A groundbreaking study has emerged, challenging existing theories by suggesting that dark energy, the force expanding our universe, has weakened since 4.5 billion years ago.
On Monday, an international research team, which includes scientists from the Korea Astronomy and Space Science Institute, announced their findings based on three years of data encompassing roughly 15 million galaxies and quasars. Their analysis indicates a decrease in dark energy density.
The Dark Energy Spectroscopic Instrument (DESI) is a massive international collaboration project to create a 3D universe map to unravel the mystery of dark energy, which makes up 70% of the universe’s energy. This project uses a multi-channel spectrometer with 5,000 fiber-optic robots perched atop Kitt Peak in Arizona. About 900 researchers from 11 countries, including Korea, participated in the project.
Dark energy speeds up the expansion of the universe. According to the standard cosmological model, which explains its history, dark energy is treated as a constant, unchanging force.
However, new research suggests that dark energy’s density has decreased by 10% compared to 4.5 billion years ago. If this analysis holds up, the universe’s expansion is slowing down, so the current standard cosmological model may need to be modified.
DESI studies how matter is spread across the universe to track dark energy’s influence. It analyzes explicitly baryon acoustic oscillation (BAO) patterns.
BAO is a subtle pattern left in the distribution of matter by early cosmic events. These patterns act like standard rulers, and their size is directly affected by the universe’s expansion.
The team used DESI data, which measured distances using this standard ruler. In addition, they combined observations of cosmic microwave background radiation, supernovae, and weak gravitational lensing for good measure.
The results showed that the observational data combined with the standard cosmological model, Lambda Cold Dark Matter theory (LCDM), do not fit together. Instead, the researchers found that the dark energy model, which changes over time, explains the observations better than the standard cosmological model.
The DESI year 3 data analysis involved about 200 researchers, including Dr. Shafieloo Arman, Dr. David Parkinson, Dr. William Matthewson, and PhD student Kushal Lodha from the Korea Astronomy and Space Science Institute. The institute led one of the key papers, “Expanded Dark Energy Analysis,” with Kushal Lodha as the primary author.
DESI is currently in year four of its five-year mission. By the time it wraps up, it aims to have measured 40 million galaxies and quasars.
Dr. Shafieloo Arman, a professor at UST and core researcher at the Korean Gravitational Wave Group, stated, “This is the beginning of a tremendous discovery that dark energy may not be a cosmological constant. It could completely change our understanding of the standard cosmological model and shake the very foundations of theoretical physics.”