After many years obscured by dust and gas, the largest young star cluster in the Milky Way – Westerlund 1 – has finally been discovered by the James Webb Space Telescope (JWST).
This star cluster is located near the center of the Milky Way, directly beneath the tail of the Scorpius constellation, and can be observed from the Southern Hemisphere.
JWST’s view of Westerlund 1, one of the closest “super star clusters” to the Solar System. (Source: ESA/Webb)
Westerlund 1 is a prime example of a “super star cluster”, home to hundreds of massive stars. With a mass ranging from 50,000 to 100,000 times that of the Sun, this star cluster exceeds most other stellar clusters, which typically have a mass of around 10,000 times that of the Sun.
Some stars in Westerlund 1 are up to 2,000 times the size of the Sun. If one of these gigantic stars were in our Solar System, its reach could extend to the orbit of Saturn. Not only are these stars colossal in size, but they also shine up to a million times brighter than the Sun.
If Earth orbited a star from the Westerlund 1 cluster, our night sky would be illuminated by hundreds of brilliant stars, resembling the light of a full moon. This stunning scene is one of the factors that helps scientists gain deeper insights into the evolution of massive stars.
According to astronomers, Westerlund 1 is entering a particularly dynamic phase, and over the next 40 million years, more than 1,500 stars in the cluster will explode as supernovae – colossal explosions marking the end of the life cycle of massive stars. Currently, the star cluster is only about 3.5 to 5 million years old – a very young age in cosmic terms.
The latest images of Westerlund 1 provided by JWST have given astronomers unprecedented insights and comprehensive views.
Westerlund 1 as seen by JWST. (Source: ESA/Webb)
Unlike the Hubble Space Telescope, which is limited by its inability to observe through dust clouds, JWST, with its Near Infrared Camera (NIRCam), has overcome this challenge. NIRCam can capture infrared light, allowing it to “see through” the dust layers and reveal the mysterious details within the star cluster.
In the impressive images captured by JWST, red gas spirals are vividly visible at the top and center of the frame, while brilliant stars shine with diffraction spikes – a unique phenomenon created by the telescope’s mirror design.
These are characteristic images that only JWST can capture, opening the door for scientists to better understand the past and future of large star clusters in the universe.
Westerlund 1 is not only a cosmic wonder but also a crucial key for scientists exploring the formation and evolution of massive stars in the Milky Way.
Super star clusters like Westerlund 1 are very rare today. They are valuable traces that help decode the ancient history of the galaxy, thereby enhancing our understanding of how massive stars form and disappear.
