BY ESA/HUBBLEJULY 8, 2025
A colossal cluster of galaxies is bending the very fabric of spaceÄand it's
the focus of this week's breathtaking image from the Hubble Space Telescope. Known as Abell 209, this enormous cluster lies about 2.8 billion light-years away in the constellation Cetus, also called The Whale.
Hubble's image reveals more than a hundred galaxies glowing within the
cluster, but what's visible is only part of the story. These galaxies are separated by vast distances, millions of light-years apart, and the space between them isn't empty. It's filled with scorching, diffuse gas that only shows up in X-ray observations. Even more mysterious is the presence of dark matter, an invisible form of matter that doesn't interact with light yet
makes up a huge portion of the Universe. In fact, scientists estimate the cosmos is made of about 5% normal matter, 25% dark matter, and 70% dark energy.
By observing clusters like Abell 209, astronomers are able to study some of the Universe's biggest mysteries, including dark matter and dark energy. These galaxy clusters are so massive they actually bend space itself, distorting the light from more distant galaxies behind them. This phenomenon, called gravitational lensing, acts like a natural cosmic magnifying glass, allowing scientists to study galaxies that would otherwise be too faint or far away to see.
While this image lacks the dramatic rings that gravitational lensing can sometimes create, Abell 209 still shows subtle signs of lensing at work, in the form of streaky, slightly curved galaxies within the cluster's golden glow.
By measuring the distortion of these galaxies, astronomers can map the distribution of mass within the cluster, illuminating the underlying cloud of dark matter. This information, which Hubble's fine resolution and sensitive instruments help to provide, is critical for testing theories of how our Universe has evolved.
Jerry
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