June 10, 2013
New Technique For Hunting Exoplanets In The Works
Lee Rannals for redOrbit.com - Your Universe Online
Sponsored by the International Astronomical Union (AIU), a team of astronomers is working on a technique capable of detecting faint dust clouds around other stars where Earth-like planets could be hiding. This new technology could dramatically improve the odds of discovering planets with conditions suitable for life.
"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," explained Denis DefrÃ¨re, a postdoctoral fellow in the University of Arizona's (UA) department of astronomy and instrument scientist of the Large Binocular Telescope Interferometer (LBTI). "We want to be able to detect fainter dust clouds, which would dramatically increase our chances of finding more of these planets."
Exoplanets orbiting nearby stars are typically concealed by vast clouds of dust enveloping the star and its system of planets.
"If you see a dust cloud around a star, that's an indication of rocky debris, and it increases the likelihood of there being something Earth-like around that star," said Phil Hinz, an associate professor of astronomy at the UA's Steward Observatory. "From previous observations, we know that these planets are fairly common. We can expect that if a space telescope dedicated to that mission were to look around a certain area of sky, we'd expect to find quite a few."
The astronomers are working on developing an instrument that will allow scientists to detect fainter clouds that are only about 10 times brighter than the one in our own solar system.
"It's like being here in Victoria and trying to image a firefly circling a lighthouse in San Francisco that is shrouded in fog," DefrÃ¨re said about the technological challenge. "That level of sensitivity is the minimum we need for future space telescope missions that are to characterize Earth-like planets that can sustain liquid water on the surface. Our goal is to eliminate the dust clouds that are too bright from the catalog of candidates because they are not promising targets to detect planets suitable for life."
Hinz said with a bright dust cloud its light becomes comparable to that of its star, making it easier to detect. Fainter clouds can be about 10,000 times less bright than their star, so it becomes difficult or impossible for observers to make out their faint glow in the star's overpowering glare.
"To do that, one would need a space telescope specifically designed for this type of imaging," he said. "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."
The astronomers plan on using a technique known as nulling interferometry and the unique configuration of the LBTI.
"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," Hinz explained. "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."
NASA's exoplanet hunting instrument Kepler has been a choice tool for astronomers hunting for these other worlds. However, this spacecraft's mission came to a close back in May unexpectedly when Kepler went into a thruster-controlled safe mode. This instrument has helped scientists identify more than 2,300 planet candidates and confirm more than 100 planets so far.