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EI2GYB > ASTRO 30.08.21 14:12l 89 Lines 4218 Bytes #999 (0) @ WW
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Subj: Hubble captures an 'Einstein Ring'
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Hubble captures an 'Einstein Ring'
A new photograph from the Hubble Space Telescope shows a stunning
"Einstein Ring" billions of light-years from Earth - a phenomenon named
after Albert Einstein, who predicted that gravity could bend light.
The round object at the center of the photograph released by the European
Space Agency is actually three galaxies that appear as seven, with four
separate images of the most distant galaxies forming a visible ring around
the others.
The farthest galaxy - a special type of very bright galaxy with a gigantic
black hole at its center, known as a quasar - is about 15 billion light-years
from Earth.
At such a great distance, it should be invisible to even the best space
telescopes, but its light is curved by the two galaxies in front, about
3 billion light-years away, so its image appears to us in five separate
places: four times in the ring and once at the center of the ring,
although that can be detected only in the telescope's numerical data.
The rare phenomenon is named after Einstein, the physicist who predicted in
1911 that gravity would affect light just as it affects physical matter.
Einstein proposed the idea as a test of his theory of general relativity
in 1915, and in 1919 the British astronomer Arthur Eddington confirmed
the effect during a solar eclipse on the island of Principe off the west
coast of Africa, noting that stars near the eclipsed disk appeared
fractionally out of place because their light was being bent by the sun's
gravity.
Telescopes in Einstein's time weren't able to detect any other signs of
the phenomenon.
It was seen first by astronomers at the Kitt Peak Observatory in Arizona
in 1979 as Twin Quasar QSO 0957+561, a single quasar that looks like two
here on Earth because its image is "gravitationally lensed" by a closer
but unseen galaxy.
Since then, astronomers have discovered hundreds of Einstein Rings -
the alignment of the distant galaxies needs to be perfect, and none can
be seen without a large telescope.
A common formation is the Einstein Cross, in which a distant galaxy appears
as four separate images around a galaxy closer to Earth but the closer
galaxy is too dim to be seen.
Einstein Rings and Einstein Crosses are more than just pretty phenomena -
gravitational lensing allows astronomers to look much farther into the
depths of the universe, and it reveals otherwise hidden details of the
galaxies that cause the lensing.
"The Einstein Rings and Einstein Crosses are presumably evidence of more
material in the closer galaxies than meets the eye, and that most likely
means dark matter," said the astronomer Ed Krupp, the director of the
Griffith Observatory in Los Angeles.
Their distribution can "help illuminate the identity and distribution
of dark matter and the relativistic geometry of the whole universe."
Such gravitational lenses have also spotted some of the most distant
dwarf galaxies in the universe, which, being among the oldest, can
tell astronomers more about galaxy formation, while gravitational
"microlensing" - variations in the light from individual stars - has
revealed the unseen presence of distant exoplanets, Krupp said in an email.
Photos can be found at:
https://www.nbcnews.com/science/space/hubble-captures-einstein-ring-rcna1753
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