Black Holes
The black holes of Nature are the most perfect macroscopic objects there are in the universe: the only elements in their construction are our concepts of space and time. ~ Indian astrophysicist Subramanyan Chandrasekhar
A black hole is a cosmic singularity of no return once within, past the event horizon that defines entrance into a black hole.
The event horizon is not a physical barrier. ~ Scottish astrophysicist Paul McNamara
Most matter drawn into a black hole is spun off before it reaches the event horizon. This expelled energy flow is termed a quasar when the emitted radiation is luminous (light and infrared warmth being the only spectral range of radiation celebrated by humanity).
A black hole grows as matter is absorbed. However logical that seems, how it happens is not known. The mystery emanates from the nature of the singularity. A black hole is literally a perfectly spherical hole in the universe – spacetime simply ceases to exist.
It is bizarre that these infinite voids provide for the gyre of existence by anchoring galaxies and driving their dynamics. As Lao Tzu stated: what is not makes what is useful.
◊ ◊ ◊
Black holes and their host galaxies coevolve, with the feedback from the black hole inducing star formation. ~ Israeli astronomer Benny Trakhtenbrot et al
Small density fluctuations in the early universe led to perturbations that sprouted in the fertile ground of gravity. These grew to the point that they disconnected from the global expansion of the universe. Such centers became self-gravitating; forming halos within which gas condensed to form stars, black holes, and galaxies.
Black holes have peppered the cosmos since its salad days. They were abundant in the early universe; swapping the beginning of something for a gaping maw of nothing. These seeds of nothingness grew by consuming whatever fell into their path.
One black hole has a mass 12 billion times that of the Sun, accreting surrounding substance at the maximum rate afforded by the laws of physics. This black hole had an awesome girth 12.92 bya, only 900 million years after the supposed Big Bang. Other contemporaneous monstrous black holes have been found. Astrophysicists have no explanation for how such massive black holes were possible so early in the cosmos’ supposed history.
We expected as we looked further back into time that the black holes would be smaller and smaller because they hadn’t had as much time to grow. ~ American astrophysicist Rob Simcoe
The existence of massive black holes just hundreds of millions of years after the Big Bang strongly indicates that the conventional dating of this universe’s birth is wrong. The cosmos must be much older.
Black holes were the nursery in which early galaxies grew up; both a great attractor and generator of galaxy-making material. Black holes were more massive relative to their respective galaxies when the universe was young.
Besides the intense implosion of a massive gas cloud, a black hole can form after a supernova explosion, with the remnants collapsing, forming a forceful gravitational pull that sucks in surrounding mass in an ongoing accretion process.
Black holes are everywhere and come in all sizes. Some are swollen to 50 billion times the mass of the Sun.
A massive black hole is a gyre, gaining girth and power while emitting energetic streams that may stretch for millions of light-years. A star coming close to a supermassive black hole may be ripped apart by the hole’s tidal pull, with stellar debris spun off as a quasar.
There is an ancient quasar at the edge of the observable universe that appears to be 12.9 billion years old, powered by a black hole of 2 billion solar masses. The quasar emits 60 trillion times the light of the Sun.
This enhancement of star formation by outflows would have been even more important in a younger universe, where dense clumps of gas were much more common. ~ Australian astrophysicist Stanislav Shabala
Black holes typically account for 0.1% of a galaxy’s mass, but one has been observed that is a whopping 14% of galactic girth.
A spinning black hole draws matter that rotates around it. On the way to a black hole, incoming material picks up its pace. In the competition between speed and gravity, speed wins. Over 99% of the matter drawn to black holes is ejected.
Feasting makes a black hole faster. The larger the black hole, the quicker its spin. A supermassive black hole at the center of a nearby galaxy has been clocked at 1.08 billion kilometers per hour: close to the speed of light. Black holes continuously spew cosmic rays, the most energetic radiation in the universe.
Galaxies and black holes have grown in tandem throughout cosmic history. There is a correlation between the mass of a galaxy’s central black hole and the velocity of stars in its galaxy. All the galaxies near the Milky Way have about 700 times more mass in their stellar bulges than deposited in their black holes, irrespective of the galaxy’s size. This appears to be an evolved situation.
The Milky Way grew by capturing dwarf galaxies which had originally formed from black holes. The galactic merger process can result in a dwarf black hole recoiling rather than merging with the massive black hole at the heart of the Milky Way. More often, galaxies are joined as their black holes interact.
When black holes encounter one another, they dance together for a while in a close embrace. The footfalls of black hole ballet are gravitational waves that ripple spacetime itself. These waves carry for untold light-years, creating a web of galactic interactions. Eventually, the black holes merge into one – their mutual gravitational attraction irresistible.
Black holes are not confined to being center stage in the galaxy. Galaxies may have millions of black holes roaming about, each with the mass of anywhere from 1,000 to 100,000 suns, swallowing anything in their path, shaping galactic dynamics. There an estimated 400 million black holes in the Milky Way galaxy.
While black holes often engender galactic formation, they can also slowly suffocate galaxies. The spin of a black hole determines what role it plays in the galaxy about it.
The lives of galaxies and their supermassive black holes are inextricably intertwined. ~ American astrophysicists Timothy Heckman & Guinevere Kauffmann
As matter is sucked toward a black hole, a disk of infalling gas and dust forms around the rim. On the journey inwards, owing to quantum effects, incoming debris emits large amounts of X-ray and ultraviolet radiation; radiation so strong that it diverts part of the inflow. This causes strong outflowing winds, with velocities up to several hundreds of kilometers per second.
Outflowing jets from massive black holes engender star formation by plowing through galactic gas, thereby creating hot gas filaments, the raw material from which stars form. A black hole’s energetic jet causes a supersonic shock wave on a gas cloud in its path, heating and compressing the gas.
The shock wave ionizes the gas cloud: stripping electrons from the gaseous atoms. After the shock wave subsides, the ions recombine, emitting radiation, which takes energy out of the cloud. This cooling effect causes the gas cloud to contract further. When the knot of gas reaches a critical density, it collapses to form a star.
