How do galaxies, like our own large, majestic, star-splattered Milky Way form, and how do they evolve through time? When we gaze in wonder up at the night sky above our planet, we see that it is dazzling with the distant fires of a host of brilliant stars. However, most of the Universe is dark, made up of exotic, transparent material, the identity of which constitutes one of the most profound and bewitching of all mysteries. In August 2015, a team of astronomers led by the California Institute of Technology (Caltech) in Pasadena, California, announced the discovery of a gigantic, whirling disk composed of gas that is a very remote 10 billion light-years away. This enchanting, bewildering, bewitching ancient structure is thought to be a galaxy-in-the-making–and it is actively being fed a nutritious formula of cool pristine, primordial gas that can be traced all the way back to the very beginning–the Big Bang birth of the Universe almost 14 billion years ago, and its discovery sheds new light on this great and profound mystery.
Using Palomar Observatory’s Cosmic Web Imager (CWI), that was designed and built by Caltech, the astronomers were able to image the distant protogalaxy and found that it is bound to a filament of the intergalactic medium–the great Cosmic Web that is constructed of diffuse gas that weaves its way between galaxies and extends throughout the entire Universe.
The enormous Cosmic Web is a large-scale, web-like structure that is embellished with the starry luminous fires of the galaxies, and it is thought to have played a major role in the evolution of galaxies that occurred long ago and far away in the ancient Universe–only a few billion years after the Big Bang.
The way that galaxies and matter are distributed in the Universe is not random. The distribution of galaxies, up to the present time, resembles an enormous network–the transparent Cosmic Web of ghostly invisibility–a strange transparent structure flecked with countless stars. This weird, ghostly web has denser regions composed of dazzling groups and clusters of galaxies. There are also regions that are dark web links almost–but not entirely empty–which are the cosmic voids. The filaments link the regions of greatest density, somewhat like bridges that connect the densest regions of the Cosmic Web. This filamentary structure has been compared to threads woven into the web.
Galaxies located in the regions of lesser density have a greater probability of actively giving birth to brilliant, new baby stars (protostars). In contrast, galaxies situated in denser regions give birth to their stellar inhabitants much more slowly. Our own Milky Way Galaxy is located in a region of lesser density.
The billions of starlit galaxies and enormous clusters of galaxies are embedded in mysterious, invisible halos of transparent, ghostly dark matter. Dark matter is a bizarre and bewildering form of exotic matter that is generally believed to exist because it exerts gravitational effects on objects that can be observed–such as galaxies that blaze with starlight and glowing clouds of gas. However, the true identity of the dark matter is unknown, even though it is the most abundant form of matter in the Universe. Dark matter is thought to be composed of exotic non-atomic particles that do not interact with light, or any other form of electromagnetic radiation. The starry galaxies are suspended throughout this invisible, enormous structure in a way that evokes the haunting image of glittering dewdrops on the web of a waiting spider.
Even more abundant, and more mysterious, is the dark energy–a strange substance that is causing our Universe to speed up in its expansion. Some scientists even propose that, billions and billions of years from now, the bizarre dark energy will tear our entire Universe apart–even ripping atoms into non-existence.
The most recent measurements suggest that the dark energy accounts for most of the mass-energy of the Cosmos–68.3% of it. The dark matter accounts for 26.8% of the Universe, while familiar atomic matter–the stuff of planets, moons, people, and literally all of the elements listed in the Periodic Table of the Elements–accounts for a mere 4.9% of the Cosmos. The runt of the Cosmic litter, so-called “ordinary” atomic matter, is really very extraordinary. Without it, life would not be possible.
Most astronomers think that the Cosmos was born about 13.8 billion years ago in the Big Bang. It began as an unimaginably tiny Patch, that was smaller than an elementary particle, and then–in the briefest instant–expanded exponentially to reach macroscopic size. Something–it is not known precisely what--caused that very small Patch to experience this wild period of inflation. This little Patch, that was too small for a human being to see with the naked eye, was so exquisitely tiny that it was almost, but not quite, nothing–and it was so extremely hot and dense that everything that we are, and everything that we know, originated from it.
The neonatal Universe was filled with energetic radiation, a violent, stormy sea of searing-hot particles of light, that we call photons. The entire baby Cosmos was brilliant with light, and it resembled the glaring, blinding surface of a star. What we now witness almost 14 billion years after our Universe’s mysterious birth, is the dimming and greatly expanded and still-expanding aftermath of that primordial birth. As our Universe evolved and grew to its present unimaginably enormous size, the ancient fires of its birth cooled–and now we bear witness as we watch from our tiny, rocky, obscure little planet as our Universe grows ever larger and larger, darker and darker, colder and colder, fading like the lingering, eerie, haunting grin of the Cheshire Cat in a Wonderland dream.
The most widely accepted theory suggests that the Universe, at the instant of its birth, underwent a brief period of accelerated expansion termed inflation. Even though inflation still remains in the realm of theory, the most recent measurements and observations show that it is the most likely explanation known that could have caused the Cosmos to evolve in the way that it has over the course of billions and billions of years. In the smallest fraction of a second, it is thought that inflation blew up like an extraordinary bubble each and every region of our tiny Patch of space by a factor of at least 10 to the 27th power–that is, 10 followed by 26 zeroes. Before inflation enlarged this Patch, the region of the Universe that we can observe today–the visible Universe–was a smooth little bit that was smaller than a proton. At this very ancient era, our Cosmos was composed of a strange plasma of elementary particles. Speedy, high-energy photons slowly lost their energy as time went by and started to travel more slowly. In other words, they cooled off as the Universe continued to expand. The energy flowed into the expansion. In the almost 14 billion years since our Universe was born, it has expanded by yet another 10 to the 27th power.