Scanning vast swaths of sky, NASA’s next flagship observatory, the Nancy Grace Roman Space Telescope, promises to revolutionize our understanding of dark matter and dark energy while discovering some 100,000 exoplanets.
The minimum five-year survey mission – targeting launch from Florida no earlier than Aug. 30 – also includes a technology demonstration that will attempt a first in space: direct imaging of exoplanets in visible light wavelengths.
NASA’s Nancy Grace Roman Space Telescope on Aug. 7, after engineers and technicians at Kennedy Space Center had mated the observatory to a payload adapter, before it was secured to the second stage of a SpaceX Falcon Heavy rocket.
As a principal investigator supporting Roman’s state-of-the-art coronagraph – an instrument designed to block out direct light from a star or another bright object – Cornell faculty member Dmitry Savransky has helped determine the targets that the instrument will study and when best to observe them. Capturing pictures of these previously hidden, Jupiter-like planets, he said, marks a first step toward directly imaging potentially habitable Earth-like planets.
“If we are successful, it would be incredibly compelling and exciting scientifically, because this will be a unique dataset that literally doesn’t exist,” said Savransky, associate professor of mechanical and aerospace engineering in the Cornell Duffield College of Engineering, and of astronomy in the College of Arts and Sciences. “No other space observatory has this capability.”
Savransky plans to attend the telescope’s launch from Kennedy Space Center aboard a SpaceX Falcon Heavy rocket, along with three doctoral students who have supported the work: Isabela Huckabee, Saanika Choudhary and Rifah Tasnim.
The observatory’s primary mission features the Wide Field Instrument, a 300-megapixel infrared camera with a field of view 100 times larger than the Hubble Space Telescope’s, collecting data 1,000 times faster. Surveys of nearly the entire sky are expected to massively expand the catalog of known exoplanets, which now number nearly 6,200.
The coronagraph demonstration, in contrast, aims to provide detail about a small number of individual planets or planetary disks known to exist, but that have been obscured by their host stars’ bright glare. NASA says the adaptive instrument’s system of optics, masks, self-flexing mirrors and sensors is designed to block that glare, allowing scientists to access the faint light reflected or emitted by orbiting planets.
Among the likely first targets is Epsilon Eridani b, believed to be a close analog of Jupiter and orbiting a similar distance from its star, just 10 light years away. It has been detected only indirectly, through minute shifts in the color of starlight collected by a ground-based telescope.
“It’s an incredibly difficult observation to make, right at the borderline of our technological capabilities, and so we’re going to try to do it with Roman,” Savransky said. “So many individual things have to go right for all this to work.”
Ground-based telescopes can directly image certain exoplanets: very young, hot planets, such as baby Jupiters or larger planets, seen in the infrared. The Roman coronagraph, from its position 1 million miles from Earth at the second Sun-Earth Lagrange point – the same neighborhood as NASA’s James Webb Space Telescope (JWST) – aims to reveal planets that are older, colder and in orbits closer to their stars.
Don’t expect awe-inspiring scenes like those Hubble and JWST observations have produced of galaxies and dust clouds. Portraits of Epsilon Eridani b and other targets will simply look like pixels – “literally just a dot,” Savransky said. Embedded in that dot, however, will be valuable information about the exoplanets’ atmospheres, which will be key to future assessments of habitability.
“Thinking ahead to when we try to do this for Earth-like planets, we’re particularly interested in visible wavelengths because a lot of good spectral signatures are biomarkers,” Savransky said. “We’ll need many lines of evidence before we can say a planet out there has life as we know it, but we need to start building up the toolkit that will eventually allow us to make those conclusions.”
As a technology demonstration subject to limited testing, the complex coronagraph observations carry higher risk than is typical for a flagship NASA science mission, Savransky said. But after years of planning, he hopes Roman – named for NASA’s first chief astronomer – begins revealing exoplanets by early next year, and imparting lessons that could inform the proposed Habitable Worlds Observatory.
“We’re going to try to do this for the very first time from a space observatory, and it’s going to teach us a lot about building the next generation,” Savransky said. “We will see this light that was actually bounced off of an actual planet, decades or centuries ago, and we will get to perceive it. That to me is incredibly exciting.”
