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Dark Energy Spectroscopic Instrument (DESI)

Why is it in the news?

  • Dark Energy Spectroscopic Instrument (DESI) has published research revealing the most precise measurement of the universe’s expansion to date.

Key highlights

  • The expansion rate is determined to be 68.5 (卤0.6) kilometres per second per megaparsec (a million parsec; 1 parsec equals 3.2616 light years).
  • This marks the first time scientists have measured the expansion history of the young universe with a precision better than 1%.


  • The universe’s expansion has been known since Edwin Hubble’s observations in 1929, with recent discoveries showing it’s accelerating.
  • This acceleration led to the hypothesis of ‘dark energy,‘ an invisible force constituting around 70% of the universe.
  • DESI, a project involving over 900 researchers worldwide, aims to study dark energy.
  • DESI operates using 5,000 robotic ‘eyes’ on the Nicholas W Mayall 4-meter Telescope, capturing light from 5,000 galaxies simultaneously.
  • Observations from DESI’s first year have been used to create the most comprehensive 3D map of the universe to date, covering galaxies as far back as 11 billion years.
  • Precise distance measurements from DESI have allowed for the mapping of galaxy distribution and movement over time, revealing the universe’s expansion rate.
  • DESI’s findings suggest discrepancies with current theoretical models, hinting at possible fluctuations in dark energy density.
  • While intriguing, these findings require further confirmation as they currently have around a 95% confidence level.
  • Confirmation of fluctuating dark energy density could revolutionize our understanding of the universe, potentially leading to new physics.
  • The DESI collaboration plans to continue analysing data from subsequent years of observations to further explore the nature of dark energy.
According to the leading model of the universe, Lambda CDM (Cold Dark Matter), both matter and dark energy influence the universe’s expansion, but in opposing ways.

路聽聽聽聽聽聽 Matter and dark matter slow down the expansion, while dark energy accelerates it.

路聽聽聽聽聽聽 Dark Energy constitutes approximately 68% of the universe and is an unknown form of energy driving the accelerated expansion.

路聽聽聽聽聽聽 Dark Matter, comprising about 27% of the universe, is a hypothetical form of matter inferred from its gravitational effects on visible matter and background radiation.


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