Image courtesy of A. Smith, N. Madhusudhan (University of Cambridge
The universe
is wonderful. It speaks of the one who
made it. The James Webb space telescope has just pictures a cluster that is
some 3.7 million light years from us, in the constellation Carina.
However, it
does not mention how dark matter is distributed.
“Galaxy
clusters act as a magnifying lens, shining light on the faintest and most
distant objects — a phenomenon known as gravitational lensing. On the rarest of
occasions, galaxy clusters collide, creating an even more massive lens. The James
Webb Space Telescope (JWST) recently provided extremely detailed
observations of such a lens, the Bullet Cluster.
Located
about 3.7 billion light-years from Earth in the constellation Carina, the
Bullet Cluster is the aftermath of the collision between two galaxy clusters
that is estimated to have begun approximately 150 million years ago. Each of
the two galaxy clusters can be distinguished within the blue regions, yet they
are bound by gravity and together form a single entity — the Bullet Cluster.
While
gravitational lensing brings distant, faint objects into light, the extent of
lensing can reveal the mass distribution within the massive foreground galaxy
cluster. Mysterious dark matter makes up a huge chunk of
galaxy clusters, but is difficult to spot because it does not reflect, absorb
or emit light. So, astronomers sometimes study light from stars that are within
the galaxy cluster but are not part of any galaxies. These stars are called
intracluster stars and are floating because they are stripped from their
galaxies during collisions. By analyzing the light from these stars,
researchers can trace the distribution of dark matter, as these stars are
gravitationally bound to the cluster's dark matter.
The latest
data from JWST, combined with data from the Chandra X-ray Observatory, allowed
astronomers to create an accurate map of mass — both visible and dark matter —
within the Bullet Cluster. The light from intracluster stars pinned down the
location of invisible matter, and the X-rays confirmed the location of hot gas.
Based on these observations, astronomers could "replay" the
collision. This revealed that hot gas (in bright pink) was pulled out of the
galaxy clusters and left behind in the central region, while the dark matter
(in blue) associated with individual galaxy clusters stayed.”
Source:
Shreejaya Karantha 2025 Did the James Webb telescope really find evidence of alien life? Here's the truth about exoplanet K2-18b. | Live Science July 6
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