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Astronomers are predicting an “avalanche of discoveries” after the first major release of observations from a European space telescope built to study the mysterious dark matter and dark energy that comprise the bulk of the universe. The European Space Agency’s Euclid mission has captured images of 26m galaxies, covering 10bn years of cosmic history. They give researchers unprecedented insight into the forces that shape the cosmos and the galaxies it holds.
The first batch of survey data has allowed researchers to create a detailed catalogue of 380,000 galaxies, revealing the rich variation in galactic structures, with some caught in the act of merging with their neighbours. Further images reveal how massive galaxies surrounded by dark matter, the invisible substance said to pervade the universe, warp space and magnify more distant galaxies behind them. These rare images are among the best leads scientists have for understanding the nature of dark matter.
Three years before publishing his general theory of relativity in 1915, Albert Einstein predicted that strong gravitational fields generated by massive objects such as galaxies would warp space-time. Astronomers call the effect gravitational lensing, because the warping behaves like a lens, magnifying more distant objects. Observations from Euclid gathered over a single week captured 500 strong gravitational lensing events where the warping of space-time is clearly visible. When a background galaxy is magnified by lensing it often appears as a bright arc around the border of the foreground galaxy.
“We have precious few clues as to what dark matter is,” said Stephen Serjeant, a professor of astronomy at the Open University. “But one of the ways we might figure out what dark matter is, is how it clumps.” The rarest, but most valuable images have a foreground galaxy that bends light from multiple galaxies behind it. With Euclid, researchers hope to massively increase the number of such images.
“This is the significance of our strong gravitational lenses,” said Serjeant. “It’s the start of an avalanche of new discoveries, and among this avalanche will be beautiful clues about what dark matter is made of.” The most popular theory of the universe suggests only 5% is made from ordinary matter. Dark matter, an invisible substance that forms what is called the cosmic web, is said to account for 25%. The bulk, about 70%, is said to be dark energy, a mysterious force that is accelerating the expansion of the universe.
Euclid is expected to capture images of more than 1.5bn galaxies over six years. Detailed measurements of these will reveal how dark energy is driving the expansion of the universe.
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Fascinating details in your excerpt.
A recent explanation of gravity I’ve come across. I’ll use our planet as an example. (A) Like all objects the earth tries to move in a straight line. (B) Due to the curvature of space caused by dark matter, it can’t do that. (C) What we on earth feel as gravity is actually the planet veering off path due to that curvature. Think of it as racing around a sharp curve in a sports car at 150 MPH. occupants are pressed against one side of the vehicle. That’s the most recent explanation of gravity I’ve come across. Dunno. Makes some sense. But in some ways it doesn’t. Gravity is one of the most mysterious forces scientists face.
Yeah - Gravitational lensing has been known about / used by astronomers for several decades. But taken to a higher level by the new telescopes.
”One profound result of Einstein’s theory of general relativity: gravity bends the path of light, much as it affects the path of massive objects. Very massive astronomical bodies, such as galaxies and galaxy clusters, can magnify the light from more distant objects, letting astronomers observe objects that would ordinarily be too far to see. Even the gravity from planets affects light, allowing researchers to detect worlds in orbit around other stars. This effect is called “gravitational lensing”, and it’s used to discover faint astronomical objects and to study the “lenses” themselves through their gravitational effects.”
”When light from a distant galaxy passes by a massive galaxy or galaxy cluster closer to Earth, gravity bends the path of the light. Since the source galaxy emits light in all directions, many of those paths can converge on us, focusing the light. That makes the source galaxy appear brighter than it would ordinarily appear from Earth, to the point where gravitational lensing can let us see objects too faint to observe otherwise. This “strong lensing” effect makes gravity act as a telescope.”