The European space telescope Euclid is scheduled to launch on Saturday to try to shed light on one of the greatest scientific mysteries: dark matter and dark energy, which make up 95% of the universe but about which we know almost nothing.
The satellite is scheduled to launch at 11:12 a.m. local time (15:12 GMT) aboard a SpaceX Falcon 9 rocket in Cape Canaveral, Florida.
The two-ton telescope will be placed 1.5 million kilometers from Earth.
Euclid, named for the father of geometry, “will be the first space mission to study the properties of dark energy,” said Michael Seiffert, the project’s science director for NASA, which is participating in the mission. the European Space Agency (ESA).
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Over a period of six years, the probe will create a three-dimensional map of the Universe covering about two billion galaxies over part of a third of the celestial sphere. The observed distant galaxies will allow a journey back in time 10 billion years ago – to the time it took their light to reach us.
The immense amount of data collected is made public for the scientific community to use, followed by around 2,600 researchers who are members of the Euclid Consortium from around fifteen countries.
opposing forces
Dark matter (25% of the universe) and dark energy (70%) have opposite effects: when the first exerts a gravitational pull that holds cosmic objects together, dark energy causes them to disintegrate.
As for dark matter, we know that it exists because of a mysterious observation: it’s impossible to explain how a galaxy or a group of galaxies doesn’t disintegrate just by looking at the gravity of its visible elements (planets, stars, etc.) taken into account. ).
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“You have to start from an additional amount of matter that is invisible to our telescopes, like a gravitational component that holds everything together,” says Michael Seiffert.
This cosmic “cement” is called dark matter.
According to certain hypotheses, these could be subatomic particles that have never been observed directly.
Dark energy is perhaps even more mysterious.
We have known that the universe is expanding since the discoveries of the famous astronomer Edwin Hubble in the 1920s. And since the 1990s, this expansion has accelerated.
However, this “implies that on very large scales, gravity actually contains a repulsive component that tears things apart,” says Seiffert. This force is dark energy, “a great mystery of physics.”
3D map
The head of the Euclid mission at ESA, Giuseppe Racca, described the lack of knowledge about these two dark components as an “embarrassing situation”.
However, the satellite does not aim to determine their nature (too ambitious), but first to better understand their characteristics, the way they act and evolve over time.
Thanks to its 3D map, the telescope will allow precise measurements of galaxy distribution and the extent of the Universe.
Giuseppe Racca explained that dark matter and dark energy are “indirectly” inferred from these observations. The calculation of dark matter can be done by “subtracting” the visible matter.
For dark energy, David Elbaz, an astrophysicist at the Atomic Energy Commission (CEA) and a member of the Euclid Collaboration, draws the parallel to a balloon: dark energy is the breath that inflates the balloon. So it will be instructive to watch how it grows.
The acceleration of the expansion of the universe would have started six billion years ago. 10 billion years ago, Euclid saw the first effects of dark energy.
fate of the universe
All of this data could also shed light on the fate of the universe. The “big crunch” theory (the universe contracting onto itself) has been weakened since the discovery of the accelerated expansion of the universe.
But how it continues to expand — perhaps in tens of billions of years, until it pushes planets away from the Sun or even tears atoms apart — will depend on the properties of dark energy, which Euclid needs to help measure, Michael Seiffert points out.
The telescope has two instruments on board: a visible light imager (VIS) and a near-infrared spectroimager (NISP).
The antenna only has to be used in flight and should be operational after about three months.
At a cost of 1.5 billion euros, the European mission must last at least until 2029.
NASA also plans to launch a mission to study dark matter in a few years: the Roman Nancy Grace Space Telescope.