Imagine a time when our best images of the universe were black and white photos. This is the year 1960. Forget about galaxy evolution theory, we didn’t even have mature ideas on how they came to exist. We had no idea how the universe evolved, nor how old it might be. As championed by Sir Fred Hoyle, the “Steady State” theory, where space is non-evolving, infinite, and has been expanding since forever, reigned supreme in an era wholly lacking discriminatory data.

Throughout the 1950s, mysterious bright radio emitting sources were being discovered using the new field of radio astronomy. In the black and white optical photos of 1960, they looked suspiciously star like. Their optical spectra, however, were decidedly not star like.  Curiously, these “quasi-stellar objects,” now called quasars, were too bright in the blue and exhibited strong emission lines that defied identification even by the most seasoned astrophysicists. In 1963, the tenacious Caltech astronomer Maarten Schmidt deciphered the spectral lines of the object known as 3C 273. His calculations indicated that 3C 273 was being whisked away by cosmic expansion at a rate of 15% the speed of light, resided some 2.5 billion light years from Earth, and shined with a power 4 trillion times the Sun. What!?  

Schmidt’s discovery launched an explosive revolution in the astronomical sciences. In fact, it is not hyperbole to resolve that the discovery of quasars made an entirely new science of astronomy. Quasars bequeathed to us the modern era in which we gained the tools to experimentally measure astrophysical phenomena occurring billions of years ago in cosmic time and billions of light years across the known universe.  

Today, after 65 years of concentrated efforts by multiple generations of astronomers, we know that quasars are powered by ravenous supermassive black holes and that they live in the nuclei of distant galaxies. Like otherworldly lighthouses, their high-powered light beams pierce through the universe and probe cosmic history just like a collimated core sample puncturing into the surface of the Earth probes geologic time. When the quasar beam reaches Earth, astronomers spread its light into a spectrum. The exquisitely sensitive complex patterns of absorption lines in these quasar spectra, which are due to countless individual microscopic atomic excitations in the cosmic gas structures comprising the intergalactic and circumgalactic medium, are like the DNA sequences of the universe. Extracting the astrophysics encoded in these “quasar absorption lines” is the revolutionary breakthrough science that yields our modern understanding of the cosmos. By analyzing quasar absorption lines, we continue to sound its origin and evolution. Scientific revolutions move fast; documenting their subsequent development, growing complexities, and broader impacts while still in their midst is like chasing caffeinated free-range chickens. In the case of quasar research, such endeavors can be counted on one hand. 

The two-volume set Quasar Absorption Lines bridges a 40-year chasm of explosive progress since Dan Weedman’s 1986 offering, Quasar Astronomy.1 Since the 1980s, there has been unimagined increases in telescope light gathering power, detector technology, optical design, and computing power. On top of that, the advent of space telescopes opened the gamma-ray, X-ray, ultraviolet (UV), and infrared (IR) electromagnetic windows on the universe. Experimental techniques evolved from “point, shoot, and scratch your head” to highly developed scientific programs capable of constraining Big Bang nucleosynthesis theory, charting the evolution of large-scale structure, precisely measuring both the global ionization and chemical enrichment histories of the universe, and probing the gas cycles and physical processes governing galaxy formation and evolution.

Volume 1 chronicles sixty-five years of quasars absorption line science. Each of the 19 chapters covers a separate sub-field and provides a journey from the first discoveries to the modern theoretical and experimental scientific findings. Volume 2 provides the theoretical and practical tools to carry out cutting-edge quasar absorption line science. It covers atomic and gas physics, application of the cosmological model, radiative transfer in astrophysical gases, analysis of UV, optical, and IR spectra, and cutting-edge scientific analysis methods.

The hope is that, taken together, these two books provide a partial historical record of an era rich in astronomical discoveries, methods, and techniques, as well as contribute to the growth and development of the next generation of quasar spectroscopists and extragalactic astronomers.

1 Weedman, D. 1986, Quasar Astronomy, Cambridge University Press, ISBN: 9780521303187 

This blog has been fully written by the author. There has been no AI assistance.