- 4631
- DARK ENERGY
- new ways to study it? “Dark Energy Spectroscopic Instrument”
(DESI). Each of its 5,000 robotic
positioners are precisely pointing to their celestial targets to within a tenth
of the width of a human hair. The
corrector barrel holds DESI’s six large lenses in precise alignment.
-
---------------------------------------- 4631
- DARK
ENERGY - new ways to study it?
-
- The hexapod, designed and built with
partners in Italy, focuses the DESI images by moving the barrel-lens system.
Both the barrel and hexapod are housed in the cage, which provides the
attachment to the telescope structure.
-
- Charge-coupled devices, or CCD convert the
light passing through the lenses from distant galaxies into digital
information. A complex analysis of
DESI’s first year of data provides one of the most stringent tests yet of
general relativity and how gravity behaves at cosmic scales
-
- Looking at galaxies and how they cluster
across time reveals the growth of cosmic structure, which lets DESI test
theories of modified gravity which is an alternative explanation for our
universe’s accelerating expansion
-
- DESI researchers found that the way
galaxies cluster is consistent with our standard model of gravity and the
predictions from Einstein’s theory of general relativity. Gravity has shaped our cosmos. Its
attractive influence turned tiny differences in the amount of matter present in
the early universe into the sprawling strands of galaxies we see today.
-
- Using data from the “Dark Energy
Spectroscopic Instrument” (DESI) has traced how this cosmic structure grew over
the past 11 billion years, providing the most precise test to date of gravity
at very large scales.
-
- The result validates our leading model of
the universe and limits possible theories of modified gravity, which have been
proposed as alternative ways to explain unexpected observations including the
accelerating expansion of our universe that is typically attributed to dark
energy.
-
- The study also provided new upper limits on
the mass of neutrinos, the only fundamental particles whose masses have not yet
been precisely measured. Previous neutrino experiments found that the sum of
the masses of the three types of neutrinos should be at least 0.059 eV/c^2.
(For comparison, an electron has a mass of about 511,000 eV/c^2.) DESI’s results indicate that the sum should
be less than 0.071 eV/c^2, leaving a narrow window for neutrino masses.
-
- The complex analysis used nearly 6 million galaxies
and quasars lets researchers see up to 11 billion years into the past. With
just one year of data, DESI has made the most precise overall measurement of
the growth of structure, surpassing previous efforts that took decades to make.
-
- DESI’s first year of data made the largest
3D map of our universe to date and revealed hints that dark energy might be
evolving over time. The results looked at a particular feature of how galaxies
cluster known as “baryon acoustic oscillations” (BAO).
-
- The new analysis, called a “full-shape
analysis,” broadens the scope to extract more information from the data,
measuring how galaxies and matter are distributed on different scales
throughout space.
-
- DESI is a state-of-the-art instrument that
can capture light from 5,000 galaxies simultaneously. DESI sits atop the U.S. National Science
Foundation’s Nicholas U. Mayall
4-meter Telescope at Kitt Peak National Observatory . The experiment is
now in its fourth of five years surveying the sky and plans to collect roughly
40 million galaxies and quasars by the time the project ends.
-
- The collaboration is currently analyzing
the first three years of collected data and expects to present updated
measurements of dark energy and the expansion history of our universe in spring
2025.
-
- Dark matter makes up about a quarter of the
universe, and dark energy makes up another 70 percent, and we don’t really know
what either one is. The idea that we
can take pictures of the universe and tackle these big, fundamental questions
is mind-blowing
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December 2, 2024 DARK ENERGY
- new ways to study it? 4631
------------------------------------------------------------------------------------------
-------- Comments appreciated and Pass it on to
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--- Some reviews are at: -------------- http://jdetrick.blogspot.com -----
-- email feedback, corrections, request for
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--- to:
------
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------ “Jim Detrick” -----------
--------------------- --- Tuesday, December 3,
2024
---------------------------------
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