It is a historic day for astronomy. The Event Horizon Telescope has taken the first photo of a black hole.
The study, which was announced today in a series of six scientific papers published in a special issue of The Astrophysical Journal Letters, presents the image of the black hole located at the center of the massive galaxy Messier 87 , located 55 million feet away. light years from Earth with a mass 6.5 billion times that of the Sun.
“We have taken the first photograph of a black hole,” said EHT project director Sheperd S. Doeleman of the Harvard-Smithsonian Center for Astrophysics. “It is an extraordinary scientific feat accomplished by a team of more than 200 researchers.” It is worth noting that the “development” of the photograph has taken two years.
Black holes, extraordinary objects
With enormous masses but extremely compact sizes , their presence warps space-time and overheats any surrounding material.
Experts have discovered through multiple calibration and imaging methods the presence of a ring-shaped structure with a dark central region, basically the shadow of the black hole, which persisted during several independent observations carried out by the EHT.
Observations match predictions
“When we were sure that we had captured the image of the shadow , we were able to compare our observations with an extensive library of computational models that include the physics of curved space, super hot matter, and strong magnetic fields. Many of the structures in the image match surprisingly well with the theoretical prediction , ”comments EHT Board Member Paul TP Ho, Director of the East Asia Observatory. “This allows us to trust the interpretation of our observations, including the estimation of the mass of the black hole.”
The EHT observations use a technique called Very-Long-Baseline Interferometry (VLBI) that synchronizes telescopes located in facilities around the world and exploits the rotation of our planet to form a huge telescope the size of the Earth, observing at a wavelength of 1.3 mm. VLBI allows the EHT to achieve an angular resolution of 20 microseconds of arc (enough to read a newspaper in New York from a cafe in Paris).
Why have we never seen a black hole?
For years, the Event Horizon telescope has been looking into the heart of the Milky Way, trying to get a picture of the location of Sagittarius A *, the central supermassive black hole in our galaxy; and in a galaxy called Messier 87, 50 million light years away from Earth, trying to visualize its black hole as well. However, black holes are literally invisible: they absorb all electromagnetic radiation, which means that none of our telescopes (radio, X-rays, optics, gamma rays) can detect them. Hence we have never seen one. Up to now.
We have spoken with the Valencian astronomer Amadeo Aznar from the APT Observatory Group about this great astronomical milestone:
What is this challenge of photographing a black hole comparable to?
“The great discoveries in astronomy have been preceded by theories that supported those findings. Important discoveries have been made in the last century; one of the most prominent was the detection of the Higgs boson in 2012. This was a feat for science. CERN researchers had detected the particle that gave mass to all the others, the God particle. This discovery confirmed the postulate of the Standard Model of Particle Physics, which explains how mass originates. The existence of this particle was already predicted fifty years earlier ”.
“Saving the scales of time and size, and from the historical point of view, the capture of the event horizon can be similar to the feat of our ancestors when they detected in 1801 the first asteroid, Ceres. At that time, it was known that an object should exist between the orbit of Mars and Jupiter, thanks to the Titius-Bode Law. The existence of this object was known by indirect methods. There must have been some massive object causing alterations in the orbits of other planets, but it had never been directly observed. This object was not directly observed until years later. This was a milestone in 19th century astronomy. Now history repeats itself, albeit on a larger scale ”, continues Aznar.
“In the case of black holes, we have known about their existence for a century thanks to Albert Einstein’s Law of Relativity, and we also have an idea of their structure, but we have never observed one directly. Once again the theoretical methods have anticipated a scenario that today we have the possibility to contemplate ”, clarifies the expert.
What impact do you think the images presented by the global Event Horizon Telescope consortium will have?
“ Its repercussion will undoubtedly be far-reaching. On the one hand, data is being generated that will take years to process, and therefore to assimilate. On the other hand, the information we obtain will reveal a reality that could be different from that of the models with which we are currently working. Many of these models are based on simulations performed by supercomputers. These simulations will have to be enriched with the information that we will obtain during the next years ”.
Why would seeing the event horizon put Relativity to the test?
“The event horizon corresponds to the first rays of light that black holes let out. Right on that frontier, the laws of gravity meet the laws of quantum physics. Analyzing this limit is crucial to understand how both laws coexist in this dimension. Today we have not yet found the missing link that unifies both laws ”, concludes Aznar.
We bid farewell with a quote from the project manager, Sheperd S. Doeleman “We have achieved something that, just a generation ago, seemed impossible. Revolutionary advances in technology, connections between the world’s best radio wave observatories, and innovative algorithms, all put together, have opened a totally new window for the study of black holes and the event horizon. “
Image credit: EHT
