March 2011 - Issue #12
A bestiary of galaxies
Story by Julian Cribb
View articles in related topics: Astrophysics
Since the advent of radioastronomy in the 1930s, astrophysicists have been able to observe galaxies not merely through the brilliance of their visible light – but increasingly across every accessible wavelength in the electromagnetic spectrum, from high-energy gamma rays and x-rays to the infrared and longest radio wavelengths.
This ability to view galaxies in all their moods, revealing the potent energies at work within them, is the inspiration for a unique new atlas compiled by Swinburne astronomer Dr Glen Mackie.
The Multiwavelength Atlas of Galaxies, published by Cambridge University Press in 2010, presents an in-depth view of 35 of the best known galaxies. Its images have been contributed by Dr Mackie and more than one hundred astronomy colleagues using the Hubble Space Telescope, Chandra X-ray Observatory, Australia Telescope Compact Array, Spitzer Space Telescope, Parkes 64-metre dish and many other space- and ground-based telescopes.
The atlas is a visual feast of more than 250 colour images to delight both aspiring scientist and lay reader alike, and is the first to display the extraordinarily contrasting faces of the same object viewed at different wavelengths.
It has four parts. The first introduces galaxies, discusses the atlas sample, categories of galaxies and properties of the sample. Part two describes the various origins of radiation emitted by galaxies and presents some important galaxy research topics that use multiwavelength observations.
Part three discusses multiwavelength radiation from the Galactic Centre and finishes with all-sky multiwavelength images of our Galaxy.
Part four comprises the multiwavelength atlas images with scientific explanations of what is going on within each galaxy. The book also has appendices describing the telescopes and instruments used, image sources, technical descriptions of each image, a cross-referenced list of galaxies, and plots of spectral energy distributions.
“As a young postdoc at Harvard I was studying one galaxy – NGC1316 – in particular detail in the optical spectrum, and it became clear it had recently, in the past one to two billion years, consumed several smaller galaxies,” Dr Mackie explains. “In order to work out their types I went to data from X-ray, radio and other wavelengths.”
The result, he remembers, was a rather beautiful suite of images, each contrasting dramatically with the others and, in total, providing important new information on the evolutionary history of each galaxy. Dr Mackie promptly created a web page and began to add views of other galaxies across the electromagnetic spectrum – and this soon caught the eye of Cambridge University Press.
“Historically, we’ve tended to look at galaxies mainly at optical wavelengths – but that is really only about 10 per cent of the full story. Looking across the full spectrum you see what’s going on not only with stars, but with gas, dust, even electrons.”
Dr Mackie envisaged the atlas originally as a textbook for astronomy students and a reference for professional astronomers, but it quickly became apparent that its potential audience is far larger, including members of the general public hungry to learn more about the processes that have shaped and structured our universe.
MORE INFORMATION
The Multiwavelength Atlas of Galaxies went on sale internationally via the Cambridge University Press catalogue in December 2010. A sample of its visual and informational delights can be viewed here www.swinburne.edu.au/astronomy.
