When galaxy clusters merge together, they form the largest objects the Universe will ever create.
“On a cosmic scale, our life is insignificant, yet this brief period when we appear in the world is the time in which all meaningful questions arise.”
Of all the astronomical, bound structures — planets, stars, galaxies, etc. — there’s none larger than a galaxy cluster.
The largest ones contain many thousands of times the mass of the Milky Way, both in terms of galaxies and dark matter.
The Universe forms a vast cosmic web where filaments interconnect, with matter flowing along them into a nexus.
At the centers of these intersections, the most massive galaxy clusters form.
Over time, more clusters fall in, creating the largest structures of all.
The Hubble Space Telescope recently observed one of them, MACS J0717, revealing four separate clusters in the collision process.
Additional X-ray data from Chandra shows that a huge filament feeds into this cluster, creating this unprecedentedly messy cosmic mashup.
Detailed radio observations show ultrafast shocks and, at the highest energies, supermassive black hole jets turned on in multiple separate galaxies.
One subcluster moves so quickly — 3,000 km/s — that the speedy electrons push background light to higher energies: the first direct observation of the kinetic Sunyaev-Zel’dovich effect.
Finally, weak gravitational lensing reveals separations between mass and X-rays: further indisputable proof of dark matter.
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