James Geach

Extragalactic Astronomer / Science Writer

Jim Geach @jgeach

j.geach at herts.ac.uk.

Centre for Astrophysics Research (CAR), University of Hertfordshire, Hatfield, Hertfordshire, AL10 9AB, United Kingdom

Research diary

About me and my research

I am a Royal Society University Research Fellow and Senior Lecturer based in the Centre for Astrophysics Research (CAR) at the University of Hertfordshire. I did my Ph.D. at Durham University under the expert tutelage of Ian Smail. After graduating, I was a post-doc at Durham and Banting Fellow at McGill University before coming to CAR in 2013.

My research focuses on the evolution of galaxies, with a special emphasis on obscured activity, the role of environment, and the properties and evolution of cold gas in and around galaxies. For a complete record of my research, you can find an up-to-date listing of publications and pre-prints at the NASA Astrophysics Data System.

Some of my research in the press:

Galactic blow out
Lyman Alpha Blobs: Galaxies Coming of Age in Cosmic Blobs
Herschel Sees Intergalactic Bridge Aglow With Stars
Galaxy Goes Green in Burning Stellar Fuel
Astronomers Map Dark Matter Throughout the Entire Universe

I also write about science. I like trying to break down complex ideas into simple language, and communicate the cutting edge of astronomical research, in a way that anyone can understand. My first book, Galaxy: Mapping The Cosmos, is published by Reaktion Books:

Galaxy: Mapping The Cosmos

Galaxy: Mapping The Cosmos is published by Reaktion Books.

Galaxy cover

My bookspot:

Some praise for Galaxy:

Astrophysicist Geach goes an order of magnitude further than the usual popular astronomy title - those full of breathtaking images, but little in the way of context - by giving readers the fascinating stories revealed by those images: how galaxies are created, how they evolve, and what they tell us about our universe. The sheer variety is stunning: 'grand design' spirals like our Milky Way; barred spirals; irregular and amorphous galaxies with no discernible structure; dynamic interacting and colliding galaxies where new stars form like popcorn; and quasars, ancient, distant galaxies whose central black holes spew copious amounts of x-ray, ultraviolet, and visible radiation. Living in the Milky Way gives us an insider's view of a typical spiral galaxy, with its broad disc of stars surrounding a bulge or hub of older stars cloaking a supermassive black hole. Geach explores the technology behind modern big telescopes—as well as their instrumentation and techniques—that scientists use to study galaxies as they determine what they're made of, how much is unknown dark matter, and how fast they're receding away from us in our expanding universe. Gorgeous color photos, coupled with clear and engaging explanations of the science behind them, make this book a winner on every level.

Publishers Weekly

Book of the Month... Galaxy: Mapping the Cosmos is a beautifully illustrated exploration of the Universe beyond the Milky Way, and the mysteries and wonders of extragalactic astronomy. Geach is ideally placed to be our guide on this journey - a researcher in the fastchanging field of galaxy evolution, he displays both breadth and depth of knowledge, happily matched by a talent for engaging, nontechnical prose and an eye for a simile... [Galaxy] is an enthralling, detailed and beautiful look at one of the most challenging and exciting areas of modern astronomy, and a great addition to any enthusiast's library.

Sky At Night Magazine

James Geach is actively researching on one of the most exciting frontiers of today’s science: extragalactic astronomy. His book conveys his personal enthusiasm, and offers a clear and highly readable survey of the field’s progress and prospects.

Professor Martin Rees FRS, Astronomer Royal, Institute of Astronomy, Cambridge

Dr Geach brings his personal experience to the fore in describing the latest discoveries in this rapidly developing field of cosmology and galaxy evolution . . . I highly recommend this book for those wanting to share in the excitement of modern astronomy.

Professor Richard Ellis FRS, California Institute of Technology

Galaxies are the building blocks of the Universe. But they are dynamic blocks that have changed and evolved throughout the 13 billion years since their seeds – sown at the very instant of the Big Bang – began to grow. Their trials and tribulations are recounted with great clarity in this short, accessible, yet deep and comprehensve book. What are galaxies made of, why do they have different sizes, luminosities and morphologies, how have they managed to grow gigantic black holes in their midst, all these questions are posed – and answered as far as current knowledge permits – in an engaging and absorbing way by James Geach. As a practising professional astronomer at the cutting edge of galaxy research, Geach has managed to convey the vibrancy and excitement of research at the very forefront of human knowledge.

Professor Carlos Frenk FRS, Director of the Institute for Computational Cosmology, Durham University

Articles and features

Check out "The Lost Galaxies", a feature article I wrote for Scientific American.This article looks at the issue of 'missing baryons', or the inefficiency of galaxy formation from the standpoint of where most of the gas in the Universe ended up. This article was also featured in the August 2014 Special Edition of Scientific American titled Secrets of the Universe: past, present and future

I also write the occasional piece on Medium.


Rob Crain and myself have been developing a set of tools to create bespoke visualizations of cosmological simulations and volumetric observational data. We have created fully stereoscopic IMAX-scale movies, and our work has appeared on the front cover of Nature and Scientific American. A few examples of our work:

Field of streams
Scientific American
Late evolution SCUBA-2