Do stars in our Milky Way really orbit around a super massive black hole ?

[mariuslvasile]

Many if not all youtube cosmoillogists claim that all stars from galaxies like our Milky Way are orbiting around a super massive black hole which lies in its center. Like most things astromorons say, that is simply not true. The stars orbit their shared center of mass, or barycenter. Here is why:

Marius: Do galaxies have a barycenter ?

Yes, galaxies have a barycenter, which is the center of mass for the entire system.

Individual Galaxy Barycenters

The Galactic Center: For a single galaxy like the Milky Way, the barycenter is the point around which all its stars, gas, and dark matter rotate.

Location: This point is usually located in the galactic bulge, near a supermassive black hole (like Sagittarius A* in our galaxy).

Misconception: Contrary to popular belief, stars do not "orbit the black hole" in the same way planets orbit the Sun. The black hole’s mass is only a tiny fraction (about 0.000003%) of the galaxy's total mass. Instead, both the black hole and the stars orbit the galaxy’s shared center of mass.

Larger Scale Barycenters
Galaxies also exist in groups that share common centers of mass:

Galaxy Groups: Our Milky Way and the Andromeda Galaxy are part of the Local Group. They are currently moving toward a shared barycenter located somewhere between them.

Galaxy Clusters: Larger collections of galaxies also orbit a common barycenter, often dominated by vast amounts of dark matter and hot plasma.



Marius: So galaxies spin around their center of mass/barycenter no matter if there is a black hole there or not

Correct. Galaxies rotate around their barycenter (center of mass) regardless of whether a supermassive black hole is present.
While supermassive black holes (SMBHs) are often found at the exact centers of galaxies, they are not the "anchors" that cause the galaxy to spin.

Key Facts About Galactic Rotation

The Black Hole's Mass is Negligible: A typical SMBH makes up only about 0.001% (or even less) of a galaxy's total mass. If the Milky Way’s central black hole were suddenly removed, the rest of the galaxy would continue rotating essentially unchanged.

Self-Gravity and Dark Matter: A galaxy is held together by the combined gravity of its billions of stars, massive gas clouds, and, most significantly, a massive "halo" of dark matter. This collective mass defines the barycenter and dictates the rotational behavior.

Galaxies Without Black Holes: Astronomers have identified some galaxies, such as M33 (the Triangulum Galaxy), that appear to have no central supermassive black hole at all. These galaxies still rotate around their barycenters normally.

Why the Black Hole is There: SMBHs migrate to the center of mass because of dynamical friction. As they move through the galaxy, they interact with hundreds of thousands of stars, losing energy and naturally "sinking" to the gravitational center over billions of years.

Independent Spin: The spin of a central black hole is often not aligned with the rotation of the galaxy itself. This indicates that the black hole's own rotation is governed by the specific material it recently "ate" rather than the overall spin of the galaxy.

In short, a galaxy spins because of the conservation of angular momentum from the original cloud of gas and dust that formed it—the black hole is just a relatively small passenger at the center.

So people who claim this are just plain astromorons who dont understand basic astrophysics. There is no need for any super massive black hole to explain why stars orbit a central point in the galaxy.

[crawler]

Singularity black holes do not exist.
But i am ok with supermassive black (or brown) stars (or bodies).

Az u are aware, my centrifuging of aether idea means that galaxies etc do not orbit a barycenter, their gravity orbits are affected by the faux gravity caused by spinning or orbiting bodies, especially by the spinning, especially by so-called black holes.

[mariuslvasile]

That's the point, they don't exist, and they think they exist because they see stars orbiting that central point. But there really isnt anything in that point (except aether), it's just the centre of mass of the galaxy, so everything rotates around it.
What's funny is that even Einstein claimed that black holes dont exist, and that singularities are impossible to exist. And he used the same GR theory that others used to prove they exist. This is not the first time when GR gave opposite results for different people, as it resulted in a contracting universe for Einstein and an expanding universe for Friedmann.

I wasnt aware of your theory, but it sounds like a full aether drag theory to me (Stokes theory), where the aether is moving along with the stars/planets. But this makes aether wind zero relative to them, so you need to decide which aether model you are assuming to be correct: stationary or fully dragged. You can't just assume both at the same time. Or maybe you go for the middle way where its partially dragged ? But then you said Fresnel was wrong and aether is not dragged, but photons, so it cant be that.

[mariuslvasile]

A simple example to illustrate how this works is by using a binary star system where both stars have equal mass. The stars will not orbit around each other, but around their common center of mass, which is situated at half the distance between their centers of mass. But there is nothing special or supranatural going on in that point, no singularity, no unicorns, and no voodoo magic either.

Yes, in a binary system with two stars of equal mass, both stars will orbit around a common center of mass (barycenter) located exactly at the midpoint, or one-half of the distance, between their centers. Due to their equal gravitational pull, they move in identical elliptical (or circular) orbits on opposite sides of this central point. 

Key details regarding this system: 

Center of Mass: For equal masses (m1=m2), the center of mass is equidistant from both stars (d1=d2=dtotal/2).

Orbital Motion: Both stars move in their orbits with the same angular velocity, ensuring they remain diametrically opposite each other at all times.

Orbit Shape: They orbit their common barycenter, which is a key characteristic of binary systems. 

 

In a binary system with two stars of equal mass, both stars orbit around their common center of mass, which is located exactly midway between their centers.

Center of Mass in Equal-Mass Binary Systems

For a system of two bodies with equal mass m1=m2, the center of mass (COM) is calculated as:

RCOM=(m1r1+m2r2)/(m1+m2)


If the stars are separated by a distance d, and their masses are equal, the COM lies exactly at the midpoint, i.e., at a distance d/2 from each star.

Orbital Motion

Both stars orbit the common COM, not each other.

Since they have identical masses, their orbits are mirror images, and they each follow a circular or elliptical path around the COM, with the COM remaining stationary at the midpoint (in an inertial frame where no external forces act).

The orbits are synchronized in period but opposite in direction, maintaining the COM stationary.

Key Implications

The statement in the query is correct: the point around which both stars orbit is situated half the distance between their centers, i.e., the center of mass.

If one star were more massive than the other, the COM would shift toward the more massive star, and the stars’ orbits would have radii inversely proportional to their masses.

Summary

In an equal-mass binary star system:

Each star traces an orbit around the midpoint of their separation.

The orbital radius for each is exactly half the separation.

The COM remains stationary (neglecting external forces), and the system exhibits perfect symmetry.

This principle is fundamental in stellar dynamics and observational astronomy, such as when determining binary  star masses from orbital periods and separations

And the same principle applies to star systems made of more than 2 stars, like ternary star systems:

In a ternary system with three stars of equal mass, the calculation of the center of mass (COM) generalizes naturally from the binary case while preserving the concept of a mass-weighted average position. Consider three stars, each of mass mm, located at positions r1​, r2​, and r3​ in a three-dimensional space. The center of mass is given by the vector formula:

RCOM=mr1+mr2+mr3/m+m+m=(r1+r2+r3)/3

Properties for Equal-Mass Stars:

Equidistant Balance: If the stars are positioned symmetrically (e.g., at the vertices of an equilateral triangle), the COM lies at the geometric center of the triangle. More generally, the COM is simply the arithmetic mean of the three positions.

Vector Distances from COM: Define vectors from the COM to each star:

ri COM=ri−RCOM,i=1,2,3

These vectors satisfy the zero vector sum condition due to equal 
masses:

r1 COM+r2 COM+r3 COM=0

This is the ternary analog of the binary relation r1+r2=0 (with appropriate vectors) for the equal-mass two-body system.

Orbital Considerations: If the stars orbit each other under mutual gravity, their motion can be described in the COM frame such that vectors from the COM trace paths determined by their initial positions and velocities, preserving the COM at rest in an inertial frame.

Summary:

For three stars of equal mass, the center of mass is the arithmetic mean of their positions:

RCOM=(r1+r2+r3)/3

The relative positions of the stars with respect to the COM satisfy a vector sum of zero:

∑i=13(ri−RCOM)=0.i=1∑3​(ri​−RCOM​)=0.

This ensures the COM remains stationary in an inertial frame, while each star orbits or moves relative to the COM depending on the system's dynamics.

For symmetric layouts (equilateral triangle, linear arrangement with equal spacing), the COM coincides with the geometric center of the configuration.

This vector-based approach generalizes straightforwardly to N-body systems as well: the COM is always the mass-weighted average of positions, and for equal masses, it reduces to the simple arithmetic mean.

ucf.edu

18.2 Measuring Stellar Masses – Astronomy

[crawler]

That's the point, they don't exist, and they think they exist because they see stars orbiting that central point. But there really isnt anything in that point (except aether), it's just the centre of mass of the galaxy, so everything rotates around it.
What's funny is that even Einstein claimed that black holes dont exist, and that singularities are impossible to exist. And he used the same GR theory that others used to prove they exist. This is not the first time when GR gave opposite results for different people, as it resulted in a contracting universe for Einstein and an expanding universe for Friedmann.

I wasnt aware of your theory, but it sounds like a full aether drag theory to me (Stokes theory), where the aether is moving along with the stars/planets. But this makes aether wind zero relative to them, so you need to decide which aether model you are assuming to be correct: stationary or fully dragged. You can't just assume both at the same time. Or maybe you go for the middle way where its partially dragged ? But then you said Fresnel was wrong and aether is not dragged, but photons, so it cant be that.

My centrifuging of aether theory is based on the aether theory that aether accelerating into mass (eg Earth)(where aether is annihilated) accelerates objects with it (which givs us gravitational mass).
Which is itself based on aether theory that an object with uniform velocity duznt drag aether.
And that an accelerating object needs to drag aether with it (which givs us inertia & inertial mass).
And imo the dragged aether drags objects from the nearby cosmos, thusly giving the inertia, no cosmos means no inertia (Mach was correct).
So, my centrifuging of aether theory is the other side of that coin.
The acceleration of spin or orbit must drag aether, ie aether is sucked in at a spinning object's equator -- in which case aether must be spat out at the object's 2 poles (unless aether is annihilated which it is not)(& unless aether self dissipates, which i reckon it duz not)(ie i don not agree with some aetherists that aether is contractile).
So, imo there is a circulation of aether, in at equator, out at poles.
So, imo there is an acceleration into say Earth (an accn of aether, & an accn of objects), in at equator, & allso in at the poles.
So, imo there is a faux gravity, due to spin (& allso due to orbit). In addition to ordinary gravity.