Dark Matters About Primordial Black Holes

The Universe is a bewitching, mesmerizing mystery, an almost unfathomable puzzle that cannot be simply ignored, as it sings its haunting siren’s song to those who seek to understand its weirdness. Black holes are some of the weirdest denizens of our bizarre Cosmic Wonderland, with gravitational forces so extremely powerful that absolutely nothing, nothing, nothing at all–not even light–can escape from the furious, fatal claws of these strong gravitational beasts. Our Universe is thought to Black Travel have been born in the wild inflation of the Big Bang almost 14 billion years ago, when it began as an incredibly dense Patch, smaller than a proton, to experience exponential expansion–ballooning to attain macroscopic size in the smallest fraction of a second. Primordial black holes are hypothetical objects that may have formed as a result of the extreme density of matter present during the Universe’s ancient expansion. In May 2016, astronomers proposed that the mysterious substance known as the dark matter–that composes most of the matter content of the Universe–may be made of primordial black holes that formed during the first second of our Universe’s existence.

Our Universe is composed of approximately 68% dark energy, 27% dark matter, and 5% of the so-called “ordinary” atomic (baryonic) matter that makes up our familiar world. Dark energy accounts for the lion’s share of the Cosmos, and it is an unknown substance–likely a property of Space itself–that is causing our Universe to accelerate in its relentless expansion. The dark matter is commonly thought to be composed of exotic, non-atomic particles that do not interact with light or any other form of electromagnetic radiation–and is, therefore, transparent and invisible. However, scientists strongly suspect that it is really there, because it influences objects that can be observed–such as stars and galaxies–through the force of gravity. So-called “ordinary” atomic matter, which is really very extraordinary, is the runt of the Cosmic litter–but “good things come in small packages.” Atomic matter is the stuff of planets, moons, trees, and people–it is the stuff that brought our familiar Universe to life, and it represents all of the elements listed in the familiar Periodic Table. Only hydrogen, helium, and traces of beryllium were born in the Big Bang (Big Bang nucleosynthesis)–all of the rest of the atomic elements were cooked up by the stars (stellar nucleosynthesis), by way of the process of nuclear fusion. We are here because the stars are here. We are star dust.

Even though dark matter is generally thought to be composed of some exotic, non-atomic particles, the new research does present an intriguing alternative in the form of primordial black holes. Dr. Alexander Kashlinsky of NASA’s Goddard Space Flight Center in Greenbelt, Maryland, proposes that this interpretation fits well with our scientific knowledge of cosmic infrared and X-ray background glows that may explain the surprisingly high masses of merging black holes detected in 2015.

“This study is an effort to bring together a broad set of ideas and observations to test how well they fit, and the fit is surprisingly good. If this is correct, then all galaxies, including our own, are embedded within a vast sphere of black holes each about 30 times the Sun’s mass,” Dr. Kashlinsky explained in a May 24, 2016 NASA Press Release.

According to the Big Bang model, the temperature and pressure of the primordial Universe were so high soon after its birth that simple fluctuations occurring in the density of matter could have caused local regions that were dense enough to form black holes. Even though other regions of high density would have been rapidly scattered by the expansion of the Universe, a large enough primordial black hole might be stable enough to survive to the present.

In 1974, Dr. Stephen Hawking of the University of Cambridge in the UK, proposed that one way to spot primordial black holes would be by their Hawking radiation. The Hawking radiation is the emission by a black hole of virtual particle pairs in the powerful gravitational field surrounding a black hole. If the virtual particle pair survives long enough for one to travel outward, while its mate is pulled into the black hole, it would appear that the black hole is emitting radiation. A virtual particle is a short-lived fluctuation that exhibits a number of characteristics of an ordinary particle, but is transient–it is really not a particle at all.

Dr. Hawking theorized that a large population of small primordial black holes could possibly exist in our Milky Way Galaxy’s halo region. All black holes are theorized to emit Hawking radiation at a rate that is inversely proportional to their mass. Because this emission would further decrease their mass, black holes with a very small mass would undergo rapid runaway evaporation. This runaway evaporation could result in a massive blast of radiation at the end, and this would be equivalent to a hydrogen bomb yielding millions of megatons of powerful explosive force.

A common, garden variety stellar mass black hole, of about 3 solar-masses, is not able to shed all of its mass within the current age of the Universe–it would require an almost unimaginable 10 to the 69th power years to accomplish this feat. However, because primordial black holes are not born as a result of stellar core collapse, they may be of any size at all. Indeed, if low-mass primordial black holes formed in sufficient numbers during our Universe’s Big Bang birth, astronomers should be able to spot some that are relatively close to our own Galaxy, that are in the process of exploding today. NASA’s Fermi Gamma-ray Space Telescope, launched in 2008, is partly constructed to be able to hunt for evaporating primordial black holes. However, if the still-theoretical Hawking radiation does not really exist, such ancient black holes might be impossible to detect in space. This is because of their small size and their inability to exert a sufficiently powerful gravitational influence on objects that can be observed. Yet another way to spot primordial black holes would be by observing ripples on the surfaces of stars–if a black hole passed through a star, its density would cause vibrations that would be observable.

Because a primordial black hole does not necessarily have to be small–they can be of any size–they may also have been partly responsible for the later formation of galaxies.

Dark Matters In The Primeval Cosmos

There are more than 100 billion galaxies inhabiting our observable Universe. The observable Universe is that comparatively small region of the entire unimaginably vast, and unobservable Cosmos, that astronomers are able to see. Most of the Universe lies far beyond the reach of our visibility because the light being emitted from luminous objects in those incredibly remote regions has not had sufficient time to travel to us since our Universe was born in the Big Bang. This is because of the expansion of Space.

Before the first stars had ignited, shedding their light upon what had previously been a swath of featureless darkness, our Universe was a barren expanse. In our primeval Cosmos, opaque clouds composed primarily of pristine hydrogen gas collected along heavy, massive filaments of what is called the Cosmic Web, which is composed of the mysterious, unidentified dark matter. The invisible Cosmic Web weaves it way throughout Space and Time–and if it could be seen, it would look like an enormous web spun by a gigantic spider.

In the primeval Universe, dense regions of the Cosmic Web, composed of the ghostly, invisible dark material, gravitationally grabbed at traveling clouds of ancient, pristine hydrogen gas. Because dark matter can interact with electromagnetic radiation through the force of gravity, it warps, bends, and distorts traveling light (gravitational lensing). Gravitational lensing is nature’s gift to observers who can use it to see celestial objects that otherwise could not been observed. A prediction of Albert Einstein’s Theory of General Relativity (1915), gravitational lensing’s distortion of wandering light has lens-like effects, and it results in some very strange things. For example, this Spacetime warpage can create multiple images of a single object, such as a galaxy, or magnify an object, like a remote star, making it possible for it to be observed.

The strange phantom-like clumps of mysterious dark matter clutched at clouds of ancient, pristine gases, floating aimlessly in the direction of its invisible gravitational grasp. These ancient clouds became the cradles for the very first generation of baby stars to blast the Universe with their dazzling light.



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