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DESI observes the night sky. The Rochester Group has been participating in DESI since 2017 and members have played a key role in the commissioning and operation of the equipment. Credit: KPNO/NOIRLab/NSF/AURA/T.slovinski
Scientists have analyzed the first batch of data from the dark energy spectrometer's quest to map the universe and unravel the mysteries of dark energy.
Using the Dark Energy Spectroscopy Instrument (DESI), a mountaintop telescope equipped with 5,000 small robots, researchers can peer 11 billion years into the past. Light from distant objects in space is just now reaching DESI, allowing scientists to map the universe in its youth while tracking its growth. Understanding how the universe evolved is tied to one of the biggest mysteries in physics: dark energy, which researchers hypothesize is driving the expansion of the universe. It is standing.
DESI is an international scientific collaboration involving over 800 scientists from around the world. Among them are researchers from the University of Rochester's cosmology group. This group is an interdisciplinary group that includes professors, postdocs, graduate students, and undergraduate students in physics, astronomy, data science, and computer science. The group is co-led by physics professor Regina Demina. Segev BenZvi, Associate Professor of Physics. and Kelly Douglas, assistant professor of physics and astronomy (education).
DESI is currently in the midst of a five-year quest to measure 40 million galaxies and quasars and create the largest 3D map of the universe ever constructed, using the most accurate measurements to date. . The instrument began research in 2021, and researchers recently published an analysis of data collected during the first year, including measurements of the universe's expansion rate and composition. They published their analysis in multiple papers. arXiv Preprint server.
“DESI data is a significant increase in size over data we have previously collected,” Douglas said. “DESI's sample of galaxies and quasars in its first year is six times larger than the combined measurements of all spectroscopic surveys conducted over the past 40 years.”
And Demina adds that the first year's data is just the beginning. “The complete data set will allow us to take a closer look at the early days of the universe, a time when the universe underwent rapid exponential expansion.”
optical eyes in the sky
The DESI instrument is located in the refurbished Mayall telescope at the National Science Foundation's Kitt Peak National Observatory near Tucson, Arizona. The instrument incorporates optics that expand the telescope's field of view, collects spectroscopic data from objects within the telescope's field of view, and is robotically controlled to investigate the three-dimensional location of galaxies and quasars in the universe. Contains 5,000 optical fibers.
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Zach Brown, a doctoral student at the University of Rochester, completed his work at the Kitt Peak National Observatory in Arizona in October 2023. The DESI instrument (cylindrical black instrument) is attached to the refurbished Mayall telescope at Kitt Peak.Credit: Ann Elliott, Ohio State University
The Rochester Group has been participating in DESI since 2017. Group members played a key role in commissioning and operating the equipment, including developing and troubleshooting software to ensure the 5,000 fibers were optimally directed to their targets.
Members of the Rochester group will conduct a year-long project to better ensure the accuracy and reliability of their results, including studying systematic uncertainties (potential errors and variations) that can affect measurements. He also made a major contribution to the verification of eye data.
Deciphering the expansion of the universe and dark energy
DESI was built to measure baryon acoustic oscillations (BAOs), giant bubble-like structures formed by conditions immediately after the Big Bang and followed by galaxies. In DESI's first year, he used spectroscopic samples of 5.7 million galaxies and quasars to measure the size of the BAO and estimate the rate of expansion of the universe, known as the Hubble constant.
BAO is also used to limit the density of dark matter and dark energy. Scientists had long believed that the universe was expanding at a constant rate, but in 1999 they discovered that the rate of expansion was accelerating. Dark energy is hypothesized to be causing the acceleration.
Some theories suggest that dark energy is contributed by one or more scalar fields (an invisible force that expands the universe), similar to the scalar fields that were hypothesized to cause the inflationary growth of the universe shortly after the Big Bang. It suggests that there is.
“So far, the Higgs field is the only scalar field known to humanity,” said Demina, who was part of the team that discovered the Higgs field in 2012 using the Large Hadron Collider at CERN in Switzerland. To tell. “Now is the time to see if there are more areas like that.”
Another question that DESI seeks to answer is whether dark energy has a constant value everywhere in the universe (known as the cosmological constant), or whether its properties differ in time and space. His BAO measurements from his first year at DESI are consistent with a cosmological constant, but slightly favor models that suggest dark energy is an evolving, or “dynamic” field.
According to BenZvi, “Evidence supporting the evolution of dark energy could be very interesting, but it could also be a random fluctuation. We won't know until we see the next batch of data. The current Estimated next release in late 2025.”
For more information:
DESI paper: data.desi.lbl.gov/doc/papers/
Magazine information:
arXiv