NASA’s Nancy Grace Roman Space Telescope is poised to become a cornerstone of astronomical research, offering unprecedented insights into the history of our galaxy and the nature of dark matter.
Scheduled for launch in 2027, the Roman Telescope will investigate the Milky Way and other nearby galaxies, providing astronomers with the tools needed to explore the origins and evolution of these cosmic structures.
The telescope’s advanced capabilities are expected to reveal new details about galactic fossils—ancient stellar remnants that serve as records of a galaxy’s formation—and to shed light on the mysterious dark matter that makes up most of the universe’s mass.
Investigating Galactic Fossils with Roman
One of the primary objectives of the Roman Space Telescope is to study galactic fossils, which are groups of ancient stars that hold vital clues about the formation and evolutionary history of galaxies. These stellar remnants can include large-scale structures like tidal tails, stellar streams, and halo stars that extend far beyond the visible portions of galaxies. By capturing high-resolution images of these features, the Roman Telescope will allow scientists to reconstruct the events that shaped galaxies over billions of years.
Robyn Sanderson, the deputy principal investigator of the Roman Infrared Nearby Galaxies Survey (RINGS) at the University of Pennsylvania, likened the process of studying these galactic fossils to an archaeological excavation. "It’s like going through an excavation and trying to sort out bones and put them back together," Sanderson said. The Roman Telescope’s ability to observe vast areas of the sky with high angular resolution will enable researchers to piece together these cosmic clues, providing a clearer picture of how galaxies like the Milky Way have evolved.
The challenge of understanding our own galaxy’s history is compounded by our position within it. Professor Raja GuhaThakurta from UC Santa Cruz highlighted this limitation, stating, "We simply don’t have a selfie stick long enough to take those kinds of photos." The Roman Space Telescope, however, will offer a unique vantage point by allowing scientists to study other galaxies that are similar to the Milky Way. By comparing these external galaxies to our own, researchers can infer the processes that have shaped the Milky Way, offering a broader context for understanding our place in the cosmos.
Shedding Light on Dark Matter
In addition to exploring galactic fossils, the Roman Space Telescope will play a crucial role in investigating dark matter, a substance that makes up about 80% of the universe’s mass but remains largely undetectable by conventional observational methods. Dark matter is thought to be responsible for the gravitational forces that bind galaxies together, yet it does not emit, absorb, or reflect light, making it invisible to traditional telescopes.
The RINGS survey, a potential project for the Roman mission, will focus on studying the halos of galaxies, which are regions dominated by dark matter. These halos extend far beyond the visible boundaries of galaxies and are often 15 to 20 times larger than the galaxies themselves. By observing the distribution of stars and other matter within these halos, the Roman Telescope will provide critical data for testing dark matter theories and understanding its role in galaxy formation.
Ultra-faint dwarf galaxies are particularly valuable for studying dark matter because they contain very few stars and are almost entirely composed of dark matter. GuhaThakurta explained, "Ultra-faint dwarf galaxies are so dark matter-dominated that they have very little normal matter for star formation. Even when they do form stars, the process will blow away more of the gas needed to create the next generation of stars, so they are deeply inefficient at producing stars." These galaxies, therefore, act as nearly pure dark matter laboratories, offering a unique opportunity to study this elusive substance.
By providing high-resolution images of these faint galaxies and their surrounding halos, the Roman Telescope will enable scientists to observe the effects of dark matter on a much larger scale than currently possible. As Ben Williams, principal investigator of RINGS at the University of Washington, noted, "With Roman, all of a sudden we’ll have 100 or more of these fully resolved galaxies," significantly expanding the dataset available for dark matter research.
A New Era of Galactic Exploration
The Nancy Grace Roman Space Telescope represents a significant leap forward in our ability to explore and understand the universe. Often referred to as the "mother" of the Hubble Space Telescope due to its advanced capabilities, the Roman Telescope is expected to revolutionize our understanding of both visible and invisible components of galaxies. Its large field of view and high resolution will allow astronomers to study not only individual stars and stellar populations but also the broader structures that govern the evolution of galaxies.
By combining the Roman Telescope’s imaging data with deep, wide-field spectra from ground-based telescopes like the Keck II 10-meter telescope and the DEIMOS spectrograph, scientists will be able to apply advanced techniques, such as co-added surface brightness fluctuations (SBF) spectroscopy. This method, which GuhaThakurta helped develop, promises to enhance our understanding of the formation and evolution of galaxies, ranging from those comparable in size and luminosity to the Milky Way to much smaller or larger systems.