The picture itself is breathtaking. But what we learn is truly eye-opening.
Galaxy clusters, like the massive one captured here by Hubble, PLCK G004.5–19.5, impress not just for their looks, but for their science.
Out there in the depths of space, collections of thousands of galaxies have formed over billions of years from gravity’s relentless pull.
These are the largest bound structures of all, as dark energy will drive the apparently larger “superclusters” apart.
If you map out the motions of the galaxies inside the cluster, you can derive the total cluster mass.
Most of the mass is in between the galaxies, proving that there’s unseen matter in the cluster.
We find these clusters from the hot, intergalactic gas that shifted the background light left over from the Big Bang.
There’s more gravity than the gas can provide, showing the presence of non-baryonic dark matter.
But all the mass, combined, contributes to gravitational lensing.
The bending of space stretches and magnifies the light from galaxies behind the cluster.
This is the whole purpose of the joint Hubble/Spitzer RELICS program, highlighted by this galaxy cluster.
Gravitationally lensed galaxies are the most distant ever identified.
Through this process, RELICS can reveal the perfect observing targets for the James Webb Space Telescope.
Mostly Mute Monday tells the astrophysical story of an object, picture, or phenomenon in images, visuals, and no more than 200 words.Ethan Siegel is the author of Beyond the Galaxy and Treknology. You can pre-order his third book, currently in development: the Encyclopaedia Cosmologica.