On June 30, 2003, the eyes of the international scientific community were riveted on the Plesetsk Cosmodrome in northern Russia, watching the launch of MOST, the new microsatellite of the Canadian Space Agency (CSA).

The flight of the MOST satellite (MOST stands for Microvariability and Oscillations of Stars) was a key step in the ambitious project being carried out with the participation of Steve Torchinsky, a scientist with the CSA's Space Astronomy Program.

"MOST was conceived primarily to measure changes in the luminosity of stars," says Mr Torchinsky. How will a satellite the size of a suitcase manage to do that? With the help of an ingenious telescope it is equipped with. The optical concept used by the instrument makes it possible to optimize diffusion over a greater number of detectors, making MOST capable of detecting even the tiniest variations in luminosity.

The instrument is so powerful that, if humans were capable of doing the same thing, a person standing one kilometre away from a streetlamp would be able to notice an increase in luminosity after moving only half a millimetre closer to the light source!

MOST in Action

The astounding capabilities of MOST will be used to measure the vibrations, or oscillations, of stars. "The Sun, a star that we know well, does not always shine the same way," explains Mr Torchinsky. "Changes in luminosity happen regularly. It is like a bell that rings and emits acoustic vibrations. The larger the bell, the lower its tone. In the same way, the bigger the star, the longer the vibration. MOST therefore makes it possible to study the fundamental vibrations of stars and their harmonics - their various frequencies - and compare them to those of the Sun."

The study of asteroseismology therefore provides us with data - such as the density of the star and the pressure of its surface layers - which we can use, along with the star's temperature and mass, to determine that star's age.

"With MOST, we will finally be able to determine the dynamic composition of stars," says Mr Torchinsky. "In addition to seeing what is found on the surface, we will also be able to discover what is hidden inside the stars, and thus be able to understand their innermost nature."

On the Trail of New Planets

In 1995, astronomers discoveredthe existence of a planet orbiting a star other than the Sun. Today, we believe that the galaxy could contain billions of these extrasolar planets but, to date, we have been able to detect only about a hundred of them. This was done indirectly, by observing their gravitational effect on neighbouring stars. However, thanks to the sensitivity of MOST, we will now be able to directly detect the light reflected by an extrasolar planet.

"MOST sees the light reflected on planets and notes minuscule variations in luminosity," says Mr Torchinsky. "This is a different system of observation, which will provide us with data we never had access to before, since no other telescope - not even Hubble - is capable of collecting this type of information."

A Very Busy Schedule

Although MOST has just been launched, it already has its work cut out for it. Its schedule for the next two years is busy indeed. "The use of MOST has been planned for the next two years," says Mr Torchinsky. "The satellite's activities were determined based on scientific priorities and the visibility of the stars. Consequently, we will give priority to stars that resemble the Sun and to some extrasolar planets."

In its third year of operation, MOST, whose operational life is estimated at two years but which is expected to continue functioning optimally for five years, could be made available to groups of scientists other than the original research team.

"The satellite could even be used for educational purposes by enabling schools to propose experiments that take advantage of the unique capabilities of MOST," emphasizes Mr Torchinsky. "There are so many things to study!"

For the Advancement of Science

At the end of the day, the entire international scientific community could benefit from the valuable data acquired by MOST. "Obviously, as is the custom, the scientific team responsible for the project will be the first to look at the results. However, those results will be published in scientific journals as and when they are acquired," affirms Mr Torchinsky. "The data will therefore be made public internationally and will add to the sum of human knowledge."

The MOST experiment will also be used as a cornerstone for a series of similar future experiments, including the European Space Agency's COROT project. MOST is expected to remain a focal point not only for this reason, but also because its attitude control system - a major technological innovation - is generating a great deal of interest.

"This system is exceptional!" says Mr Torchinsky. "Although it is miniature, its pointing remains very accurate. There is no other system like it and, if we prove that the technology does indeed work, demand for it is sure to be great."

Despite his enthusiasm for technological progress, Mr Torchinsky believes that we should focus on the project's initial intent: "For me, the scientific aspect of projects is the most important. We conduct experiments to enrich our fundamental knowledge. This should be the goal that guides how we choose the subjects we study. Technology will follow."

One thing is certain: with its immense potential, we are sure to hear more about MOST in the years to come!