Launch of a satellite to better understand the Universe

Launch of a satellite to better understand the Universe
Launch of a satellite to better understand the Universe

It is a symbol of France-China space cooperation: the Asian giant is launching a satellite on Saturday responsible for spotting “gamma bursts”, real luminous fossils which should provide more information on the history of the Universe.

Developed by engineers from the two countries, this mission called “Svom” (Space-based multi-band astronomical Variable Objects Monitor), a notable Sino-Western collaboration in space, aims to detect and locate these very distant cosmic phenomena, monumental power.

The 930 kilo satellite and its four instruments (two Chinese, two French) will fly aboard a Chinese Long March 2-C rocket from the Xichang space base, in Sichuan province (southwest China). ).

But what is a gamma burst? To simplify, they usually occur after the explosion of massive stars (more than 20 times the mass of the sun) or the merger of compact stars. The most powerful explosions in the Universe, these colossally bright bursts of radiation can release energy equivalent to more than a billion billion suns.

Why, above all, are these gamma-ray bursts interesting? “Observing them is a bit like going back in time, because their light takes a long time to reach us on Earth, several billion years for the most distant ones,” explains Frédéric Daigne, astrophysicist at the Institute of Astrophysics of Paris and one of the main French experts on gamma-ray bursts.

As it travels through space, this light also passes through different gases and galaxies, taking their imprints with it. Valuable information to better understand the history and evolution of the Universe. “We are also interested in gamma-ray bursts for their own sake, because they are very extreme cosmic explosions which allow us to better understand the death of certain stars,” notes Daigne.

The most distant burst identified so far occurred just 630 million years after the Big Bang – or 5% of the current age of the Universe.

“All of this data also makes it possible to test the laws of physics with phenomena that are impossible to reproduce in the laboratory on Earth,” emphasizes Frédéric Daigne. Once analyzed, this information can also be used to better understand the composition of space, gas dynamics and other galaxies.

The satellite, placed in Earth orbit at an altitude of 625 km, will send its precious data to observatories on Earth. Main difficulty: the extreme brevity of gamma-ray bursts will put scientists in a race against time to collect information.

As soon as Svom detects a burst, it will send an alert to a team on call 24 hours a day. In less than five minutes, they will then have to trigger a network of telescopes on the ground which will align themselves precisely in the axis of the source of the burst, for more in-depth observations.

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