HOW COME IS THERE A BLACK HOLE IN OUR GALAXY?
In the center of our galaxy the Milky Way, there is a region that demands the velocity of a particle to escape from its gravitational influence (the escape velocity) to be faster than the speed of light. The region is called the black hole.
The question is, why is there a black hole in the center of the Milky Way. The answer is pretty simple: Based on the Theory of Relativity, there is a prediction, that there is a black hole at the core of every galaxy. But in order to really understand why, scientists need more knowledge than we currently possess. We don't even have enough data and observations to prove it. It was the year 2018 when the black hole inside the Milky Way was confirmed based on the observation of the objects close to it, yet we do not have an image of it yet. We have just gotten the first image ever of the black hole, this one in the galaxy M87, a few weeks ago (April 2019), and we need to go on from here.
BALCK HOLE IN THE MILKY WAY COMPARED TO THE BLACK HOLE ON THE FIRST IMAGE
There are more black holes inside one galaxy, also inside our galaxy. But in this blog, we are going to focus on the two lying in the center. The one being in the center of our galaxy is named Sagittarius A* and the other on the famous first image is named M87* and lies in the center of the galaxy M87.
Before we come to a comparison, let us explain the so often heard lightyears. A lightyear is a distance that light travels in a vacuum in one year. In kilometers that would mean 1 lightyear = 9,5 trillion kilometers.
WHY DIDN´T WE TAKE AN IMAGE OF THE BLACK HOLE CLOSER TO US?
This is a very logical question to ask.
In April 2017 both black holes, M87’s and Sagittarius A*, were observed simultaneously and radio images of the both were taken. The team of scientists then decided to first try the luck with M87*. They had two good reasons.
The first reason is, that just because something is closer, it is not necessarily easier to track. If the object is more distant, it means it is from our perspective more stable. Meaning, the black hole inside Messier 87 was a better option to take an image of, precisely because it is so far away.
The second reason is, that there are billions of stars, planets, different celestial objects and dust floating in the same flat disk of our galaxy the Milky Way, making the black hole hard to see from the Earth´s perspective. It is the position itself that matters, not only the distance. And M87* proved a better option.
The black holes remain one of the most interesting objects inside our universe.