(click on image to enlarge)
From NASA/ ESA, May 6, 2026:
Astronomers have long known that understanding how star clusters come
to be is key to unlocking other secrets of galactic evolution. Stars
form in clusters, created when clouds of gas collapse under gravity. As
more and more stars are born in a collapsing cloud, strong stellar
winds, harsh ultraviolet radiation and the supernova explosions of
massive stars eventually disperse the cloud, and their light can bear
down on other star-forming regions in the galaxy. This process is called
stellar feedback, and it means that most of the gas in a galaxy never
gets used for star formation. Researching how star clusters develop can
answer questions about star formation at a galactic scale.
Now, the state of the art has been further developed with both Hubble
and Webb working together to provide a broad-spectrum view of thousands
of young star clusters. An international team of astronomers has pored
over images of four nearby galaxies from the FEAST observing programme
(#1783),
trying to solve this mystery. Their results show that it is the most
massive star clusters that clear away their gaseous shroud the fastest,
and begin lighting their galaxy the earliest.
The team identified nearly 9000 star clusters in the four galaxies in
different evolutionary stages: young clusters just starting to emerge
from their natal clouds of gas, clusters that had partially dispersed
the gas (both from Webb images), and fully unobstructed clusters visible
in optical light (found in Hubble images). With Webb’s ability to peer
inside the gas clouds, they were able to then estimate the mass and age
of each cluster from its light spectrum.
This image shows a section of one of the spiral arms of Messier 51
(M51), one of the four galaxies studied in this work, as seen by Webb’s
Near-Infrared Camera (NIRCam). The thick clumps of star-forming gas are
shown here in red and orange, representing infrared light emitted by
ionised gas, dust grains, and complex molecules such as polycyclic
aromatic hydrocarbons (PAHs). Within these gas complexes, each tens or
hundreds of light years across, Webb reveals the dense, extremely bright
clusters of massive stars that have just recently formed. The countless
stars strewn across the arm of the galaxy, many of which would be
invisible to our eyes behind layers of dust, are also laid bare in
infrared light.
[Image description: A large, long portion of one of the
spiral arms in galaxy M51. Red-orange, clumpy filaments of gas and dust
that stretch in a chain from left to right comprise the arm. Shining
cyan bubbles light up parts of the gas clouds from within, and gaps
expose bright star clusters in these bubbles as glowing white dots. The
whole image is dotted with small stars. A faint blue glow around the arm
colours the otherwise dark background.]
Credit: ESA/Webb, NASA & CSA, A. Pedrini, A. Adamo (Stockholm University) and the FEAST JWST team
