Image: Hubble's galaxy cluster cornucopia
At first glance, this image is dominated by the vibrant glow of the swirling spiral to the lower left of the frame. However, this galaxy is far from the most interesting spectacle here鈥攂ehind it sits a聽galaxy cluster.
Galaxies are not randomly distributed in space; they swarm together, gathered up by the unyielding hand of gravity, to form groups and clusters. The Milky Way is a member of the聽Local Group, which is part of the聽Virgo Cluster, which in turn is part of the 100,000-galaxy-strong聽Laniakea Supercluster.
The galaxy cluster seen in this image is known as SDSS J0333+0651. Clusters such as this can help astronomers understand the distant鈥攁nd therefore early鈥攗niverse. SDSS J0333+0651 was imaged as part of a study of聽star formation聽in far-flung galaxies.
Star-forming regions are typically not very large, stretching out for a few hundred light-years at most, so it is difficult for telescopes to resolve them at a distance. Even using its most sensitive and highest-resolution cameras, Hubble can't resolve very distant star-forming regions, so astronomers use a cosmic trick: they search instead for galaxy clusters, which have a gravitational influence so immense that they warp the聽space-time聽around them.
This distortion acts like a lens, magnifying the light of galaxies (and their star-forming regions) sitting far behind the cluster and producing elongated arcs like the one seen in the upper left part of this image.
Provided by NASA