APOD: 2020 November 4 - Fifty Gravitational Wave Events Illustrated

Good morning, Rallypoint. Today's Astronomy Picture of the Day (APOD) is titled "Fifty Gravitational Wave Events Illustrated." You may recall that there are four fundamental forces in Nature: the strong nuclear force, the weak nuclear force, electromagnetism, and gravity. Accelerate a charge and you'll get electromagnetic radiation (think light bulb). But accelerate any mass and you'll get gravitational radiation. And this is where it gets interesting.

Gravitational waves are disturbances in the curvature of spacetime, generated by accelerated masses, that propagate as waves outward from their source at the speed of light. They were proposed by Henri Poincaré in 1905, and subsequently predicted by Albert Einstein in 1916 on the basis of his general theory of relativity. Gravitational-wave astronomy is a branch of observational astronomy that uses gravitational waves to collect observational data from sources of detectable gravitational waves (e.g. binary stars, black holes, supernovae, etc). There are two groups of gravitational-wave observatories on Earth: one in the US (called LIGO) and the other in Europe (called VIRGO).

Over 50 gravitational wave events have now been detected by LIGO and VIRGO. These events mark the distant, violent collisions of two black holes, a black hole and a neutron star, or two neutron stars. The first 50 events are illustrated in today's APOD. Every triplet (three data points) indicate the collision of two objects and the result. The mass of each object is shown in the scale to the left (1 is equivalent to the mass of our Sun, 5 is five times that, etc). Blue dots represent black holes. Orange dots represent neutron stars. Scientists aren't quite sure what to call the white dots, but they do exist and are 2-5 times the size of our Sun.

Can gravitational-wave observations be used as an astronomical tool? Time will tell, I guess. In the meantime, the glimpse inside the mind of the Creator does look like a lot of fun.