In the mid-2020s, NASA will launch the Nancy Grace Roman Space Telescope. It will provide a panoramic field of view at least a hundred times larger than Hubble’s, at a similar resolution. It will survey the sky up to thousands of times faster than can be done with Hubble. This wide-field, high-resolution, and efficient survey approach promises new understandings of how galaxies form and evolve over cosmic time. While wide-field imaging will be necessary for galaxy evolution studies, Roman’s spectroscopic capabilities are just as important.
A spectrograph divides light from an object into a spectrum, which is a rainbow of colors. Astronomers can glean many characteristics about an object’s distance or composition from this spectrum of colors that would otherwise be unavailable. With Roman imaging and its capacity to offer a spectrum of everything within the field of view, astronomers will be able to understand more about the universe and galaxy evolution than they could with imaging or spectroscopy alone.
Astronomers can learn about the history of star creation by studying the spectrum of a galaxy in depth. They may use Roman to estimate how quickly galaxies produce stars and discover the most prolific galaxies that produce stars at a rapid rate. More importantly, they can find out not only what’s happening in a galaxy at the moment they observe it but what its history has been.