- 4031 - LARGEST
GALAXY? A new image from the
Hubble Space Telescope gazes into the lair of a monstrous cluster of galaxies
located nine billion light-years away in the constellation Draco.
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4031 - LARGEST
GALAXY?
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- This celestial
galaxy can be seen by the ripples around it. This leviathan is so titanic,
however, that the ripples aren't traveling the surface of an ocean or lake but
rather are distortions in the fabric of space-time itself.
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- This particular
galaxy cluster, “eMACS J1823.1+7822,” is
one of five selected for observation by Hubble astronomers to determine the
strength of this "warping" effect, which was first predicted by
Albert Einstein's theory of general relativity.
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- The 1915 theory,
called Einstein's geometric theory of gravity, predicts that, as bowling balls
placed on a trampoline create a depression, objects with mass cause the very
fabric of space-time to warp. This curvature gives rise to the force of
gravity. And the greater the mass of a cosmic object, the more extreme the
warping of space it causes.
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- Light travels
across the universe in straight lines, but when it encounters a warp caused by
a truly massive object, its path is curved. When the warping object is between
Earth and a background object, it can curve light in such a way that the
apparent position of the background object is shifted.
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- But when the
intermediate or "lensing object" is truly massive, like a monstrous
cluster of galaxies, light from the
background source takes a different amount of time to reach Earth depending on
how close it passes to the natural cosmic lens.
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- This effect, called
“gravitational lensing”, can make single objects appear at multiple points in
the sky, often in stunning arrangements called Einstein rings and Einstein
crosses. It can also cause background objects to appear amplified in the sky, a
powerful effect that astronomers use to observe distant and early faint
galaxies.
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- The distortion
caused by a massive clusters can also
help astronomers study mysterious dark matter, which accounts for around 85% of
the mass in the universe but is invisible because it does not interact with
electromagnetic radiation. Because dark matter does interact gravitationally,
however, the lensing of light by a galaxy or galactic cluster can help
researchers map the distribution of dark matter.
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- The galaxy
cluster warps the shape of the galaxies around it, giving them a slightly
elongated shape, turning some into arcs and others into bright streaks. Hubble's Advanced Camera for Surveys and its
Wide Field Camera 3 instrument, both of which have the ability to view galaxies
and stars in specific wavelengths of light. Observing objects at different
wavelengths in this way allows for a more complete picture of the structure.
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- Such observations
can reveal the composition and behavior of an object that would be hidden in
visible light alone. When combined with the use of clusters like eMACS
J1823.1+7822, gravitational lensing allows this to be done for some of the
universe's earliest galaxies.
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- Powerful
observatories like Hubble and the James Webb Space Telescope can probe
conditions found shortly after the Big Bang and the very birth of the universe.
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May 31, 2023 LARGEST GALAXIES
4031
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------ “Jim Detrick” -----------
--------------------- --- Thursday, June 1, 2023
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