Today marks the 25th anniversary of the NASA/ESA Hubble Space Telescope’s launch, and the instrument’s science team is marking its silver anniversary by releasing a brand new image of the star cluster Westerlund 2, located 20,000 light-years away in the constellation Carina.
It was April 24, 1990 when Hubble was first sent into orbit aboard space shuttle Discovery, and over the past quarter-century, it has “reached and surpassed all expectations,” the Hubble team said in a statement, “beaming back data and images that have changed scientists’ understanding of the Universe and the public’s perception of it.”
The subject of the new Hubble photo, Westerlund 2, is a large cluster of approximately 3,000 stars that is part of a highly active stellar breeding ground known as Gum 29. The cluster is typically hard to observe because it is obscured by dust, but Hubble’s Wide Field Camera 3 instrument is powerful enough to sneak a peek through that veil in near-infrared light.
“This image is a testament to Hubble’s observational power and demonstrates that, even with 25 years of operations under its belt, Hubble’s story is by no means over,” they added, noting that it will at least temporarily work alongside its successor, the James Webb Space Telescope, after the latter launches in 2018.
Young cluster is home to bright, hot, massive stars
The new image clearly shows the central cluster, which is only about 10 light-years across but is densely packed with stars. Westerlund 2 is believed to be just two million years old, but is nonetheless home to “some of the brightest, hottest and most massive stars” discovered to date, according to the Hubble research team.
A few of the biggest, most massive stars are said to be giving off streams of ultraviolet light and charged particles known as stellar winds, which are tearing holes in the material surrounding the cluster. As a result, the hydrogen gas cloud in which its stars were originally formed are starting to be eroded.
The gas-and-dust monoliths depicted in the image have thus far been resisting the powerful stellar winds and the radiation, the researchers noted. These pillar-like structures, which are a few light-years tall, point to the central cluster. The pillars are also surrounded by additional dense regions, including dark filaments of dust and gas, they added.
“Besides sculpting the gaseous terrain, the brilliant stars can also help create a succeeding generation of offspring,” the Hubble team said. “When the stellar winds hit dense walls of gas, they create shocks, which generate a new wave of star birth along the wall of the cavity. The red dots scattered throughout the landscape are a rich population of forming stars that are still wrapped in their gas and dust cocoons.”
Those still-forming stars have not yet ignited the hydrogen in their cores, and as such have not yet started to illuminate as stars. However, they were able to identify these stellar fetuses using the telescope’s near-infrared vision. The bright blue stars that also appear in the new image are primarily located in the foreground, the astronomers explained.