Credit: NASA, ESA, Digitized Sky Survey 2).

Of the nearly 5,000 stars observed in Westerlund 2 with masses between 0.1 and five times that of the Sun, 1500 showed fluctuations in their luminosity, which suggests the presence of stardust. According to scientists, the material in orbit temporarily blocks part of the light emitted by the stars, causing fluctuations in its brightness.

Thanks to new analyzes carried out with Hubble, the group noticed these oscillations only in stars located at least four light-years from the center of the cluster. “We think they are planetesimals or structures in formation,” explained Sabbi. “These could be the seeds that eventually lead to planets in more evolved systems.”


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