Thursday , June 17 2021

Scientists near first black hole observation in Milky Way | Science



Astronomers trying to capture the first images of the black hole in the heart of the Milky Way gave early clues that the ambitious project was successful.

The observations, made by the Event Horizon Telescope, are due to be unveiled in the spring of one of the most anticipated scientific announcements of 2019. Now a senior scientist for the project said "spectacular" data was collected during observations of two black scientists. including Sagittarius A * in the center of our own galaxy.

"We were able to obtain high quality data at the very high resolutions necessary to observe the [black hole’s] shade if it's really there, "said Sera Markoff, professor of astrophysical and astrophysical astrophysics at the University of Amsterdam who co-leads the EHT Multiple Waves Working Group.

The team is in the final analysis phase of the data collected in 2017 and Markoff could not confirm whether the observations produced the first direct image of a black hole silhouette.

Professor Peter Galison, who works in the history of science at Harvard University and is also involved in the project, said that if it succeeds, the first image of EHT would become one of the most significant in the last 50 years of astronomy. . "If we take a picture of it, it will become one of the iconic images of science," he said. "It's an extraordinarily ambitious project."

There is little doubt about the existence of black holes: phenomenally dense objects distort the fabric of spacetime in their neighborhood, making objects and light appear to deviate from course. More recently, the Ligo gravitational observatory has detected ripples sent through spacetime when pairs of black holes collide.

So far, 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 Earth would need to see even the closest.

The EHT bypasses this by connecting 15-20 telescopes spanning the South Pole, Europe, South America, Africa, North America and Australia. Collectively, the matrix has a resolution equivalent to being able to see a drawing pin in New York from London.

The EHT uses a technique known as interferometry, in which astronomers in observatories from different continents simultaneously observe the same object and combine the data collected in a supercomputer.

This requires all the array's telescopes to rotate toward the target black hole and measure all the radio waves coming from its direction. Coordinating this was a "great achievement of diplomacy and organization," according to Galison.

The EHT has two main targets: Sagittarius A *, at the center of the Milky Way, and a supermassive black hole called M87 in the cluster of Virgo galaxies. The M87 is about 50m-60m light years, but in more than six billion solar masses (1,000 times larger than our local black hole), astronomers expect it to be visible.

No one knows for sure what the image will look like, but theoretical predictions show a black silhouette against a glow of radiation, something like the representation in the movie Interstellar. "You imagine seeing a black shadow or depression," Markoff said.

In addition to telling us how black holes look, the EHT can also reveal whether they have properties predicted by Einstein's theory of general relativity and insights into exotic processes that occur in the extreme environment near the event horizon.

Detailed observations will also be made of dramatic jets of material that are thrown out of some black holes, including the M87. It is unclear whether Sagittarius A *, a relatively small black hole, has jets – it is possible they are too weak to have been seen before – and the EHT could solve that.

"We see these huge plasma jets moving almost at the speed of light," Markoff said. "They may be hundreds of millions of times the size of the black hole itself – larger than the galaxy."

It is believed that black hole jets play an important role in cosmology, contributing to the formation of the cosmic web, in which galaxies are tied to clusters throughout the universe.


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