Astronomers have released what could be the historic first images of a supermassive black hole's event horizon. The enormous black hole is located within the large galaxy M87, and was imaged by a network of powerful observatories that formed a single planet-sized virtual telescope.
Black holes are believed to be regions of space where matter is packed so densely that nothing can escape their gravitational influence. Not even light. They are cosmic leviathans, capable of shredding and devouring entire solar systems, and while a veritable library of scientific papers has been penned on their nature, they remain one of the most enigmatic phenomena populating the universe.
There is evidence to suggest that supermassive black holes lurk at the center of most large galaxies. These cosmic heavyweights dwarf the more common breed of black holes created in the death throes of enormous stars, and are thought to play an important role in galactic evolution.
At the heart of the Milky Way, some 26,000 light-years from Earth in the direction of the galactic center lies our own supermassive black hole, Sagittarius A*(Sgr A*). This monster has a mass the equivalent of 4 million Suns crammed into an area 30 times the size of our parent star, and whether you realize it or not you have been travelling around it your entire life.
Humanity's eagerness to understand the phenomena is hampered by the fact that we cannot directly observe a singularity in the same way we might image a planet, as it emits no light, and allows none to escape. One of the ways that scientists can attempt to understand a black hole is by observing the space environment surrounding a singularity, including its event horizon, which is essentially the line of demarcation beyond which nothing can escape its gravity.
Today, an international team of over 200 astronomers has released the first direct images ever captured of what is believed to be a black hole.
The data used to create the images was captured back in April 2017 using a network of eight connected radio telescopes positioned around the globe known collectively as the Event Horizon Telescope (EHT). Working together, the array forms a single virtual observatory the size of the Earth, with an impressive angular resolution of 20 arc microseconds, which is roughly 3 million times sharper than that of a healthy human eye.
To put it differently, if an equivalent resolution were applied to the human eye, a person would be capable of reading a text message on a phone in New York while standing on a street in Paris.
Back in 2017, the EHT targeted the supermassive black hole sitting at the heart of the galaxy M87, which is located in the Virgo galaxy cluster some 55 million light-years from Earth.
The results of these observations are only now being released owing to the fact that the vast quantities of information captured during the campaign couldn't possibly be transferred over the internet. Instead, the data had to be transported on hard drive to two central processing facilities in the USA and Germany, where they were carefully calibrated, synchronized and combined with the help of a supercomputer.
Once the data was verified, it was sent out to four independent teams who were individually tasked with creating a finished image using different algorithms. Each team had previously verified its techniques using other cosmic objects to make sure that an accurate visual representation would be created. With a sigh of relief, all four teams produced finished images displaying the same distinctive structure.
The release shows what appears to be a lopsided ring of fire surrounding a dark, circular center. This ring is made up of superheated material falling toward the black hole's event horizon, the border of which is visible where the interior of the ring abruptly stops. What lies within is the black hole's "shadow," which is caused by the gravitational bending and capture of light by the event horizon.
Based on its observations, the team estimates that the monster black hole has a mass the equivalent to 6.5 billion Suns.
The images potentially prove the existence of event horizon features that had been theorized around black holes. All of the elements revealed in the image were also found to follow closely with black hole features predicted in Albert Einstein's theory of general relativity.
The unusual lopsided appearance of the ring of fire is likely due to the clockwise rotation of either the black hole, or the material that forms the feature.
"This black hole is much bigger than the orbit of Neptune, and Neptune takes 200 years to go around the Sun," says Geoffrey Crew, a research scientist at MIT's Haystack Observatory in Massachusetts. "With the M87 black hole being so massive, an orbiting planet would go around it within a week and be traveling at close to the speed of light."
Moving forward the team hopes to finish calibrating a similar image of Sgr A*, which was also imaged by the EHT back in 2017.
The video below zooms in on the newly-imaged supermassive black hole from the perspective of Earth.
Six papers have been published in a special edition of the Astrophysical Journal Letters.
Source: MIT
