The Nancy Grace Roman Space Telescope Will Answer Fundamental Questions About the Universe

Roman was there at the dawn of space astronomy. As NASA's first Chief of Astronomy (and first female executive) in the 1960s and 1970s, she set up NASA's space astronomy program from scratch. She brought together astronomers and engineers from across the country to establish a unified list of scientific specifications for what would become the Large Space Telescope (later renamed Hubble).

Roman was dubbed "The Mother of Hubble" for her efforts. Her leadership has led to about 20 space-based telescopes, including the James Webb Space Telescope (JWST), which has already altered our perception of the early universe, and TESS (Transiting Exoplanet Survey Satellite), which has discovered dozens of planets orbiting other stars.

The latest addition to the array of space-based observatories is the Nancy Grace Roman Space Telescope, launched this past Sunday, August 30. It will take a position about 930,000 miles directly behind the Earth at an astronomical point known as the second Sun-Earth Lagrange Point (L2). It lies on a straight line extending from the Sun through the Earth out into space. 

The Lagrange Points allow space telescopes, such as the James Webb Space Telescope, Euclid, and the Nancy Grace Roman Space Telescope, to keep the Sun, Earth, and Moon continuously behind their protective sunshields while looking out into the cold, dark universe.   

The Nancy Grace Roman Space Telescope has a field of view at least 100 times larger than Hubble's, potentially measuring light from a billion galaxies in its lifetime.

“Roman will be a discovery machine that will bring us closer than ever before to answering humanity’s most profound questions about our cosmic history,” said Nicky Fox, associate administrator for the Science Mission Directorate at NASA Headquarters in Washington. “With its large field of view and fast survey speeds, Roman will usher us into a new era of discovery and make the invisible visible, setting the foundation for humanity’s search for life beyond our solar system.”

The first item on Roman's agenda is to make the first intensive search for dark matter and dark energy. These mysteries are among the most perplexing in science today. We know dark matter and dark energy exist because when we measure how fast stars orbit the center of galaxies, astronomers have found that stars at the outer edges move just as fast as those near the center. 

Based on visible mass, the outer stars should orbit much slower or fly off into space. An invisible "halo" of dark matter provides the extra gravity needed to hold them in orbit. Roman will map and study dark matter primarily through gravitational lensing — measuring how the gravity of invisible mass warps and distorts light from distant background objects as it travels through space. It's a tried-and-true method of measuring the curvature of space, allowing astronomers to pinpoint pockets of dark matter. Applying this method across vast stretches of the sky (such as with the Roman Space Telescope) allows cosmologists to track how dark matter has clumped and how dark energy has accelerated the universe's expansion over billions of years.

In addition to trying to find dark matter and dark energy, Roman will seek out new worlds among the stars.

NASA:

Roman will monitor stars scattered throughout a deep slice of the galaxy to watch for any that change in brightness. Some stars periodically dim as orbiting planets cross in front of, or transit, them. Others temporarily appear to brighten as the gravity of an intervening star and orbiting planets magnify a farther star’s light, thanks to a phenomenon called microlensing.

These two methods tend to reveal very different types of planets. The transit method, which Roman will use to reveal around 100,000 worlds, is best at finding gigantic, scorching worlds since they block the most starlight and transit more frequently.

Microlensing, which Roman will use to find more than 1,000 worlds, is better suited to finding planets with larger orbits, like those in our solar system, whose gravity can be more easily separated from the gravity of their host stars. Microlensing can find planets as small as Earth and Mars and can find them within their star’s habitable zone and even farther out. Such planets are almost undetectable by other methods and are virtually unknown outside of our own solar system. Pairing the two techniques will help astronomers explore planet formation throughout the galaxy, including Earth’s birthplace and beyond.

At $3.2 billion to build and another billion dollars in launch costs, ground communications, data processing, and primary mission operations for five years, it's not a cheap investment, but when you consider that the Hubble Space Telescope has accumulated 150 to 200 terabytes of science data over its lifetime, the textual raw equivalent of Hubble's data footprint would fill anywhere from 1,500 to 4,000 typical local libraries packed end-to-end with books.

I think it's worth it.