Unraveling the Mystery of Our Galaxy’s Black Hole
Black holes are one of the strangest and most intriguing parts of space. An international team of scientists has captured the first-ever image of the black hole found at the center of our galaxy, the Milky Way. This picture is a sight to behold, taking five years to capture and requiring the work of over 300 scientists across 80 institutes.
What Is a Black Hole?
Black holes are areas of the universe where the pull of gravity is so strong that anything close by gets pulled in. Black holes appear black as all nearbyeven light becomes trapped inside the hole and unable to escape.
Black holes form when dying stars fall in on themselves, compacting a large mass into a small area. While astronomers cannot see black holes, they can identify them by studying how they interact with nearby objects.
Thousands of potential black holes have already been discovered, but NASA predicts that there could be as many as ten million to a billion in the Milky Way alone, with many more across other galaxies. In fact, scientists believe that every large galaxy in the universe has a supermassive black hole located at its center.
How Was This New Picture Captured?
On May 12th, 2022, scientists released the first image of a supermassive black hole located at the heart of the Milky Way. This black hole was named Sagittarius A* (Sgr A*) as it is located within the Sagittarius constellation.
The stunning image was captured as part of the Event Horizon Telescope (EHT) project and was revealed at various global news conferences and published in the Astrophysical Journal Letters.
This is only the second time scientists have captured a direct image of a black hole, the first being in 2019 when they pictured a more distant one found in the galaxy M87 (this black hole was named M87*).
To capture this image, scientists combined measurements from eight large telescopes across the globe. First, each of these telescopes had to take pictures simultaneously, synchronized by a network of atomic clocks. Then, a virtual “‘super-telescope”’ the size of the Earth, was formed using the pooled data.
Scientists collected the data in April 2017 and used a supercomputer to analyze and transform it into a single image. It took several years for them to piece the information together and construct an accurate image.
While we describe this as a picture of the black hole itself, this is not strictly true. Black holes themselves are invisible. Rather, this picture shows the ring of light surrounding the black hole, known as the “event horizon,” and the dark inner shadow of the black hole itself. The “event horizon” forms as surrounding superheated gas gets sucked into the black hole.
What Does This Picture Tell Us?
Sgr A* is the closest black hole within our galaxy; located just 27,000 light-years from Earth. It has been widely studied over the years; however, this is the first time it has been imaged. By obtaining a direct image of the black hole, scientists have been able to confirm its presence, which two astronomers, Bruce Balick and Robert Brown, predicted in 1974 due to the detection of a bright radio source.
As the saying goes, “a picture paints a thousand words.” So, what does this picture tell us about our nearest black hole?
Well, it has allowed scientists to calculate the mass of Sgr A*, which is a staggering four million times heavier than the weight of the sun! However, despite its large mass, Sgr A* is small— – only thirty times wider than the sun. In fact, from Earth, the black hole would be look about the same size as a doughnut lying on the moon’s surface!
Scientists used this image to confirm Einstein’s Theory of Relativity by measuring the size of the black hole’s shadow and showing that Sgr A* is positioned face-on to Earth. In addition, by analyzing and comparing the black hole images, scientists will be better able to understand how black holes interact with the surrounding universe.
Analysis of this historic image is ongoing and may well reveal some new and exciting facts.
We can expect to see much more of Sgr A* over the coming years. EHT has continued collecting data from this black hole, and we look forward to learning more as this it is analyzed.
Moving forwards, scientists are keen to add extra telescopes across the globe to get a more detailed view of black holes across the different galaxies.
Our galaxy’s black hole is known to flare daily, increasing in brightness by up to 10 to 100 times. In 2023, EHT will work closely with the NASA Webb telescope to understand more about this phenomenon. By discovering more about the flaring nature of Sgr A*, scientists may be able to answer our big questions.
Milky Way: The spiral galaxy that contains our solar system
Supermassive: Having a very large mass (typically millions or billions of times larger than the Ssun)
Sagittarius: A defined group of stars located at a specific position in the night sky
Messier 87 or M87: A very large elliptical galaxy
Event Horizon: A distinct boundary surrounding a black hole, beyond which nothing escapes!
Einstein’s Theory of Relativity: Einstein’s theory linking space and time
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