A new set of cosmic eyes is about to open over Florida. NASA's Nancy Grace Roman Space Telescope is preparing to launch from Kennedy Space Center in late August, and this one comes with a remarkable backstory: it will lift off eight months ahead of schedule and under budget, something almost unheard of for a flagship NASA mission.
The telescope is named for Nancy Grace Roman, who died in 2018 at age 93. Roman was NASA's first chief of astronomy and its first female executive. She helped shape the agency's space-based astronomy program and made important contributions to our understanding of stars. Now her namesake will peer deeper into the cosmos than ever before.
Roman began its journey to space in an unexpected way. It started as a spare spy satellite, donated to NASA by a U.S. intelligence agency. NASA then added two main instruments: a Wide Field Instrument and a coronagraph.
The Wide Field Instrument detects infrared light, which has wavelengths slightly longer than visible light. This allows it to see through cosmic dust and look much farther into the universe. Its field of view is about 100 times that of the Hubble Space Telescope's infrared camera, yet with similar sharpness. In fact, Roman can survey the cosmos about 1,000 times faster than Hubble. Observations that would take Hubble centuries could be completed in a fraction of the time.
The coronagraph blocks the overwhelming glare of nearby stars, much like holding a hand in front of the sun to see something faint beside it. This will help astronomers test methods for directly imaging planets and disks of dust and gas around other stars.
Over its mission, Roman is expected to detect billions of galaxies and tens of billions of stars. But its real power lies in what it might reveal about the universe's biggest mysteries.
Scientists believe ordinary matter, the stuff that makes up stars, planets, and people, makes up only a small fraction of everything in existence. About 25% is dark matter, which doesn't reflect or absorb light but helps hold galaxies together through its gravity. The remaining 70% is dark energy, a mysterious force causing the universe's expansion to accelerate.
For decades, astronomers assumed dark energy is constant everywhere. But recent results suggest it might be changing over time. Roman will test these competing ideas. If dark energy stays constant, the universe keeps expanding forever. If it changes, scientists may need entirely new theories.
Roman could also help answer why we happen to live during a moment when matter and dark energy are roughly balanced in the cosmos. This balance appears to be a cosmic intermission, brief in the universe's lifespan but lasting billions of years. It might be pure coincidence, or it might be a clue that something is missing from our understanding of the universe.
Either way, in a few months, humanity will have a powerful new tool to find out.