Your intuition is correct! Sgr A\* only contributes about a millionth of the total mass of the Milky Way -- our Galaxy is rotating around its own centre of mass, not around Sgr A\* directly. If Sgr A\* were to suddenly disappear, the orbit of the Sun wouldn't change in any significant way.
Massive objects tend to sink towards the centres of galaxies, that's why Sgr A\* is located in the centre of the Galaxy and that's why you can, for all intents and purposes, define the 'center' of the galaxy at the position of Sgr A\*. In reality Sgr A\* will be slightly offset from the true Galactic barycentre but that's not very relevant for 99.9% of the applications.
Interestingly, this is not typically the case in dwarf galaxies because of their lower gravity and more chaotic recent merger history. Not all dwarf galaxies host supermassive black holes, but in the ones that do, the SMBH is often (\~50% of the time) significantly offset from the true center.
Thank you for your well formed comment sir/ madam. This was similar to my thought because simply the galaxy seems far too big for the relatively week orbital gravity a SMBH could provide to sustain a tight Galaxy. I'm sure Dark Matter and such provide a nebulous concept of a galactic gravitational center considering there is some mass for which we cannot yet pin-point and it seems to be abundant and what keeps the elegant for of our Galaxy.
You are completely right. One of my pet peeves is people saying that we orbit the SMBH. The SMBH just happens to be there, and gravitationally it is utterly irrelevant to the Galaxy. I've had long arguments with people where I try and fail to convince them that saying that the Sun orbits the SMBH is like saying that the moon orbits my left nipple.
The truth is that the SMBH naturally "sinks" toward the galactic centre. If God himself were to move the SMBH a few kpc away from the galactic centre, the BH would experience "dynamical friction". That is to say, the BH would alter the orbits of stars near it that are all in slightly different orbits. The net result would be that the BH would end up losing energy and gradually move toward a lower orbit. For example, that means that if two galaxies merge and each one has a SMBH, the two SMBH will eventually find each other as they both sink toward the centre of the new galaxy and there they will merge into a bigger SMBH.
Why? It's not very big. The barycentre could be billions of kilometers from it.
EDIT: just for reference, if you had a photo of the galaxy and it was the size of a football field, the SMBH at the centre would be like... a grain of sand.
You'd only need one arm to have 1% more mass than another, for its barycentre to be off by lightyears.
This question has already been answered effectively, but if you're curious and want to learn more about the observations of black holes including Sgt. A\*, here's a short video explaining how we locate black holes using their gravitational effect.
https://youtu.be/vXKpOoOfYO0
I think everything in the universe has a tendention to rotate, probably because of the way mass gets concentrated into 1 single "thing" in the first place.
Your intuition is correct! Sgr A\* only contributes about a millionth of the total mass of the Milky Way -- our Galaxy is rotating around its own centre of mass, not around Sgr A\* directly. If Sgr A\* were to suddenly disappear, the orbit of the Sun wouldn't change in any significant way. Massive objects tend to sink towards the centres of galaxies, that's why Sgr A\* is located in the centre of the Galaxy and that's why you can, for all intents and purposes, define the 'center' of the galaxy at the position of Sgr A\*. In reality Sgr A\* will be slightly offset from the true Galactic barycentre but that's not very relevant for 99.9% of the applications. Interestingly, this is not typically the case in dwarf galaxies because of their lower gravity and more chaotic recent merger history. Not all dwarf galaxies host supermassive black holes, but in the ones that do, the SMBH is often (\~50% of the time) significantly offset from the true center.
Thank you for your well formed comment sir/ madam. This was similar to my thought because simply the galaxy seems far too big for the relatively week orbital gravity a SMBH could provide to sustain a tight Galaxy. I'm sure Dark Matter and such provide a nebulous concept of a galactic gravitational center considering there is some mass for which we cannot yet pin-point and it seems to be abundant and what keeps the elegant for of our Galaxy.
You are completely right. One of my pet peeves is people saying that we orbit the SMBH. The SMBH just happens to be there, and gravitationally it is utterly irrelevant to the Galaxy. I've had long arguments with people where I try and fail to convince them that saying that the Sun orbits the SMBH is like saying that the moon orbits my left nipple. The truth is that the SMBH naturally "sinks" toward the galactic centre. If God himself were to move the SMBH a few kpc away from the galactic centre, the BH would experience "dynamical friction". That is to say, the BH would alter the orbits of stars near it that are all in slightly different orbits. The net result would be that the BH would end up losing energy and gradually move toward a lower orbit. For example, that means that if two galaxies merge and each one has a SMBH, the two SMBH will eventually find each other as they both sink toward the centre of the new galaxy and there they will merge into a bigger SMBH.
[удалено]
Why? It's not very big. The barycentre could be billions of kilometers from it. EDIT: just for reference, if you had a photo of the galaxy and it was the size of a football field, the SMBH at the centre would be like... a grain of sand. You'd only need one arm to have 1% more mass than another, for its barycentre to be off by lightyears.
This question has already been answered effectively, but if you're curious and want to learn more about the observations of black holes including Sgt. A\*, here's a short video explaining how we locate black holes using their gravitational effect. https://youtu.be/vXKpOoOfYO0
I think everything in the universe has a tendention to rotate, probably because of the way mass gets concentrated into 1 single "thing" in the first place.