“Spinning Stardust into Gold” by Dr. Danny R. Faulkner (review)

The year 2017 witnessed a pivotal moment in astronomical history with the detection of GW170817 – the collision of two neutron stars 130 million light years away. This event, beyond its scientific significance, captured the public imagination with the intriguing notion of potentially generating an immense amount of gold. While the reality of such a scenario is more nuanced, GW170817 remains a landmark discovery, offering unprecedented insights into the universe's violent and dynamic processes.

Decoding the Enigma of Neutron Stars:

Before delving into the complexities of GW170817, understanding the nature of the celestial participants is crucial. Neutron stars, aptly named for their composition primarily of neutrons, defy conventional notions of size and density. Despite their diminutive diameter of a few miles, they pack a remarkable punch, cramming the mass equivalent of all the cars ever built into a single teaspoon. Conceptualized in the 1930s and confirmed in 1967, these remarkable objects hold a unique place in the stellar graveyard, existing as the remnants of massive stars that have undergone supernovae explosions.

Einstein's Elusive Ripples: The Power of Gravitational Waves:

Another key element in the story of GW170817 is the concept of gravitational waves, ripples in the fabric of spacetime predicted by Albert Einstein. Their incredibly faint nature makes detection extremely challenging. Although indirectly observed in 1974, it wasn't until 2015 that the Laser Interferometer Gravitational-Wave Observatory (LIGO) achieved the remarkable feat of directly detecting them, arising from the merger of two black holes. This groundbreaking discovery, later awarded the 2017 Nobel Prize in Physics, marked a significant leap in our understanding of gravity and the universe's most violent events.

The Celestial Dance of GW170817: Unveiling a Multi-Messenger Symphony:

The data from GW170817 unfolded a story far richer than just the collision of two massive objects. Unlike the black hole merger, this event not only generated the characteristic ripples in spacetime but also produced a spectacular multi-messenger symphony across various wavelengths of the electromagnetic spectrum.

The Curtain Rises: The Explosive Birth of a Gamma-Ray Burst:

The first act in this cosmic drama unfolded within seconds of the gravitational wave signal subsiding. Both the Fermi Gamma-Ray Space Telescope and the INTEGRAL observatory detected a powerful burst of gamma rays, designated GRB 170817A. This observation significantly bolstered the theory that GRBs, some of the most energetic phenomena in the universe, originate from the cataclysmic mergers of neutron stars.

The Dazzling Encore: The Emergence of a Kilonova:

Following the dramatic opening act, another awe-inspiring phenomenon emerged – the birth of a kilonova. This short-lived but luminous transient, aptly named for its brief lifespan and association with the immense forces involved, originates from the debris ejected at high velocities during the merger. The intense heat and pressure within this ejected material forge a variety of elements heavier than iron, including gold. However, the actual amount of gold produced is estimated to be significantly less than the sensationalized claims and likely dispersed throughout the vast interstellar space.

Beyond the Alchemical Dream: Unveiling the Universe's Secrets:

While the notion of "spinning stardust into gold" may be an oversimplification, the scientific significance of GW170817 cannot be overstated. It represents the first-ever simultaneous observation of gravitational waves and light from a single source, offering invaluable insights into the violent and dynamic processes occurring in the cosmos. The event has opened a new era in multi-messenger astronomy, allowing us to study the universe through various "eyes" and piece together a more comprehensive picture of its hidden wonders.

GW170817 stands as a testament to the power of scientific collaboration and technological advancements. It serves as a reminder that the universe continues to hold many secrets waiting to be unveiled, and with each new discovery, we gain a deeper understanding of the incredible dance of matter, energy, and space-time that shapes the cosmos.

Editors comments:

Gravity's Speed and Gravitational Waves:

According to Einstein's theory of general relativity, gravity isn't a force acting instantaneously between objects, but rather a result of the curvature of spacetime caused by mass and energy. This curvature propagates outward at the speed of light (c), and that's the speed associated with gravitational waves. It's crucial to understand that gravitational waves aren't the same as gravity itself.

Nuances about the "One-Way Speed" of light:

The statement "one-way speed of gravity" can be misleading. Gravity isn't a physical object traveling at a specific speed. Instead, it describes the influence of mass and energy on spacetime, which propagates at the speed of light. This means any changes in the gravitational field, like those caused by moving objects, will propagate outward at “c”, not the "influence" of gravity itself.

GW170817 and Measuring Speed:

The GW170817 event 130 million light years away provided an incredible opportunity to study the interaction of gravitational waves and light from the same source – the colliding neutron stars. Scientists were able to compare the arrival times of gravitational waves and electromagnetic waves (like gamma rays) from the event. Since both travel at the speed of light, any significant difference in arrival times would have indicated a deviation from the established speed of light for either type of wave. However, no such discrepancy was observed. This observation strengthens the scientific consensus that gravitational waves indeed travel at the speed of light, further supporting the predictions of general relativity.

Moving Forward:

GW170817 and similar future detections will continue to refine our understanding of gravity and its effects. Instead, these observations provide valuable insights into the propagation of changes in the gravitational field at the speed of light.