The new NASA space telescope will hunt down exoplanets
Roman will use his Coronagraph Instrument, a system of masks, prisms, detectors and even self-flexing mirrors built to block the glare of distant stars and reveal planets orbiting them, to demonstrate that direct imaging technologies can work even better in space than on earth.
"We will be able to photograph worlds in visible light," said Rob Zellem, an astronomer at NASA's Jet Propulsion Laboratory (JPL) in Southern California who is co-leading the observation calibration plan for the instrument. JPL is building the Roman coronary instrument. "Doing this from space will help us see planets smaller, older and colder than direct imaging usually reveals."
Exoplanets, planets beyond our solar system, are so distant and faint compared to their host stars which are practically invisible, even to powerful telescopes. That is why nearly all of the worlds discovered so far have been found indirectly through the effects they have on their host stars. However, recent technological advances allow astronomers to actually take images of the light reflected from the planets themselves.
If the Roman coronary instrument successfully completes its technology demonstration phase, its polarimetry mode will allow astronomers to view the discs around stars in polarized light. Astronomers will use polarized images to study the dust grains that make up the disks around stars, including their sizes, shapes and possibly mineral properties. Roman may also be able to reveal structures in the discs, such as gaps created by invisible planets. These measurements will complement existing data by probing fainter dust disks, which orbit closer to their host stars, hitherto impossible to see with other telescopes.
Current direct imaging efforts have been limited to huge, bright planets . These worlds are typically super-Jupiter less than 100 million years old, so young that they glow brightly thanks to the residual heat of their formation, which makes them detectable in infrared light. They also tend to be very far from their host stars because it is easier to block the star's light and see planets in more distant orbits. Coronagraph Roman could complement infrared observations from other telescopes by photographing young super-Jupiter in visible light for the first time, according to a study by a team of scientists.
“To spot Earth-like planets, we will need 10,000 times better performance than instruments today, ”said Vanessa Bailey, JPL astronomer and instrument technologist for the Coronagraph Roman. "The Coronagraph Instrument will perform several hundred times better than current instruments, so we will be able to see Jupiter-like planets that are more than 100 million times fainter than their host stars."
A team of scientists recently simulated a promising target called Upsilon Andromedae d. "This gas giant exoplanet is slightly larger than Jupiter, orbits within the habitable zone of a Sun-like star and is relatively close to Earth, just 44 light-years away," said Prabal Saxena, research assistant at the University of Maryland, College Park and NASA's Goddard Space Flight Center in Greenbelt, Maryland, and lead author of a paper. “What's really exciting is that Roman might be able to help us explore mists and clouds in Upsilon's atmosphere Andromedae de might even be able to act as a planetary thermometer by placing constraints on the planet's core temperature!”
The Coronagraph Roman will also be equipped with deformable mirrors, which help to counteract the small imperfections that reduce the quality of the image. These special mirrors will measure and subtract starlight in real time, and technicians on the ground will also be able to send commands to the spacecraft to adjust them. This will help counteract effects such as temperature changes, which can slightly alter the shape of the optics.
Using this technology, Roman will observe planets so faint that special detectors will count single photons of light as they arrive, just a few seconds or even minutes away. No other observatory has done this type of visible light imaging before, providing a vital step towards the discovery of habitable planets.
