Written by Chris Lintott, a popular British astrophysicist, Oxford University professor and presenter of BBC’s Sky at Night television programme, “Our Accidental Universe” covers a range of the most interesting topics in modern astronomy. All of these topics are centred around the premise that many of the most significant discoveries in astronomy and space science are made serendipitously by fortuitous accidents leading to unexpected results. Chris notes that Meg Urry, Professor of Physics and Astronomy at Yale, takes this further, stating that she can't think of a single major astronomical discovery that had been planned in advance. After all, how can you intentionally look for something unknown and yet to be undiscovered?

Significant examples covered in Our Accidental Universe include Karl Jansky inadvertently introducing the idea of Radio Astronomy. In 1933 Jansky, an engineer working for Bell Telephone Laboratories, discovered radio waves emanating from the Milky Way. Not knowing the source, he called this phenomenon “Star Noise”. By chance he had detected Sagittarius A* at the centre of our galaxy - the radio waves emanating from the hot disc of material around the supermassive black hole. Thus the concept of listening to the universe was born and radio astronomy would become an important supplement to optical observations.

Radio astronomy then opened the door to many other accidental discoveries, such as Jocelyn Bell finding a sharp regular pulsing signal whilst scanning the heavens for random fluctuations in the intensity of celestial radio waves. Bell and her advisor, Anthony Hewish, initially thought they might have detected a signal from an extraterrestrial civilization which they jokingly called LGM-1, which stood for “Little Green Men.” After finding several other similar signals, she realised that she had inadvertently discovered pulsars, the extremely dense and rapidly rotating neutron stars.

Some discoveries are of such significance they alter humanity's understanding of the Universe. When Bell Labs physicists, Arno Penzias and Robert Wilson, set out to map radio signals from the Milky they found an unexplained background noise that interfered with their observations and remained once the effects of both nearby and distant weather had been removed. Finding that the signal was observed to be the same strength in whichever direction their antenna was pointed in, they had stumbled across the oldest light in the Universe - the cosmic microwave background radiation which represents the faint remnant glow of the Big Bang.

Interestingly, another main thread that seems to link the chapters in the first half of the book illustrates humanity's fascination with finding extraterrestrial life. This is addressed directly in the first chapter which spans the topic from Lowell’s thoughts about Schiaparelli’s “canals” on Mars, through to SETI’s quest for evidence of extraterrestrial civilisations and the unusual signals detected by the current Breakthrough Listen initiative. A chapter on the fountains of Enceladus has us wondering about the potential for life in the subsurface oceans of the outer planet moons and the peculiar behaviour and unexplained acceleration of Oumuamua, our oddly-shaped visitor from beyond the Solar System described in the following chapter, led to speculation about it being an alien probe sent to spy on us!

In the curiously titled “Penguins over Venus” Chris describes how our hostile planetary neighbour became the latest and much-debated candidate for alien microbial life when phosphine, a biomarker, was discovered in its atmosphere. This was another serendipitous discovery, this time made by the James Clerk Maxwell Telescope (JCMT) to test the principle of looking for phosphine in the atmosphere of exoplanets (and give the aged telescope struggling for funds something to do). It is amazing that so many of the most interesting astronomical topics insist on leading back to the big question “Are we alone”?

The second half of the book concentrates on advancements in observing and mapping the universe. Perhaps the ultimate expression of serendipitous discovery is illustrated by Chris's own Galaxy Zoo project. This has hundreds of thousands of volunteers online sorting through masses of detailed observational data, classifying objects and looking for anything unusual or unexpected. Chris notes that on over a hundred occasions, Hubble has pointed at something first identified by someone without any formal astronomical training.

In this book, Chris conveys a lot of information without getting bogged down with overly technical language so a layman can enjoy a pleasant and informative cover-to-cover read. It also benefits from having a handy glossary at the back together with a comprehensive section for further reading and a full index. Written in an enthusiastic, conversational and easy-to-read style, covering many of the current most fascinating astronomical topics, “Our Accidental Universe” will undoubtedly appeal to veteran and novice space-science enthusiasts alike.