When a massive astrophysical object, such as a boson star or black hole, rotates, it can cause the surrounding spacetime to rotate along with it due to the effect of frame dragging. In a new paper, physicists have shown that a particle with just the right properties may stand perfectly still in a rotating spacetime if it occupies a "static orbit"—a ring of points located a critical distance from the center of the rotating spacetime.
The physicists, Lucas G. Collodel, Burkhard Kleihaus, and Jutta Kunz, at the University of Oldenburg in Germany, have published a paper in which they propose the existence of static orbits in rotating spacetimes in a recent issue of Physical Review Letters.
"Our work presents with extreme simplicity a long-ignored feature of certain spacetimes that is quite counterintuitive," Collodel told Phys.org. "General relativity has been around for a bit more than a hundred years now and it never ceases to amaze, and exploring the ways that different distributions of energy can warp the geometry of spacetime in a non-trivial way is key to a deeper understanding."
In their paper, the physicists identify two criteria for a particle to remain at rest with respect to a static observer in a rotating spacetime. First, the particle's angular momentum (basically its own rotation) must have just the right value so that it perfectly cancels out the rotation due to frame dragging. Second, the particle must be located precisely in the static orbit, a ring around the center of the rotating spacetime at which the particle is neither pulled toward the center nor pushed away.
A key point is that not all astrophysical objects with rotating spacetimes have static orbits, which in the future may help researchers distinguish between different types of astrophysical objects. As the physicists explain, in order to have a static orbit, a rotating spacetime's metric (basically the function that describes spacetimes in general relativity) must have a local minimum, which corresponds to the critical distance at which the static orbit is located. In a sense, a particle may then be "trapped" at rest in this local minimum.
The physicists identify several astrophysical objects that have static orbits, including boson stars (hypothetical stars made of bosonic matter that, like black holes, have immense gravity but do not emit light), wormholes, and hairy black holes (black holes with unique properties, such as additional charge). On the other hand, Kerr black holes (thought to be the most common kind of black hole) do not have metrics with local minima, and so do not have static orbits. So evidence for a static orbit could provide a way to distinguish between Kerr black holes and some of the less common objects with static orbits.
While the physicists acknowledge that it may be unlikely to expect a particle with just the right angular momentum to exist at just the right place in order to remain at rest in a rotating spacetime, it may still be possible to detect the existence of static orbits due to what happens nearby. Particles initially at rest near the static orbits are predicted to move more slowly than those located further away. So even if researchers never observe a particle standing still, they may observe slowly moving particles in the vicinity, indicating the existence of a nearby static orbit.
"Acknowledging the existence of the static ring helps us appreciate better what to plan and expect from future observations," Collodel said. "For instance, we can search for the ring in order to identify possible exotic objects, such as the boson star, or even assure with confidence (upon observing the ring) that an AGN [active galactic nucleus] is not powered by a Kerr black hole. In the future we plan to investigate how the presence of the ring might affect accretion disks, which are at this stage much easier to observe, and if it could shield some objects from infalling matter."
Explore further:
Black holes, curved spacetime and quantum computing
More information: Lucas G. Collodel, Burkhard Kleihaus, and Jutta Kunz. "Static Orbits in Rotating Spacetimes." Physical Review Letters. DOI: 10.1103/PhysRevLett.120.201103
Also at arXiv:1711.05191 [gr-qc]
Steelwolf
Whydening Gyre
As to a planet or moonlet sitting still in it? A black hole Lagrangian point, I guess...:-)
Steelwolf
Whydening Gyre
Indeed it does appear that way, however...
Understanding that fields(gravity being the most prominent, of course, followed by magnetic, EM and so on) extend themselves at the speed of light. And have been doing so for at least the last 13.7 billion years (I'm not a big fan of BB, but nothing else fits the model at this time, so....).
With literally trillions of observed gravitational bodies to date, that's a LOT of fields scattering around and interacting ... And the aggregate combination of all those interacting fields give the appearance of a larger framework. Possible even RESULTs in a framework field we call space/time...
I find THAT a simpler explanation to dispel the need for an "aether"...
(not to mention, "dark" anything...)
thingumbobesquire
ZoeBell
May 26, 2018ZoeBell
May 26, 2018TimLong2001
ZoeBell
May 26, 2018Osiris1
I know that 97 + 04/100% will '1' this post because they do not understand it unless they are fluent in the Reynold's Equations in multivariable, multidegree partial differential coordinate equations form..... a critter from post grad fluid dynamics.
milnik
Hyperfuzzy
milnik
For you, the particles exhibit from the empty space, and since there is nothing there, then there are no particles. They are "dark" matter for you.
Hyperfuzzy
nonsense
Arginx
U just explain perfectly how dumb this idea (theory) is. THANK YOU very much. ;-)
milnik
at your conclusion, everything visible, measurable and tangible in the universe is free of particles. So there are no: protons, neutrons, electrons, and so on, it's all that nobody knows what it is. Again, you returned to BB and back, when everything went through that point, it entered another universe where everything was lent, but there were no particles. Miracle over the wonders !!
Hyperfuzzy
I do not know what you are smoking; but check your instrumentation. Pretty sure it measures the results of fields. Start with what is known. Charge. Is there a particle in its center? A Logical conclusion. No one owns logic! Try if yes, it has not been demonstrated. a neutron is composed of two, yet; particle? If none then a neutron, composite. Diametrical Spherical fields, no beginning, no ending
Hyperfuzzy
milnik
Hyperfuzzy
OK, imagine the life of all equal potential spheres about a charge at rest, relative to you. imagine the field updates as the center moves
now see it for all the charges this paper is talking about
donjoseph
Hyperfuzzy
it was a question about our observation, as we move and its relationship to what is observed, from the perspective of Geometry, a point has no spin; to be callous but respectful, there are no particles.
Spend more thinking about what we know for sure, a field, with a center, it's perfectly geometrical, what is it?