For the first time, astronomers have captured an image of the supermassive black hole, or SMBH, at the center of our galaxy. It is the first direct observation confirming the presence of the black hole known as Sagittarius A* (pronounced A-star) as the heart of the Milky Way.
Black holes don’t emit light, but the image shows the black hole’s shadow surrounded by a bright ring, which is actually light bent by the black hole’s gravity. Astronomers said the black hole is 4 million times more massive than our sun and is setting the supermassive category. So what exactly are supermassive black holes?
Black holes fall into 4 basic categories: stellar, intermediate, supermassive, and miniature black holes. Of these, only intermediate and miniature black holes have been hypothesized.
As stars reach the end of their lives, they tend to swell, lose mass, and then suddenly cool to form white dwarfs. A stellar black hole is formed when a giant star burns all of its fuel and collapses. These stars are often more than 10-20 times larger than our sun.
Stellar black holes grow by taking control of other stars or merging with other black holes and becoming a supermassive black hole. Basically when a black hole consumes multiple stars or many smaller black holes. As mentioned earlier, a stellar black hole has a mass about 10 to 20 times that of our Sun. A supermassive black hole can have masses in the billions of suns, so the one at the center of the Milky Way is quite small.
Supermassive black holes are usually found at the center of a galaxy. It is postulated that most galaxies have at least one supermassive black hole at their center. If there is more than one supermassive black hole, they are likely to collapse into each other, forming a larger supermassive black hole.
Regardless of their initial size, Black holes can grow throughout their livesslurps gas and dust from any objects that crawl too close, making it virtually impossible to determine the exact mass of any given supermassive black hole.
Although humans cannot see black holes even with the best and most powerful telescopes, we can observe a black hole’s effect on light rays. When normal stars are sucked in by black holes, they accelerate and heat up, emitting X-rays that are detected by X-ray-capable space telescopes. That’s how we ended up photographing Sagittarius A* or any other black hole.
Since it is established that almost all galaxies have at least one supermassive black hole, it is established that there must be at least 100 billion supermassive black holes in our corner of the universe alone. Of those billions, we have only been able to directly image two, including the Milky Way’s Sagittarius A*.
The first was the black hole at the center of the giant elliptical galaxy Messier 87an SMBH with a mass at least 1000 times greater than Sagittarius A*.
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