14 DAY TRIAL // Started in 2003, the SuperNova Legacy Survey is the first project aiming to measure the distances to far supernovae.
So far, the 40 researchers behind it have succeeded to measure the distances to 71 supernovae that exploded between 2 and 8 billion years ago.
Measuring the distance to faraway supernovae is a key tool for cosmologists. Supernovae are exploding stars, known to have similar brightness whatever their location in other galaxies. Observing these exploding stars can thus make it possible to measure their distances: they are known as "standard candles" for measuring long distances in the Universe.
Measurement of these distances revealed a startling phenomenon; in the late 1990s, astronomers found that the expansion of the Universe is accelerating. This expansion was first discovered in 1929 by American astronomer Edwin Hubble.
The expansion of the Universe was thought to be slowing down because of the gravitational attraction of matter. Astronomers were thus very surprised to discover this was not the case at all.
In recent years, cosmological observations have supported that the Universe is made of about 25 % of matter and 75 % of dark energy. Unlike matter, which dilutes with expansion, dark energy appears to stay roughly constant.
The new results, to be published by the SuperNova Legacy Survey team, put strong constraints on the absence of dilution of dark energy.
It is hoped that, by the end of 2008, when the project would have been finalized, the researchers will have a better understanding on the physical nature of this cosmological constant.