Black Hole Science: How Do Scientists Know The Center Of The Milky Way Galaxy Has A Black Hole?
A black hole is perhaps the most fascinating object in existence. Astronomers suspect that black holes are closely tied to the structure and formation of galaxies. In fact, it’s thought that an enormous black hole exists at the center of our own Milky Way galaxy, influencing its size and growth. It should be noted that these particular black holes at the heart of galaxies are millions or even billions of times larger than the average black hole.
— Chandra Observatory (@chandraxray) May 4, 2017
But how can scientists be certain that this is the case in our galaxy, particularly given the fact that black holes can’t be directly observed because of their massive gravitational pull that draws in even light. Black holes are – hopefully – all many thousands of light years away and not really accessible to us. And even if one was close by that we could study, it probably wouldn’t be the safest activity imaginable.
So how do they know for sure there’s one in the Milky Way core? As noted by Science Daily, the answer is that these scientists detect a black hole by the effect it has on its surrounding environment.
For example, some researchers have studied the ways that groups of stars near the center of the Milky Way behave and orbit. In order to detect and record these orbits, scientists first had to focus on the red part of the spectrum so that they could see through the thick dust and clouds near the center of the galaxy.
In this way, they saw that a number of stars at the core were orbiting around something invisible that emitted no light of its own. This strongly suggests a massive black hole, but was not sufficient evidence in itself to prove a galactic black hole.
The next step then was to roughly measure the size of the object by the ellipses of the stars orbiting it. In other words, if something is orbiting outside of the object, the object is naturally smaller than that. After this, it was a simple calculation using Kepler’s laws of motion to determine the mass of the unseen object. Based on these calculations, it’s been determined that this invisible object at the center of the Milky Way has a mass four million times that of the sun and is roughly six light hours in diameter.
This estimated size is more or less equivalent to the orbit of Uranus around our sun. Given the incredible mass indicated and the relatively small size, this huge object has to be an enormous black hole. It really couldn’t be anything else.
From a logical standpoint, it only makes sense that if there is a supermassive black hole at the center of our own Milky Way galaxy, then this is probably the case – or at least could be the case – for other galaxies as well. It may be that such supermassive black holes serve as the gravitational seed around which gas and dust form to create new galaxies filled with billions of stars.
After all, we already know that the slow accumulation of matter – gas, dust, and cometary materials – help to form our own solar system, including not only the sun, but the planets as well. This same process would allow relatively small black holes to gradually become gargantuan monsters that eat the centers of galaxies.
Of course, this would also seem to suggest that the neighborhood surrounding the center of our galaxy would be an extremely unpleasant and hazardous place for any life forms or civilizations that might come into being there – assuming that was even possible. As noted by Popular Mechanics, a black hole gives off an enormous amount of radiation from its constant consumption of surrounding matter, which in itself would be a dangerous situation for any nearby civilization. And of course, there’s always the possibility of being sucked into oblivion.
[Featured Image by NASA/CXC/MIT/F.K.Baganoff/Getty Images]