Monday, May 20, 2024

Astronomers Discover the Milky Way Torus

I love to say "I told you so"! Yet another in a long line of scientific discoveries verifies the cosmology of A Simple Explanation of Absolutely Everything. Nice going, scientists! Here's a reprint from SciTech Daily, shared with us by a longtime ASEOAE reader. Thank you, Karl!

Galactic Rings of Power: Astronomers Uncover Massive Magnetic Toroids in the Milky Way Halo

By CHINESE ACADEMY OF SCIENCES MAY 14, 2024

Magnetic fields in the halo of the Milky Way have a toroidal structure, extending in the radius range of 6000 light-years to 50,000 light-years from the Galaxy center. The Sun is at about 30,000 light-years. Credit: NAOC

Astrophysicists have discovered large magnetic toroids in the Milky Way’s halo, which impact cosmic ray propagation and the physics of interstellar space. Their research, based on extensive Faraday rotation data, reveals that these toroids extend across the galaxy, confirming the presence of significant toroidal magnetic fields.

A long-standing unsolved question at the frontier of astronomy and astrophysics research is the origin and evolution of cosmic magnetic fields. It has been selected as one of the key areas of investigation for many major world-class radio telescopes, including the Square Kilometer Array (SKA) currently under construction. Determining the large-scale magnetic field structures in the Milky Way has been a major challenge for many astronomers in the world for decades.

Discovery of Magnetic Toroids

In a new study published in The Astrophysical Journal on May 10, Dr. Jun Xu and Prof. Jinlin Han from the National Astronomical Observatories of the Chinese Academy of Sciences (NAOC) have revealed huge magnetic toroids in the halo of the Milky Way, which are fundamental for cosmic ray propagation and provide crucially constraint on the physical processes in the interstellar medium and the origin of cosmic magnetic fields.

Prof. Han, a leading scientist in this research field, has determined the magnetic field structures along the spiral arms of the Galactic disk through a long-term project of measuring the polarization of pulsars and their Faraday effects. In 1997, he found a striking anti-symmetry of the Faraday effects of cosmic radio sources in the sky with respect to the coordinates of our Milky Way galaxy, which tells that the magnetic fields in the halo of the Milky Way have a toroidal field structure, with reversed magnetic field directions below and above the Galactic plane.

Challenges in Measuring Magnetic Fields

However, to determine the size of these toroids or the strength of their magnetic fields has been a tough task for astronomers for decades. They suspected that the anti-symmetry of the sky distribution of Faraday effects of radio sources could be produced merely by the interstellar medium in the vicinity of the Sun because pulsars and some nearby radio-emission objects, which are quite near to the Sun, show Faraday effects consistent with anti-symmetry. The key is to show whether or not magnetic fields in the vast Galactic halo had such a toroidal structure outside the vicinity of the Sun.

Innovative Research Methods

In this study, Prof. Han innovatively proposed that the Faraday rotation from the interstellar medium in the vicinity of the Sun could be counted by the measurements of a good number of pulsars, some of which have been obtained recently by the Five-hundred Aperture Spherical radio Telescope (FAST) by themself, and then could be subtracted the contribution from the measurements of background cosmic sources. All Faraday rotation measurement data in the past 30 years were collected by Dr. Xu.

Through data analysis, scientists found that the anti-symmetry of the Faraday rotation measurements caused by the medium in the Galactic halo exists in all the sky, from the center to the anti-center of our Milky Way, which implies that the toroidal magnetic fields of such a odd symmetry have a huge size, existing in a radius range from 6000 light-years to 50,000 light-years from the center of the Milky Way.

Conclusion and Impact

This study has significantly advanced our understanding of the Milky Way’s physics and marks a milestone in research on cosmic magnetic fields.

Reference: “The Huge Magnetic Toroids in the Milky Way Halo” by J. Xu and J. L. Han, 10 May 2024, The Astrophysical Journal.
DOI: 10.3847/1538-4357/ad3a61

Thursday, May 16, 2024

Scientists considering a torus shaped universe

Here's a reprint of a Science News article dated May 13, 2024.

The universe may have a complex geometry — like a doughnut

Scientists previously considered only a small subset of possible topologies

Scientists are considering whether the universe might have a complicated topology, represented by a doughnut shape in this artist’s conception.

J. LAW/ESOEmail

The cosmos may have something in common with a doughnut.

In addition to their fried, sugary goodness, doughnuts are known for their shape, or in mathematical terms, their topology. In a universe with an analogous, complex topology, you could travel across the cosmos and end up back where you started. Such a cosmos hasn’t yet been ruled out, physicists report in the April 26 Physical Review Letters.

On a shape with boring, or trivial topology, any closed path you draw can be shrunk down to a point. For example, consider traveling around Earth. If you were to go all the way around the equator, that’s a closed loop, but you could squish that down by shifting your trip up to the North Pole. But the surface of a doughnut has complex, or nontrivial, topology (SN: 10/4/16). A loop that encircles the doughnut’s hole, for example, can’t be shrunk down, because the hole limits how far you can squish it.

The universe is generally believed to have trivial topology. But that’s not known for certain, the researchers argue.

“I find it fascinating … the possibility that the universe might have nontrivial or different types of topologies, and then especially the fact that we think we might be able to measure it,” says cosmologist Dragan Huterer of the University of Michigan in Ann Arbor, who was not involved with the study.

A universe with nontrivial topology might be a bit like Pac-Man. In the classic arcade game, moving all the way to the right edge of the screen puts the character back at the left side. A Pac-Man trek that crosses the screen and returns the character to its starting point likewise can’t be shrunk down.

Scientists have already looked for signs of complex topology in the cosmic microwave background, light from when the universe was just 380,000 years old. Because of the way space loops back on itself in a universe with nontrivial topology, scientists might be able to observe the same feature in more than one place. Researchers have searched for identical circles that appear in that light in two different places on the sky. They’ve also hunted for subtle correlations, or similarities, between different spots, rather than identical matches.

Those searches didn’t turn up any evidence for complex topology. But, theoretical physicist Glenn Starkman and colleagues argue, there’s still a chance that the universe does have something in common with a doughnut. That’s because earlier research considered only a small subset of the possible topologies the universe could have.

That subset includes one type of nontrivial topology called a 3-torus, a cube that loops back on itself like a 3-D version of the Pac-Man screen. In such a topology, exiting any side of that cube brings you back to the opposite side. Searches for that simple 3-torus have come up empty. But scientists haven’t yet searched for some 3-torus variations. For example, the sides of the cube might be twisted relative to one another. In such a universe, exiting the top of the cube would bring you back to the bottom, but rotated by, for example, 180 degrees.

The new study considered a total of 17 possible nontrivial topologies for the cosmos. Most of those topologies, the authors determined, haven’t yet been ruled out. The study evaluated the signatures that would appear in the cosmic microwave background for different types of topologies. Future analyses of that ancient light could reveal hints of these complex topologies, the researchers found.

The search is likely to be computationally challenging, probably requiring machine learning techniques to speed up calculations. The researchers also plan to hunt for signs of nontrivial topology in upcoming data from surveys of the distribution of galaxies in the cosmos, for example from the European Space Agency’s Euclid space telescope (SN: 12/20/23).

There’s good motivation to look for nontrivial topology, says Starkman, of Case Western Reserve University in Cleveland. Some features of the cosmic microwave background hint that the universe isn’t the same in all directions (SN: 12/23/08). That kind of asymmetry could be explained by nontrivial topology. And that asymmetry, Starkman says, is “one of the biggest new mysteries about the universe that hasn’t gone away.”