A new study by Anowar Jaman Shajib, associate member of the Center for Astronomy, Space Science and Astrophysics (CASSA) at Independent University, Bangladesh (IUB), suggested that dark energy—the mysterious force driving the universe’s accelerated expansion—may not be constant. The findings could reshape our understanding of the universe’s ultimate fate.
The paper, “Scalar field dark energy models: Current and forecast constraints”, was published in Physical Review D on September 8, 2025. Shajib, also an Einstein Fellow at the University of Chicago, co-authored the study with Prof. Joshua A. Frieman, Emeritus Professor at the University of Chicago.
For over two decades, scientists have treated dark energy as a constant, the so-called cosmological constant first proposed by Einstein. But recent astronomical surveys indicate that dark energy may evolve over time, with profound implications for the universe’s future.
- If dark energy strengthens over time, it could eventually tear apart galaxies, atoms, and even space-time itself—a scenario known as the Big Rip.
- If it weakens, cosmic expansion could halt, and gravity may eventually collapse the universe in a Big Crunch.
- Shajib and Frieman’s research suggests a slower evolution of dark energy, pointing instead to a “Big Freeze,” in which galaxies drift apart, stars burn out, and the universe gradually cools into darkness.
Shajib explained that their model draws on a hypothetical ultra-light particle called the axion. “Our analysis shows that models where dark energy changes slowly over billions of years fit the data better than models where it is constant,” he said. “The density of dark energy appears to have decreased by about 10% in recent cosmic history.”
The team analyzed data from the Dark Energy Survey (DES), the Dark Energy Spectroscopic Instrument (DESI), the Sloan Digital Sky Survey (SDSS), and other major surveys. Their results rule out the standard constant dark energy model with 99.6% confidence. “This research represents the combined knowledge of the cosmology community,” Shajib said. “We may be getting closer to answering one of cosmology’s most fundamental questions.”
Dr Khan Muhammad Bin Asad, assistant professor of Physical Sciences and founding director of CASSA, highlighted the significance for Bangladesh: “CASSA is still in its early days. This also marks the beginning of astronomy and astrophysics research in Bangladesh. We are building a network that connects local research efforts with global expertise.”
Founded in 2024, CASSA is Bangladesh’s first dedicated research centre for astronomy and astrophysics. It promotes frontier research, scientific education, and public outreach, and is currently developing the country’s first radio telescope.
In December 2024, Dr Lamiya Mowla, assistant professor at Wellesley College and associate member of CASSA, made another breakthrough by uncovering new insights into early galaxy formation using NASA’s James Webb Space Telescope, published in Nature.
For more details, see Shajib’s interview on the University of Chicago website: link.