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The European Space Agency’s €1.4 billion space telescope is on a mission to map billions of galaxies across the universe, helping scientists understand the mysterious “dark energy” and “dark matter” thought to dominate the universe.
The Euclid Observatory blasted off on schedule Saturday toward its observation point 1.5 million kilometers from Earth on a Falcon 9 rocket built by Elon Musk’s SpaceX. The success of the key moments of the launch from Cape Canaveral in Florida was greeted with applause – in particular when the two-ton satellite sent an independent signal to the control room after separating from the rocket’s last stage.
Emotional, ESA’s science director Carol Mundell said, “It’s hard to find words to describe my feelings. This mission has been in the making for 15 years. (It’s) the next six years will reveal the secrets of the dark universe.”
The agreed view among cosmologists is that all visible matter known to scientists, from galaxies to subatomic particles, accounts for only 5 percent of the mass and energy in the entire universe.
Dark energy, which makes up 70 percent, seems to be a property of space itself, which is expanding the universe at an ever-increasing rate. Contradicting this is the gravitational pull of dark matter, which accounts for 25 percent and has mass but no other measurable properties.
“There are hundreds of models of what dark matter and dark energy could be, but we have no idea that might reflect reality,” said Adam Amara, director of the University of Portsmouth’s Institute of Cosmology and Gravity.
In 2005 a small group of us proposed a space telescope to explore the dark universe. And now, nearly 3,000 people have worked together to make that dream a reality.
Euclid—named after the ancient Greek mathematician considered the father of engineering—was originally destined to be launched on a Russian Soyuz rocket, but the plan fell victim to a rupture in relations in the wake of the all-out invasion of Ukraine.
The European Space Agency turned instead to SpaceX and the Falcon 9. Finding a different launcher and reconfiguring the spacecraft delayed the mission by no more than a year.
In about a month, Euclid will reach its destination, the “second Lagrangian point” 1.5 million kilometers away. Gravity from the Sun and Earth perfectly balances the orbital motion of the satellite, so it appears to be hovering in the same place in space. The James Webb Space Telescope is located nearby.
There you’ll map the universe by observing galaxies 10 billion light-years away across the 36 percent of the sky unobscured by stars and dust in Earth’s own Milky Way.
“We will be able to reconstruct the cosmological history of the universe over the past 10 billion years,” said Euclid Consortium Yannick Méliès of the Astrophysical Institute in Paris.
Changes in the motion and distribution of galaxies and the way they clump together will reveal the influence of the dark universe. Dark matter tends to hold galaxies together through the force of gravity, while dark energy pushes them apart as it speeds up the expansion of the universe.
Two cameras are attached to the 1.2-meter Euclid telescope. The first, led by British scientists, records in visible light. The other, led by French researchers, operates in the near infrared spectrum.
Mark Cropper of University College London has led the design and development of the visual camera for 16 years.
“The instrument will image a large swath of the distant universe with nearly the exact resolution of the Hubble Space Telescope, observing more of the universe in one day than Hubble has done in 25 years,” he said. “The universe has never been seen on this scale, in this level of detail.”
Whether it’s an intrinsic property of empty space, a “vacuum energy” of virtual particles as predicted by some quantum physicists or a previously unknown energy field, scientists hope telescope images will help define dark energy. Their findings could provide evidence for a fundamental revision of Einstein’s theory of gravity.
Possible explanations for dark matter vary equally, Amara said. Candidates range from tiny particles that interact with ordinary matter only through the force of gravity, to black holes formed shortly after the Big Bang that still roam the universe.
Amara doesn’t think dark matter has a simple explanation. “If you think about all the ordinary matter in the universe,” he said, “it takes on phenomenally rich and complex forms.” “There could be an equally diverse universe of dark matter out there.”