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 (±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%.

Background

• 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.