“Just because we happen to live in a region that is overwhelmingly dominated by matter doesn’t preclude the existence of other regions of space that are instead dominated by antimatter,” observes Dan Hooper, head of the Theoretical Astrophysics Group at the Fermi National Accelerator Laboratory (Fermilab) and Associate Professor of Astronomy and Astrophysics at the University of Chicago.
“If a galaxy somewhere in our universe collided with or otherwise encountered a galaxy made of antimatter,” wrote Hooper in an email to The Daily Galaxy, “ it would release a violent explosion of gamma rays, with distinctive spectral features. Nothing like this has ever been seen by astronomers, forcing us to conclude that large collections of antimatter must be very rare in our universe, if they exist at all.”
The Standard Model –which explains how the basic building blocks of matter interact, governed by four fundamental force–fails to explain the enduring mystery of why the observable universe contains virtually no antimatter. Physicists believe that at the Big Bang there were equal amounts of matter and antimatter in the early history of the universe – so how did the antimatter vanish? Perhaps it didn’t and resides isolated in some far distant regions of our universe.
If Such Exotic Regions Exist –They Could Contain Life
If such exotic regions do exist with large quantities of antiprotons, antineutrons, and positrons without the presence of any protons, neutrons, or electrons to annihilate with, it would behave just as ordinary baryonic matter does, forming antimatter versions of all of the known types of atoms and molecules, which would undergo the full array of physical and chemical reactions and processes that take place among ordinary matter, creating stars, planets, and galaxies—and could even contain life. “And the light generated from an antimatter star or an antimatter galaxy,” explains Hooper in At the Edge of Time, “would be entirely indistinguishable from that produced by any ordinary star or galaxy.”
As LIGO has shown us with its recent detection of merging neutron stars and supermassive black holes, astrophysical systems pass matter back and forth constantly, with many galaxies in our universe colliding or merging with one another. Even the Milky Way is expected to collide in four billion years in a colossal mashup with its nearest neighbor, the massive Andromeda galaxy, which could eventually eject our solar system into deep space.
The Last Word
“If there were to exist a region that was filled with antimatter instead of ordinary matter, matter and antimatter would annihilate each other rapidly everywhere along the boundary of this region,” Dan Hooper told The Daily Galaxy. “That would lead to distinctive signatures that we just don’t see with our telescopes. If antimatter-dominated regions or objects exist, they must be either very far away from us, or be very isolated from ordinary matter.”
Avi Shporer, Research Scientist, MIT Kavli Institute for Astrophysics and Space Research via Dan Hooper, At the Edge of Time (pp. 90-91). Princeton University Press. Kindle Edition and Theorists suggest ‘Higgs Troika’ may have been responsible for disappearance of antimatter
Image credit: NGC 4258, also known as M106, a spiral galaxy made of ordinary matter, like the Milky Way. NASA/CXC/Caltech/P.Ogle et al; Optical: NASA/STScI; IR: NASA/JPL-Caltech; Radio: NSF/NRAO/VLA