Noelia Noël
NASA is preparing to launch a flagship space observatory that could help resolve some of the deepest mysteries in modern astronomy. The Nancy Grace Roman space telescope will study how the universe began, what it is made of, and how it has evolved over time.
Named after NASA’s first chief of astronomy and its first female executive, the mission honours Nancy Grace Roman, who passed away in 2018 at the age of 93. She made fundamental contributions to stellar physics and played a pivotal role in shaping space-based astronomy programmes.
The telescope is undergoing final preparations ahead of its launch from Florida’s Kennedy Space Center in late August. Remarkably, it is running eight months ahead of schedule and under budget a rare achievement for a NASA flagship project.
While the James Webb space telescope focuses on individual cosmic objects in extraordinary detail, Roman is engineered to survey the sky at scale. Originally starting life as a spare spy satellite donated by a US intelligence agency, NASA fitted the observatory with two main instruments: the Wide Field Instrument and the Coronagraph.
The Wide Field Instrument detects infrared light, enabling it to pierce through cosmic dust and view deeper space. Its field of view is about 100 times larger than the Hubble Space Telescope’s infrared camera while maintaining similar sharpness. Consequently, Roman can survey the cosmos nearly 1,000 times faster than Hubble, completing observations in a fraction of the time that would otherwise take centuries.
Meanwhile, the Coronagraph suppresses the blinding glare of nearby stars, acting much like a hand blocking the Sun to reveal fainter surroundings. This will allow astronomers to test novel techniques for directly imaging exoplanets as well as circumstellar discs of dust and gas.
Over its operational lifetime, Roman is expected to detect billions of galaxies and tens of billions of stars. This combination of vast coverage and sharp precision will allow astronomers to uncover broad cosmic patterns while measuring subtle gravitational effects.
Modern cosmology relies on a model where ordinary matter which forms stars, planets, and humans accounts for only a tiny fraction of the universe. The remaining 95% consists of two invisible, mysterious components: dark matter and dark energy.
Dark matter makes up roughly 25% of the universe. It neither reflects nor absorbs light, yet its gravitational force holds galaxies together. Roman will trace how dark matter shaped galaxy formation across cosmic history.
Dark energy accounts for about 70% of the cosmos and drives the accelerating expansion of the universe. While long assumed to be constant, recent findings suggest dark energy might evolve over time. Roman will test these competing theories. If dark energy changes, it could reveal completely new physics beyond current scientific understanding.
The telescope will also address why we exist in a rare cosmic intermission where the densities of matter and dark energy are roughly comparable. Beyond cosmology, Roman will conduct the largest search yet for exoplanets, using gravitational microlensing to discover thousands of new worlds.