First ever black hole picture is hugely underwhelming compared to these theoretical impressions
With the Event Horizon Telescope (EHT) revealing the first real image of a black hole, we can say that we haven't been so wrong in our theoretical representations of the celestial phenomena. The highly anticipated revelation shows a hazy outline of light bending around the event horizon of a giant black hole at the center of the galaxy M87, and space geeks know this is a major breakthrough in our understanding of such all-consuming mass monsters lurking millions of light years from our tiny blue planet.
But how does the recently revealed image compare to impressions of black holes in the past? Previous renditions used by reputed agencies such as NASA and ESO were based on pure observational research and theoretical physics, and ultimately brought to life by highly skilled artists. Considering the "stellar" work done by our astronomers, it looks like we were pretty accurate. Here are some of the most famous black hole phenomena documented and illustrated before the EHT showed us the real thing.
1. The most distant black hole
In December 2017, scientists uncovered the farthest known supermassive black hole. Its mass is 800 million times that of our Sun, which is already stunningly massive for its young age. "This black hole grew far larger than we expected in only 690 million years after the Big Bang, which challenges our theories about how black holes form," said Daniel Stern of NASA's Jet Propulsion Laboratory in Pasadena, California, at the time.
In order to identify potential distant objects to study, astronomers combined data from NASA's Wide-field Infrared Survey Explorer (WISE) and Carnegie Observatories' Magellan telescopes in Chile with several ground-based surveys to support the study.
2. Black holes spewing massive jets of matter into the universe
The above image is a composite of data obtained from Hubble and a radio telescope. It shows jets of energy and matter being released out of the center of the Hercules A galaxy. The speed of the jet propulsion is almost at the speed of light, which gives us a clear idea of the monumental destructive power of these celestial phenomena.
3. Supermassive black holes will eat anything
The above illustration depicts a supermassive black hole devouring a star, forcing the release of a glowing stream of material from the latter. The ring of dust surrounding the black hole, as shown in the image, was previously illuminated by flares of high-energy radiation from the perpetually hungry black hole. The tail end shows some of that energy being re-radiated as heat in the infrared part of the light spectrum.
The stellar material of a star gets stretched and compressed if it passes within a certain distance of a black hole, and is eventually swallowed by it. This phenomenon is known as "stellar tidal disruption" and it releases huge amounts of energy, thereby illuminating the surroundings during a flare. These flares, although discovered and studied in the past, are yet to be well understood.
4. But not everything...
Some supermassive black holes fail to suck in a fraction of the matter falling toward them. Instead, they get pushed away from the core in the form of two narrow beams or "jets" in opposite directions, almost at the speed of light. These jets form along the black hole's axis of rotation (although not all black holes rotate) and are thought to be sources of high-energy cosmic rays.
Scientists are using a special telescope known as the Event Horizon Telescope (EHT) to attempt to see light surrounding the black hole right to the edge of the event horizon, which is possible theoretically. Before crossing the event horizon, matter orbiting a black hole can form a ring of light owing to its high speed. This ring is referred to as the black hole's shadow or silhouette.
5. Magnetic bloom
In April 2015, astronomers gained deeper insights into the structure and formation of supermassive black holes after observing an extremely powerful magnetic field very close to the event horizon.
Supermassive black holes are said to reside at the heart of almost all galaxies in the multiverse. These celestial giants have the potential to accrete huge amounts of matter in the form of a peripheral disk. A fraction of the matter is ejected as a jet of plasma, as mentioned before. However, the phenomenon is yet to be fully understood.
6. A mysterious disk floating in space
Gas falling into the gravitational well created by a massive black hole will usually form a disc-like structure around the object due to the conservation of angular momentum. Most artists' impressions such as the one above usually show the black hole as it if were a flat space body hiding part of the disc just behind it. However, in reality, the gravitational lensing has the potential to highly distort the image of the accretion disk.
7. This one does not rotate
While the shape of the event horizon of a black hole is always considered to be spherical, the Doppler effect changes the geometry according to its spin. If a black hole is non-rotating or static, the event horizon is precisely spherical.
However, the Doppler effect resulting from the extremely high orbital speed of a rotating black hole causes its event horizon to be oblate. The orbital speeds generated are needed for centrifugal balance of the very strong gravitational power of the hole.
8. Stellar death
In June 2018, astronomers directly imaged the formation and expansion of a fast-moving jet of material spewed when a supermassive black hole ripped a star apart after it wandered too close to the event horizon. Such stellar deaths or tidal disruption events (TDEs) are rarely detected.