Cosmic Explosions, Expanding Universe, and Earth's Peril: An Astronomer Responds to Frequently-Encountered Inquiries
In the vast expanse of the Universe, one of the most enigmatic and powerful events are gamma-ray bursts (GRBs). These bursts of high-energy radiation, lasting mere fractions of a second, have been observed from as far back as 13 billion years ago, thanks to the light from these events having travelled through the expanding Universe for billions of years.
The origin of GRBs is closely linked to the deaths of massive stars and the mergers of binary neutron stars. As a large enough star collapses, it initially forms a black hole that is only a few miles across. The star's rotation initially causes the material to be drawn into a disc around it, setting the stage for the creation of a GRB.
A fair fraction of the star's potential energy gets transformed into heat, rotational velocity, magnetic energy, and so on. Under certain ways of looking at distance, faraway galaxies are receding from us faster than the speed of light. However, if we regard the distance between us and distant galaxies as expanding faster than the speed of light, then nothing is moving faster than the speed limit relative to other matter in its vicinity.
Some of the energy from the collapsing star goes into powering very fast-moving jets or beams of outflowing plasma, which create the GRBs we observe. The process of how GRBs are created is still being researched, but it's probable that the star's magnetic field is wound up like a rubber band, throwing out matter when it unwinds.
The research primarily focuses on transient phenomena, particularly GRBs. Despite their rarity, even rarer in galaxies like ours, it's important to improve our understanding of GRBs to identify potentially threatening systems nearby. Gamma-ray bursts are so powerful that they could pose a threat to life on Earth if one occurred in the Milky Way.
In recent years, notable GRBs have been observed in events such as GRB 190114C (detected in January 2019), which originated from a distant galaxy approximately 4.5 billion light-years away, and GRB 230307A (observed in March 2023), linked to a neutron star merger in a galaxy about 6 billion light-years distant.
The Big Bang theory, which challenges our intuition about how we can see light from such distant events that have travelled for billions of years, assumes a symmetrical and infinite Universe. In the Big Bang theory, the Big Bang isn't an explosion in space, but an explosion of space.
As we continue to unravel the mysteries of GRBs, we gain a deeper understanding of the Universe and our place within it. The study of these cosmic phenomena promises to reveal more about the nature of the Universe and the fundamental forces that govern it.
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