- 3669 - DARK ENERGY - the James Webb survey? - Because light from a background object can take different paths past a massive object like a galaxy gravitational lensing can make the source appear distorted, magnified or even in multiple places in the sky. It was gravitational lensing that smeared distant galaxies in the first image from the James Webb Space Telescope.
--------------------- 3669 - DARK ENERGY - the James Webb survey?
- New research could help scientists use gravitational lensing, the warping of light from distant galaxies, to investigate the accelerating expansion of the universe. Scientists are still coming up empty in the hunt for flaws in Einstein's theory of general relativity that could explain the mysterious force driving the accelerating expansion of the universe, called Dark Energy.
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- The researchers studied 100 million galaxies looking for signs that the strength of gravity has varied throughout the universe's history or over vast cosmic distances. Any sign of such a change would indicate that Einstein's theory of general relativity is incomplete or in need of revision. Variation could also shed light on what dark energy is, beyond that it's the name scientists give to whatever is causing the expansion of the universe to accelerate.
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- Despite finding no such variations in gravity's strength, the work will help two forthcoming space telescopes, the European Space Agency's Euclid mission and NASA's Nancy Grace Roman Space Telescope, also hunt for changes in the strength of gravity through space and back through time.
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- Scientists' think that the universe's expansion should be slowing after the initial push of the Big Bang. But it isn't. It's accelerating, and the term "dark energy" is a name given for the mysterious force driving this acceleration.
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- As a result, dark energy is, in effect, working against the force of gravity, pushing cosmic objects apart as gravity draws them together. And, dark energy accounts for around 68% of the universe's energy and matter content.
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- Light travels at a constant speed, meaning that astronomers see distant cosmic objects as they were in the past. For example, light takes roughly seven minutes to travel from the sun to Earth, so from our planet we see our star as it was seven minutes ago.
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- When astronomers look at a Milky Way object one light-year away, they see as it was a year ago. And for some of the distant galaxies that the James Webb Telescope is studying, light has been traveling to us for tens of billions of years and we see the galaxies as they were when the 13.8 billion-year-old universe was in its relative infancy.
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- It isn't the observations of the galaxies themselves that could hint at changes in the strength of gravity, however, but rather what has happened to their light during its long journey.
- According to general relativity, mass curves the very fabric of spacetime, with objects of greater mass causing more extreme curvature. Objects like galaxies warp spacetime so strongly that as light passes a galaxy, its path is curved. When this light reaches Earth, the object that emitted it shifts in apparent position in the sky. Astronomers call the effect “gravitational lensing“.
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- Light from a background object can take different paths past a massive object like a galaxy gravitational lensing can make the source appear distorted, magnified or even in multiple places in the sky. Gravitational lensing smears distant galaxies in the images from the James Webb Space Telescope.
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- The effects of gravitational lensing can be more subtle, however, and these subtle effects are often caused by dark matter in the lensing object. And because dark matter interacts only with gravity, ignoring light and other matter altogether, its shape and structure are caused by this force alone.
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- The Dark Energy Survey scientists looked for these subtle distortions, called 'weak gravitational lensing,' in images of distant galaxies. The researchers reasoned that this would reveal changes in the distribution of dark matter in lensing galaxies, which would in turn hint at changes in the strength of gravity over time and space.
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- However, observations of the shape of dark matter in 100 million galaxies showed everything still in keeping with Einstein's general relativity. Astronomers are turning to the “Euclid and Roman space telescopes“, set to launch in 2023 and 2027, to search for these variations in gravity in galaxies that are still more ancient, hoping to spot changes that may set a course toward the understanding of dark energy.
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- While this new study looked at galaxies as they were 5 billion years ago, Euclid will look back 8 billion years, and Roman will look back even further, observing galaxies as they were 11 billion years ago.
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- Stay in school there is much more to learn!
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August 31, 2022 DARK ENERGY - the James Webb survey? 3669
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