NASA's New Telescope Will Map the Universe's Empty Spaces
NASA's Nancy Grace Roman Space Telescope will help scientists map the vast empty regions of space when it launches. These regions, called cosmic voids, are the gaps between galaxies. They take up about 95% of the space in the universe.
The Roman telescope will be able to spot tens of thousands of these voids, even small ones that stretch across 20 million light-years. Its wide view and sensitive instruments will pick up distant, faint galaxies that earlier telescopes missed. Those galaxies mark where the empty spaces begin and end.
What are Cosmic Voids?
Think of the universe like Swiss cheese. The holes are cosmic voids — mostly empty space. The solid parts are where galaxies cluster together along long threads called filaments. These voids formed early in cosmic history, when small differences in density grew over billions of years.
Cosmic voids matter to scientists because they can help explain two big mysteries: what is dark matter, and what is dark energy. Dark matter and dark energy make up most of the universe, but we cannot see them directly. Voids offer a clean way to study how gravity works on the largest scales.
What We Know Today
Earlier telescopes have already mapped some cosmic voids. The Sloan Digital Sky Survey created a 3D map of the sky stretching 2 billion light-years deep. It showed the web-like structure of the universe — thick strands of galaxies separated by enormous empty spaces. The European Space Agency's Planck satellite added information about how dark matter is spread throughout space.
More recent data from the Euclid mission shows galaxies sitting on the edges of huge empty bubbles, confirming that voids are real and widespread.
Why Roman is Different
The Roman telescope will see farther and clearer than these earlier surveys. Its instruments are designed to detect very faint, distant galaxies that current telescopes cannot easily spot. That means it can find and measure smaller voids — down to 20 million light-years across — than earlier surveys, which typically could only detect structures hundreds of millions of light-years across.
NASA's Goddard Space Flight Center, the Jet Propulsion Laboratory, and other institutions are working together on the Roman mission. The Roman telescope is named after Nancy Grace Roman, an astronomer who pioneered space telescopes.
What Scientists Will Learn
A better void map will help scientists test theories about how the universe expands and how gravity works on cosmic scales. Some researchers have proposed that our galaxy might sit near the center of a large void — a hypothesis that could explain certain oddities in observations of the cosmic microwave background, the oldest light in the universe.
Computer simulations can now reproduce the distribution of galaxies and voids that we observe in our universe. This gives scientists confidence that they understand, in broad strokes, how structure forms and evolves.
The broader context here is that Roman's void measurements will work alongside other new surveys, including the Dark Energy Spectroscopic Instrument, to refine our understanding of cosmic expansion. For decades, cosmology has wrestled with the fact that 95% of the universe's energy is in forms we do not fully understand. Mapping the 95% of space that is mostly empty offers a new angle on that puzzle.
When the Roman telescope launches, its catalog of voids will represent a significant step forward for a field that is still working to answer one of its oldest questions: what is the universe actually made of, and how did it take the shape we see today.
