Today, astronomers revealed a picture taken for the first time of a giant black hole centered in the center of our galaxy known as the Milky Way.
The black hole, called Sagittarius-A-star, is four million times the size of the Sun.
What we see in the image is a central black region in which the hole sits, surrounded by light from very hot gas, which is accelerated by the massive gravitational forces.
To approximate the picture in terms of size, the ring of light surrounding the hole is about the size of Mercury’s orbit around the sun.
The orbit is approximately 60 million kilometers, or 40 million miles, in diameter.
Fortunately, this “monster” is a very long distance from us – about 26,000 light-years, so there is absolutely no possibility of any danger to us from it.
The image is the result of the work of an international team called the Event Horizon Telescope Collaboration, known for its acronym EHT.
And this is the second photo of them after they published in 2019 a picture of a giant black hole in the heart of another galaxy called Messier 87 or M87. And that hole was a thousand times larger than this, as it was about 6.5 billion times larger than the size of the Sun.
What is a black hole?
- A black hole is a region of space in which matter has eaten away
- Gravity is so strong that nothing, not even light, can escape it
- Black holes appear from the demise of certain large stars by explosion
- But some of them are very massive and are billions of times larger than the size of the Sun
- It is not known how these giant holes, which were found in the middle of galaxies, were formed
- But it is clear that it revitalizes the galaxy and will affect its evolution
The image is the product of a major technical advance.
At a distance of 26,000 light-years from Earth, the black hole “Sagittarius-A-Star” appears like a tiny needle-prick in the sky. In order to distinguish such a target, very high accuracy was required.
The method that achieved this goal for the telescope is a technique called “Very Long Basic Array interferometry”.
This technology basically consists of connecting a network of eight wide-area wireless antennas in order to mimic the work of an Earth-sized telescope.
This arrangement allows the telescope to cut an angle in the sky measured in micro-arcseconds. Telescope team members talk about the visibility of something close to being able to see a loaf of bagel on the moon.
And even after that happens, atomic hours, smart algorithms, and countless hours of supercomputing are needed to build an image out of petabytes (one petabyte is one million gigabytes) of collected data.
The way a black hole bends light means that there is nothing to see but a “shadow”, but the brilliance of the material that surrounds this darkness and spreads out in a circle known as the accretion disk, does not indicate where the hole is.
And if you compare the new image to the previous image of M87, you might wonder what the difference is between them. But there are basic differences between them.
“Because the Sagittarius-A-star hole is much smaller than the previous black hole – about a thousand times smaller – its ring composition changes on timescales a thousand times faster,” explains team member Ziri Younesi from University College London in the UK. Very mobile. The hot spots you see in the loop are moving around from day to day.”
This is very clear from the team’s simulations of what you would see if you could somehow get to the center of our galaxy and see the scene with radiofrequency-sensitive eyes.
Very hot gas, or plasma, travels in the ring around the black hole at a speed equal to a large fraction of the speed of light (300,000 kilometers per second or about 190,000 miles per second). And the bright regions are most likely the places where matter is spinning towards us and where light emissions are activated or enhanced as a result.
These rapid changes in the vicinity of the Sagittarius-A-star black hole are one of the reasons why the image production took longer than that of the M87 black hole. Interpreting the data was a tougher challenge.
In fact, telescope observations of black holes were obtained during the same period in early 2017, but the black hole “M87”, with its largest size and its distance of 55 million light-years, appears static compared to the second hole.
Scientists are beginning to use the measurements in the new image to test the physics we currently use to describe black holes. So far, what they’re seeing is perfectly in line with the equations Einstein put into his theory of gravity and relativity.
For decades, we suspected that there was a supermassive black hole at the heart of the galaxy. Otherwise, what produces attractive forces that accelerate neighboring stars through space, making them travel at a speed of up to 24 thousand kilometers per second (in comparison, our sun travels around the galaxy at a speed of 230 kilometers per second).
But, interestingly enough, when the Nobel Prize Committee honored astronomers Reinhard Genzel and Andrea Geis with its physics prize in 2020 for their work on the Sagittarius-A-star black hole, the mention was only of a “huge chunky object.” This was a way of evading in the event that another strange phenomenon might be the explanation.
But now there is no longer room for doubt that things are clear.
Starting in August, the new massive space telescope, James Webb, will shift its lenses to the Sagittarius-A star black hole. The $10 billion telescope will not be accurate enough to take a direct image of the black hole and its accretion ring, but it will bring a new possibility to study the environment around the black hole through its very sensitive infrared instruments.
Astronomers will study in unprecedented detail the behavior and physical nature of hundreds of stars orbiting the black hole. They will even look for the possibility of star-sized black holes in the region, and for any evidence of a concentrated clump of invisible or black matter.
“Every time we get a new facility that can take a clearer picture of the universe, we do our best training it at the center of the galaxy, and we end up learning something amazing,” said Professor Jessica Lu, from the University of California, Berkeley, in the US, who will lead the Webb campaign. “.
The findings of the EHT collaboration team will be published in a special issue of The Astrophysical Journal Letters.