Ever dream of seeing an invisible object? Twenty-seven thousand light-years away from Earth, there is a supermassive black hole that you will find at the center of the Milky Way galaxy.
‘Sagittarius A’ is the massive cosmic photographed in space by an international team of astronomers, Event Horizon Telescope (EHT); it was released three years after the first image of a black hole from a distant galaxy.
“It’s very exciting to show you today this best-ever image of Sagittarius A.”
EHT project director Huib van Langevelde.
Black holes are regions of space where the pull of gravity is so intense that nothing can escape, including light. If you jumped into a stellar-mass black hole, your body would be subjected to a process called ‘spaghettification.’ The black hole’s gravity force would compress you from top to toe while stretching you at the same time, sounds like you would be a pasta just like the food you eat at a restaurant.
If you see the image that looks like a ring of fire, it does not define the black hole itself since it is fully dark, but the shining gas represents radio waves being given off by material swirling around the black hole.
“These unprecedented observations have greatly improved our understanding of what happens at the very centre of our galaxy.”
aid EHT project scientist Geoffrey Bower, of Taiwan’s Academia Sinica.
In a statement provided by the French National Centre for Scientific Research (CNRS), Bower also said that the observations had offered “new insights on how these giant black holes interact with their surroundings”.
The results are published in The Astrophysical Journal Letters.
VIRTUAL TELESCOPE
Sagittarius A, owes its name to its detection in the direction of the constellation Sagittarius. Its existence has been assumed since 1974, after detecting an unusual radio source at the centre of the galaxy.
In the 1990s, astronomers mapped the orbits of the brightest stars near the centre of the Milky Way, confirming the presence of a supermassive compact object there, work that led to the 2020 Nobel Prize in Physics.
Though the presence of a black hole was thought to be the only plausible explanation, the new image provides the first direct visual proof.
Because it is 27,000 light-years from Earth, it appears the same size in the sky as a donut on the Moon.
Capturing images of such a distant object required linking eight giant radio observatories across the planet to form a single “Earth-sized” virtual telescope called the EHT. These included the Institute for Millimeter Radio Astronomy (IRAM) 30-meter telescope in Spain, the most sensitive single antenna in the EHT network.
The EHT gazed at Sgr A* across multiple nights for many hours in a row, a similar idea to long-exposure photography and the same process used to produce the first image of a black hole, released in 2019.
That black hole is called M87* because it is in the Messier 87 galaxy.
MOVING TARGET
The two black holes bear striking similarities, although Sgr A* is 2,000 times smaller than M87*.
“Close to the edge of these black holes, they look amazingly similar.”
era Markoff, co-chair of the EHT Science Council, and a professor at the University of Amsterdam.
Both behaved as predicted by Einstein’s 1915 theory of General Relativity, which holds that the force of gravity results from the curvature of space and time, and cosmic objects change this geometry.
Although Sgr A* is much closer to us, imaging it presented unique challenges. Gas in the vicinity of both black holes moves at the same speed, close to the speed of light. But while it took days and weeks to orbit the larger M87*, it completed rounds of Sgr A* in just minutes.
The brightness and pattern of the gas around Sgr A* changed rapidly as the team observed it, “a bit like trying to take a clear picture of a puppy quickly chasing its tail,” said EHT scientist Chi-kwan Chan of the University of Arizona.
The researchers had to develop complex new tools to account for the moving targets. The resulting image — the work of more than 300 researchers across 80 countries over five years — is an average of multiple images that revealed the invisible monster lurking at the centre of the galaxy.
Scientists are now eager to compare the two black holes to test theories about how gasses behave around them, a poorly understood phenomenon thought to play a role in forming new stars and galaxies.
Probing black holes- particularly their infinitely small and dense centers known as singularities, where Einstein’s equations break down- could help physicists deepen their understanding of gravity and develop a more advanced theory.