An international team of exoplanet hunters, including astronomers at the University of Arizona, is developing a new technology that would dramatically improve the odds of discovering planets with conditions suitable for life -- such as having liquid water on their surface.
Terrestrial planets orbiting nearby stars often are concealed by vast clouds of dust enveloping the star and its system of planets. Our solar system, too, has a dust cloud, which consists mostly of debris left behind by clashing asteroids and exhaust spewing out of comets when they pass by the Sun.
“Current technology allows us to detect only the brightest clouds, those that are a few thousand times brighter than the one in our solar system,” said Denis Defrere, a postdoctoral fellow in the UA’s department of astronomy and instrument scientist of the Large Binocular Telescope Interferometer (LBTI).
He explained that while the brighter clouds are easier to see, their intense glare makes detecting putative Earth-like planets difficult, if not impossible.
Phil Hinz, an associate professor of astronomy at the UA’s Steward Observatory, and Defrere are working on an instrument that will allow astronomers to detect fainter clouds that are only about 10 times -- instead of several thousand times -- brighter than the one in our solar system.
Funded by NASA, the team is in the middle of carrying out tests to demonstrate the feasibility of these observations using both apertures of the Large Binocular Telescope, or LBT, in Arizona. The project aims at determining how difficult it would be to achieve the desired results before committing to a billion-dollar space telescope mission.
“Our goal is to do a feasibility study of whether it would be possible to distinguish the light emission of the planet from the background emission of the dust cloud through direct observation,” Hinz said.
The researchers take advantage of a technique known as nulling interferometry and the unique configuration of the LBT, which resembles a giant pair of binoculars.
“We combine the light from two apertures, cancel out the light from the central star, and with that it becomes easier to see the light from the dust cloud. To achieve this, we have to cause the two light paths to interfere with each other, which requires lining them up with very high precision. We’ll always have some starlight left because of imperfections in the system, but our goal is to cancel it out to a level of 10,000 to get down to where we can at least detect the faint glow of the dust cloud,” Hinz explained.
The work used the same technique with the two large telescopes of the Keck Observatory in Hawaii in order to detect the dust cloud around the star Fomalhaut located 25 light-years from our Sun.
The team presented its results at a scientific conference sponsored by the International Astronomical Union in Victoria, British Columbia.