- 3217 - DARK MATTER - the mystery continues? Dark Matter could be even weirder than anyone thought. This mysterious substance that accounts for more than 80% of the universe's mass could interact with itself. Every attempt to explain dark matter using known physics has come up short.
------------------ 3217 - DARK MATTER - the mystery continues?
- What if Dark Matter interacted with itself through a continuum of forces operating in a space with more dimensions than our usual three? Could this model explain the behavior of stars in small galaxies better than traditional, simple dark matter models?
-
- All observations indicate that the dark matter is made of some new kind of particle, unknown to physics. Physicists think:
-
---------------------- That dark matter particles flood each and every galaxy, accounting for more than 80% of the galaxy’s mass.
-
--------------------- That dark matter particles must not interact with light very much, if at all , otherwise we would have seen it by now in astronomical observations.
-
--------------------- That particle must not interact with normal matter very much, if at all, otherwise we would have seen it in particle collider experiments.
-
- Taking these properties together, cosmologists are able to build sophisticated computer simulations of the evolution of large structures in the universe. Those simulations generally match observations, with one interesting caveat.
-
- This simplified picture of dark matter predicts that “small galaxies” should have very high densities of dark matter in their cores, but observations instead show that the dark matter density is relatively flat, so the stuff must be evenly spread out throughout small galaxies.
-
- This is known as the "core-cusp" problem that has been a thorn in the side of dark matter studies for decades. A successful model of dark matter must be able to account for the behavior of small and large galaxies, along with all the other dark matter observations.
-
- One such model is called “self-interacting dark matter“, and like the name suggests it predicts that dark matter does occasionally interact with itself, meaning that dark matter particles can sometimes bounce off each other or even annihilate each other. This self-interaction smooths out regions of high dark matter density, turning cusps into cores in small galaxies.
-
- However, these self-interacting dark matter models have trouble matching other observations, such as galaxy lensing when gravity from a huge amount of matter distorts and magnifies light from certain galaxies behind it and the growth of galaxies in the early universe.
-
- Electrons interact with each other through the electromagnetic force. Quarks interact with each other through the strong force. And so on. But if simply exporting known physics into the realm of dark matter is coming up short, maybe it's time to look at completely new forces in physics.
-
- New models in physics greatly expands possible models of interacting dark matter, allowing for unknown forces to come into play. The goal is to extend the idea of dark matter 'talking' to “dark forces“. Hidden “dark forces” may govern dark matter's interactions.
-
- Instead of a single force that connects dark matter particles, this model includes an infinite spectrum of new forces all working together. This new model requires an extra dimension to the universe, so a four-dimensional space.
-
- The infinite spectrum of forces, each one represented by a new particle with a different mass, allows for a lot of flexibility when constructing the theory of how dark matter particles might interact.
-
- In the theories that explain known physics, when two particles interact with each other, they do so by exchanging a single kind of force-carrying particle. For example, two electrons bounce off of each other by exchanging photons, the carrier of the electromagnetic force. But this new model replaces that single interaction with a continuum, or spectrum, of interactions, all working together to make the interaction happen.
-
- Dark matter interactions could be described by a continuum of exchanged particles rather than just exchanging a single type of force particle.
-
- By adding an extra dimension it follows the concept known as the AdS/CFT correspondence (the "AdS" stands for anti-de Sitter, which is a kind of space-time, and "CFT" stands for conformal field theory, which is a category of quantum theories). Some physics problems that are extremely difficult to solve in our normal 3D space become much easier to solve with when extended to a four-dimensional space.
-
- By employing this mathematical trick astronomers were able to solve how the forces among the dark matter would interact with each other. They could then translate their results to the three dimensions of space and make predictions for how these forces would operate in the real universe.
-
- For the gravitational force or electric force when you double the distance between two particles you reduce the force by a factor of four. A continuum force, on the other hand, is reduced by a factor of up to eight.
-
- This modification to the self-interaction among dark matter particles allowed the researchers to build simulations that match observations of small galaxies, giving them a "core"-like dark matter profile, rather than the "cuspy" one seen in traditional dark matter models.
-
- Cosmologists use dark matter to explain many different observations across the universe, at a wide variety of scales. Further work will reveal if this exotic theory matches the universe that we see.
-
- But astronomers need to hurry up. The Universe we can see is rapidly disappearing. A cluster of thousands of stars may dissolve to become a mob of dozens of blackholes in a billion years. Time flies!
-
- Scientists have also analyzed “globular clusters“, which are densely packed collections of ancient stars. Roughly spherical in shape, they may each contain up to millions of stars. The Milky Way possesses more than 150 globular clusters arranged in a nearly spherical halo around the galaxy
-
- “Palomar 5“, is a globular cluster 11.5 billion years old located in the Milky Way's halo, 65,000 light-years from Earth in the “Serpens constellation“. Palomar 5 is one of the sparsest known globular clusters.
-
- Whereas the average globular cluster is about 200,000 times the mass of the sun and about 20 light-years in diameter, Palomar 5 is about 10,000 times the mass of the sun yet about 130 light-years across, overall making it about 3,000 times less dense than average.
-
- At the same time, Palomar 5 is known for two long tails streaming from it, composed of stars the globular cluster has shed. These spectacular tails span more than 22,800 light-years in length, more than 20 degrees across the sky, or about 40 times the apparent diameter of the full moon. Palomar 5 is one of the few known star clusters with such long tails, making it key to understanding how such tails might form.
-
- Research suggested Palomar 5's tails resulted from the way in which the Milky Way was shredding apart the globular cluster. The galaxy's gravitational pull is stronger on one side of Palomar 5 than the other, tearing it apart, an extreme version of how the moon's gravitational pull causes tides on Earth.
-
- This so-called "tidal stripping" may help explain not only Palomar 5's tails but also a few dozen narrow streams of stars recently detected in the Milky Way's halo.
-
- Scientists had suggested that Palomar 5 formed with a low density, making it easy for tidal stripping to rip it apart and form its tails. However, a number of its stars' properties suggest it was once similar to denser globular clusters.
-
- Palomar 5 may indeed have once been much denser than it is now and that its current sparse nature and its long tails may be due to more than 100 blackholes lurking within it.
-
- Its structure and tails may have resulted from blackholes making up about 20% of the mass of the globular cluster. Palomar 5 may currently possess 124 blackholes, each on average about 17.2 times the mass of the sun.
-
- The gravity of the blackholes slung around stars that got near them, puffing up the cluster and making it easier for the Milky Way's gravity to rip stars away. A billion years from now, Palomar 5 might have ejected all of its stars, leaving behind only blackholes.
-
- Blackholes may come to completely dominate such globular clusters, making up 100% of their mass.
-
- This research suggest these fluffy globular clusters are rich in blackholes and may eventually completely dissolve, resulting in many thin stellar streams. How the Universe is changing. It is hard to keep up.
-
- July 13, 2021 DARK MATTER - the mystery continues? 3217
----------------------------------------------------------------------------------------
----- Comments appreciated and Pass it on to whomever is interested. ----
--- Some reviews are at: -------------- http://jdetrick.blogspot.com -----
-- email feedback, corrections, request for copies or Index of all reviews
--- to: ------ jamesdetrick@comcast.net ------ “Jim Detrick” -----------
--------------------- --- Wednesday, July 14, 2021 ---------------------------
No comments:
Post a Comment