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Oct08-Foreword.pdf

Unlike most other scientists, an astronomer does not have direct access to the objects he is researching. As a matter of fact, except for a few cases (solar wind and neutrinos, lunar samples, meteorites, …), all information originating from the Universe is transmitted to us by light. Because it has the ability to interact with matter, it keeps a lasting impression of the environment where it was born or has had interaction with. One of the greatest challenges in astronomy is thus to extract, using methods ever more clever, the maximum information from photons that crossed through space over thousands, if not billions, of years. A giant step forward was taken nearly 400 years ago when Galileo Galilei pointed a small and modest telescope towards the sky. Technological developments have since considerably increased the dimension and visual acuity of telescopes (segmented mirrors, adaptive optics), the quantum efficiency of detectors (often close to 100%), the detectable wavelength range (from radio waves to gamma rays), as well as all the specific measurement techniques such as photometry, spectroscopy and polarimetry. Theoretical developments are not overlooked with the always increasing use of numerical modeling. Canada has been actively participating for a long time in the development of international astronomy, with its super computers, local and national infrastructures (Mont Mégantic Observatory in the Eastern Townships, DRAO in the Okanagan Valley, DAO in Victoria, to name a few) or in collaboration with other countries, on Earth (Canada-France-Hawaii, Gemini, ALMA telescopes) and in space (James Webb, MOST, FUSE or UVIT telescopes).

To celebrate the upcoming International Year of Astronomy, this special issue offers an overview, very incomplete though, of Canadian astronomy and its research; some marginal (but so fascinating!), other more conventional, but all leading edge in their respective field.

Life on our planet depends on the sun’s luminosity, which originates from nuclear reactions within its core. During the last 4 billion years, it has substantially increased, but also fluctuated to a lesser degree, depending on the intense magnetic activity on the surface. The article by Charbonneau, Crouch and Tapping demonstrates the modeling of these solar irradiance variations.

At the root of the media frenzy which took place in 2006 following the withdrawal of Pluto as a planet by the International Astronomical Union are the huge advances realized during the last decade in recognizing the external regions of the solar system. Gladman and Kavelaars, which are credited with discovering many moons of Jupiter, Saturn, Uranus and Neptune, report on the often complex interactions between Neptune and the thousands of objects that shape the Kuiper belt, of which Pluto is now only one of the most massive components.

Polarization is without contest one of the less exploited properties of light in astronomy. With a relatively low level, therefore difficult to measure, polarization detects the presence of a magnetic field in the interstellar medium, as demonstrated by Brown and her colleagues in the article on one of the most important mappings of the Milky Way, produced at the radio telescope in Penticton.

The next four articles touch on one of the hottest themes in contemporary astrophysics, the formation and evolution of galaxies, but under completely different angles. First, Venn states the importance of the spectroscopic study on metal-poor stars, witnesses to the first phases of development of the Milky Way and its neighbours. As Martel explains, the advent of always more powerful computers and of innovative algorithms allowing the simulation of the complex gravitational and hydrodynamic processes at play during collisions between galaxies help us better understand the morphological, dynamical and chemical evolution of galaxies. These numerical simulations are brought forth in the results of a long term observation program taken on several years ago by Abraham and his team through a new technique implemented at the Gemini telescope; this research has made it possible for the first time to measure the properties of galaxies when the Universe was only three to six billion years old. This article also demonstrates that the rate of star formation in the Universe has dramatically dropped since that era and that this tendency will increase until the depletion of all gas in the galaxies. Finally, the use of space telescopes to probe the heavy ultraviolet radiation emitted during star-forming bursts is well demonstrated by Robert, who reminds us of the role taken by the Canadian Space Agency in the development and commissioning of telescopes in space.

From the solar system to distant galaxies, these articles touch on very diverse themes with theoretical and observational approaches, which we hope will fill the reader with wonder and food for thought.

Laurent Drissen, Université Laval, Québec
Guest Editor, Physics in Canada

Comments of readers on this foreword are more than welcome.

Laurent Drissen est professeur au département de physique, de génie physique et d'optique de l'Université Laval. Il est aussi titulaire de la chaire de recherche du Canada sur les étoiles massives et l'imagerie hyperspectrale depuis 2001.

Professor of Physics at Laval University, Laurent Drissen has always been fascinated by the most massive stars. He also works on the development of imaging Fourier transform spectrometers to understand the properties of the ionized interstellar medium.