Magnetic Fields are Present Everywhere in the Universe, But Where Do They Come From?
How the universe has such vast magnetic fields is one of the most pressing questions in astrophysics.
Recently, researchers proposed a completely new explanation. They suggest that the magnetic fields in the universe originated from a “dust battery” that activated when the first stars appeared.
Magnetic field of a muon particle (Image: Newton Henry Black/ Wikimedia commons).
Magnetic fields are ubiquitous in the vastness of space. The Earth’s magnetic field deflects harmful cosmic radiation, causes compasses to shake, and guides migratory birds.
Other planets and stars also possess magnetic fields. The magnetic fields of Jupiter and the Sun are stronger than that of Earth. The entire Milky Way galaxy has its own magnetic field, although it is about one million times weaker than Earth’s. Nevertheless, it spans tens of thousands of light-years across the galaxy.
Astronomers have identified even larger magnetic fields, some so vast that they encompass entire galaxy clusters stretching several million light-years.
So, where do these enormous magnetic fields come from? Although they are relatively weak, they are extraordinarily extensive. Therefore, whatever generates them must originate from incredibly powerful energy sources.
For decades, astronomers believed there were several mechanisms primarily based on a dynamical process that takes weak “seed” fields and amplifies them to their current values.
However, this raises the question of where these weak seed fields come from in the first place.
Recently, astronomers have proposed a completely new explanation.
In this scenario, the context is the dawn of the universe, when it was only a few hundred million years old, and the first stars and galaxies began to shine. After the first stars died, they left behind remnants of heavier elements. These elements found each other in interstellar space and formed the first dust particles.
These dust particles often carry electric charges due to bombardment by radiation and friction among themselves. When the second generation of stars ignited, their intense light penetrated all the surrounding gas and dust.
If these stars were sufficiently powerful, their radiation could push the dust particles to move through the remaining gas. The charged dust particles in motion would generate a weak current, but on a large scale, akin to a copper wire stretching 1,000 light-years.
Due to the uneven filtering of radiation through interstellar gas, the moving dust particles tend to cluster at certain points and disperse more thinly at others. This creates varying electric currents from one place to another, which, through electromagnetic laws, naturally generates magnetic fields.
In this new study, scientists discovered that these magnetic fields are very weak, only about 1 billionth of the strength of Earth’s magnetic field, but still sufficient for other astrophysical processes to latch onto that seed field and create the magnetic fields we see today.
Nonetheless, this remains merely a hypothesis. The outcome of this hypothesis is a formula that simulates the evolution of galaxies and their magnetic fields. This is a significant step in comparing this hypothetical magnetic field with the magnetic fields observed in the universe.
Traveling back in time to see where the magnetic fields in the universe originated is impossible, but we can utilize ideas and hypotheses like this to gradually reconstruct the picture of the past, all in the pursuit of understanding the vast universe of which our home, Earth, is a part.
