July 1, 2005

Amazing Discoveries from Canada’s ‘Humble Space Telescope’

Longueuil -- Soon after its launch two years ago by the Canadian Space Agency (CSA), Canada's "Humble Space Telescope" started making amazing observations-beyond the capacity of any other Earth- or space-based instrument. MOST, our suitcase-sized space telescope orbiting at 820 km, can fix its gaze upon a single star for up to eight weeks at a time. And with its unique combination of steady observation time and precision pointing, MOST can look for subtle variations in stars that are impossible to observe from Earth.

Shaking up accepted theories One of the first discoveries made by MOST and its science team is causing astronomers to reconsider theories about some stars. The prestigious science journal Nature published the unexpected findings of the team, headed by Dr. Jaymie Matthews of the University of British Columbia, in July 2004.

Procyon, one of the best-known stars in the galaxy, showed none of the pulsations predicted by over 20 years of theory and observations from Earth. To the team's amazement, Procyon turned out to be a flatliner. The finding has led many astronomers working on future space missions to go back to their computers and redefine their models.

Is a star obeying a planet?

MOST also found a remarkable planetary system where a giant planet seems to be forcing its parent star to rotate in lockstep with the planet's orbit. "The interactions between the star and the giant planet in the tau Bootis system are unlike anything astronomers have seen before," said Dr. Matthews. It's likely that only the surface layers of gas in the star have succumbed to the planet's influence, just as the Moon causes a bulge in the water layer of the Earth's surface creating the tide, but does not force the whole mass of Earth to rotate in step.

Bizarre star brightens like clockwork

MOST has given astronomers Laure Lefvre and Anthony Moffat (both of the Universit© de Montr©al), and Sergey Marchenko (Western Kentucky University) new clues about an exotic star, at least ten times more massive than our Sun, spewing gas into space at a rate of more than 100 trillion tonnes per second. The MOST team spent five weeks studying the star and have found a pattern in its erratic behaviour.

This type of massive star has long been known to exhibit complex, seemingly chaotic, brightness variations associated with the turbulent high-speed winds they eject into space. But steady observation by MOST revealed a clock in the chaos: a stable variation pattern that repeats every 10 hours. "For astronomers studying massive stars, finding a clock in this type of star is like finding the Rosetta stone," says team member Laure Lefvre.

Tuning theoretical models to stars

Dr. David Guenther of Saint Mary's University, in Halifax, Nova Scotia, and the MOST science team have discovered "out-of-tune" vibrations in the nearby sun-like star eta Bootis. Dr. Guenther explains, "Our theoretical star models are slightly out of tune compared to eta Bootis. This means we need to tweak our computer models." If eta Bootis is used as a reference, like a stellar tuning fork, the adjusted computer models will help astronomers better understand our own star, the Sun.

Playing hide-and-seek with a far-away planet

MOST is so sensitive it can detect the presence of planets orbiting distant stars by measuring variations of light in the system. Scientist can even deduct indications of the atmosphere and cloud cover of exoplanets, that is, planets orbiting stars other than the Sun.

At the end of summer 2005, the MOST science team will set the telescope on a 45-day stakeout to observe planet HD209458b, discovered earlier this year by NASA's Spitzer Space Observatory. They hope to get a clearer picture of the composition of the planet's atmosphere and weather-its temperature, pressure, and cloud cover.

MOST (for "microvariability and oscillations of stars") is a Canadian Space Agency mission. Dynacon Inc. of Mississauga, Ontario, is the prime contractor for the satellite and its operation, with the University of Toronto Institute for Aerospace Studies (UTIAS) as a major subcontractor. The University of British Columbia (UBC) is the main contractor for the instrument and scientific operations of the MOST mission. MOST is tracked and operated through a global network of ground stations at UTIAS, UBC, and the University of Vienna.


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