- 4087 - DESI - new astronomical discoveries? DESI collects spectra, the different frequencies of l-ight that objects in space emit. That light tells researchers how far away the object is, meaning they can create a 3D map of the universe.
--------------------- 4087 - DESI - new astronomical discoveries?
- DESI has software
that ensures that each of the 5,000 robotic positioners are precisely pointing
to their celestial targets to within a 10th of the width of a human hair.
-
- The corrector
barrel holds DESI’s six large lenses in precise alignment. 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.
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- The
charge-coupled devices, or CCDs convert the light passing through the lenses
from distant galaxies into digital information that can then be analyzed by the
collaboration.
-
- The universe is
big, and it’s getting bigger. To study dark energy, the mysterious force behind
the accelerating expansion of our universe, scientists are using the Dark
Energy Spectroscopic Instrument (DESI) to map more than 40 million galaxies,
quasars, and stars.
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- The 80-terabyte
data set just released comes from 2,480 exposures taken over six months during
the experiment’s “survey validation” phase in 2020 and 2021. The Dark Energy Spectroscopic Instrument
sits atop the Mayall 4-Meter Telescope at Kitt Peak National Observatory.
-
- The DESI data will
not only allow the study of dark energy but will also be coveted by the whole
scientific community to address other topics, such as dark matter,
gravitational lensing, and galactic morphology.
-
- DESI uses 5,000
robotic positioners to move optical fibers that capture light from objects
millions or billions of light-years away. It is the most powerful multi-object
survey spectrograph in the world, able to measure light from more than 100,000
galaxies in one night. That light tells researchers how far away an object is,
building a 3D cosmic map.
-
- DESI’s survey
validation included the “One-Percent Survey” visualized in this flythrough.
Researchers took detailed images in 20 different directions on the sky,
creating a 3D map of 700,000 objects and covering roughly 1% of the total
volume DESI will study. With the instrument and survey plan successfully
tested, the main DESI survey is now filling in the gaps between those observations.
-
- As the universe
expands, it stretches light’s wavelength, making it redder, known as redshift.
The further away the galaxy, the bigger the redshift. DESI specializes in
collecting redshifts that can then be used to solve some of astrophysics’
biggest puzzles: what dark energy is and how it has changed throughout the
universe’s history.
-
- While DESI’s
primary goal is understanding dark energy, much of the data can also be used in
other astronomical studies. Two
interesting finds have already surfaced incude evidence of a mass migration of
stars into the Andromeda galaxy, and incredibly distant quasars, the extremely
bright and active supermassive black holes sometimes found at the center of
galaxies.
-
- Those high-redshift
quasars are usually found with very large telescopes, so the fact that DESI, a
smaller, 4-meter survey instrument, could compete with those larger, dedicated
observatories demonstrates the exceptional throughput of the instrument.
-
- DESI uses 5,000
fiber-optic “eyes” to rapidly collect light from distant galaxies. In good
observing conditions, the experiment can image a new set of 5,000 objects every
20 minutes. Raw data from DESI’s ten spectrometers (which split a galaxy’s
light into different colors) is transformed into useful information.
-
- If you looked at
them, the images coming directly from the camera would look like nonsense –
like lines on a weird, fuzzy image. The
magic happens in the processing and the software being able to decode the
data. All of the experiment’s code,
including the computational heavy lifting, is written in the programming
language Python rather than the traditional C++ or Fortran.
-
- DESI is currently
two years into its five-year run and ahead of schedule on its quest to collect
more than 40 million redshifts. The survey has already catalogued more than 26
million astronomical objects in its science run, and is adding more than a
million per month.
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-
July 11, 2023 DESI
- new astronomical
discoveries 4087
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