Astronomers have summed up the results of the first seven months of observations as part of a survey of the sky by the DESI spectrograph. They built a new 3D map of the distribution of galaxies in the universe, covering more than a third of the celestial sphere, which is the largest and most detailed map of its kind to date.
Dark Energy Spectroscopic Instrument (DESI)
The creation of the DESI tool (Dark Energy Spectroscopic Instrument) began in 2015, and the device saw its first light at the end of 2019. It is mounted on the 4-meter Mayall Telescope at the Kitt Peak National Observatory in Arizona.
The main goal of DESI is to conduct a five-year large-scale program of spectroscopic studies in the optical range of millions of distant galaxies and quasars, which will allow the creation of three-dimensional detailed maps of the distribution of matter in the Universe.
Thanks to this, astronomers hope to understand the nature of dark energy and determine the rate of expansion of the Universe at different moments of its existence.
The largest 3D map of the universe
A team of astronomers working with DESI, led by Julien Guy at the Lawrence Berkeley National Laboratory, presented the results of the first seven months of observations. They built a new three-dimensional map of the distribution of galaxies in the universe, covering more than a third of the celestial sphere, which is the largest and most detailed map of its kind to date.
As part of the survey, more than 7.5 million galaxies were cataloged, for which redshifts were determined, and new quasars were discovered. The most distant quasar detected by DESI has a redshift value of z=6.53, which means that it existed less than a billion years after the Big Bang. By 2026, the DESI catalog is expected to have over 35 million galaxies and 2.4 million quasars.
Astronomers built a map of the young Universe in 2018
In previous research, a different group of astronomers built one of the largest maps of the young Universe, showing the number of galaxies at different stages of its existence. Scientists looked at the time period from 11 to 13 billion years ago and found about four thousand early galaxies, many of which should have become similar to the Milky Way over time.
Astronomers looked for sources of Lyman-alpha radiation in the COSMOS region of the sky, which was previously surveyed by Hubble. The scientists used images from the Wide Field Camera on the Isaac Newton Telescope and the Suprime-Cam camera on the Subaru telescope, obtained by applying 16 narrow-band and mid-band filters.
This allowed them to select galaxies emitting at certain wavelengths and dating back to a period when the age of the universe was 7-20 percent of the current age (z=2-6).
It turned out that in early galaxies, peculiar bursts of star formation often occurred – this process was less uniform than in our galaxy. In addition, scientists have found in them a population of young stars, which differ from modern ones in lower metallicity, higher temperature, and more blue color.
The researchers also found that ancient galaxies were incredibly compact – basically, their diameter did not exceed three thousand light-years, while for the Milky Way this value reaches 100 thousand light-years. According to scientists, their small size may explain many of the physical phenomena that occurred in the early universe.
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Sources:
• Becker, A. (2022, January 13). Desi creates largest 3D map of the cosmos.
• Metcalfe, T. (2022, January 13). Largest dark energy map could reveal the fate of the universe. LiveScience.
• Nield, D. (n.d.). Take a look at the largest and most detailed 3D map of the universe ever made. ScienceAlert.
• Paulino-Afonso, A., Sobral, D., Ribeiro, B., Matthee, J., Santos, S., Calhau, J., Forshaw, A., Johnson, A., Merrick, J., Pérez, S., & Sheldon, O. (2018, March 8). On the UV compactness and morphologies of typical Lyman-a emitters from Z~2 to Z~6. arXiv.org.
• Young, M. (2022, January 14). Astronomy in pictures: Largest 3D map of our universe and a stellar intruder. Sky & Telescope.
