Astronomers who attempt to capture the first images of the black hole in the heart of the Milky Way have made it clear that the ambitious project was successful.
The observations, by the Horizon Telescope of the event, should be unveiled in spring in one of the most anticipated scientific announcements of 2019. Now, a senior scientist of the project said that "spectacular" data are been collected during the observations of two black holes, including Sagittarius A * in the center of our galaxy.
"We have been able to get very high quality data at the very high resolutions necessary to observe the shadow [black hole’s] if it is really there," said Sera Markoff, professor of astrophysics, theoretical and astroparticle physics at the University of Amsterdam, which co-leads the Multiwavelength Working Group of EHT.
The team is in the final phase of reviewing the data collected in 201
Prof Peter Galison, who is based at Harvard University's Department of History of Science and is also involved in the project, claimed that, if successful, the EHT would first image become one of the most significant in the last 50 years of astronomy. "If we get an image, it will become one of the iconic images of science," he said. "It's an extraordinarily ambitious project."
There are few doubts about the existence of black holes: the phenomenally dense objects distort the plot of space-time in their vicinity, causing objects and light to seem to steer off course. More recently, the Ligo gravitational wave observer has detected ripples emitted in space-time when pairs of black holes collide.
Until now, however, a black hole has never been directly observed. The main barrier is that the black holes are so compact that a telescope the size of the Earth would be needed to see even the closest.
The EHT bypasses this link by connecting 15-20 telescopes on the South Pole, Europe, South America, Africa, North America, and Australia. Collectively, the array has a resolution equivalent to that of being able to see a thumbtack in New York from London.
The EHT uses a technique known as interferometry, in which observer astronomers from different continents simultaneously observe the same object, and then combine the data collected on a supercomputer.
This requires that all the telescopes of the array rotate towards the target black hole and measure each radio wave coming from its direction. Coordinating this was a "huge result of diplomacy and organization", according to Galison.
The EHT has two primary objectives: the Sagittarius A *, at the center of the Milky Way, and a supermassive black hole called the M87 in the Virgo group of galaxies. M87 is about 50m-60m light years away, but at more than six billion solar masses (1000 times larger than our local black hole), astronomers hope it should be visible.
No one is sure how the image will be but the theoretical predictions show a black outline, contrasted to a radiant surrounding glow, something like the representation in the film Interstellar. "You'll imagine seeing a shadow or a black depression," Markoff said.
In addition to telling us what the black holes are, EHT could also reveal if they have properties predicted by Einstein's general relativity theory and give insights on the exotic processes that occur in the extreme environment near the horizon of events.
Detailed observations will also be made on dramatic jets of material that are thrown by some black holes, including M87. It is unclear whether the Sagittarius A *, a relatively small black hole, has jets – it is possible that they are too weak to have been identified previously – and EHT could solve this question.
"We see these huge plasma jets moving almost at the speed of light," said Markoff. "It can be hundreds of millions of times the size of the black hole itself – bigger than the galaxy."
It is believed that the jets of the black hole play an important role in cosmology, contributing to the formation of the cosmic network, in which galaxies are inserted into groups through the universe.