Here’s a very interesting question: What exactly is at the center of our galaxy? Is there a black hole ? How do we go about studying it?
A group of researchers from UCLA’s Galactic center group were inspired by the same question and decided to look at a region in the sky where they believed was the center of our milky way galaxy.
And this is what they found of the trajectories of stars surrounding the proposed center of the galaxy:
The star in the middle is the proposed center of our galaxy.These images were taken through the years 1996 – 2016 (see top right of gif).
The first thing that you notice about these stars is that they are orbiting a point in space. This is very similar of how planets in our solar system are orbiting the sun.
One of the special stars in that animation is S0-2 which completes its elliptical orbit in only 15 years!
( it takes the sun approximately 225-250 million years to complete one journey around the galaxy’s center )
But having this knowledge of how small the orbit is, we can use Kepler’s law to find out the Mass at the center of the galaxy:
And we get the mass of the center as a staggering 4 million times the mass of the Sun.
Let’s take a look at the orbits once again:
The radius of this object at the center, in order to avoid collision with the rest of the objects has to be about the diameter of Uranus’s orbit.
So, an object that has 4 million times the mass of the Sun. and diameter of Uranus’s orbit .. Hmm.. The only astronomical object that would fit this characteristic is a Super Massive Black Hole (SMBH)
And that’s why we believe that at the center of our galaxy is a SMBH.
Hope you guys liked this post. Have a good one!
* This is how the actual data of the stars orbiting this apparent black hole looks like:
**(Lecture) Dr. Andrea M. Ghez “The Monster at the Heart of Our Galaxy”
*** (TED Talk) Andrea Ghez: The hunt for a supermassive black hole
All images/animations featured in this post were created by Prof. Andrea Ghez and her
research team at UCLA and are from data sets obtained with the W. M.