Starshade to aid exoplanet search

Light suppression is the latest concept in the search for extrasolar planets.
By | Published: July 10, 2006
July 10, 2006
Extrasolar planets are often hard to find because they get lost within the light their host stars emit. A huge, daisy-shape space shield could block out much of that light for an orbiting telescope and allow astronomers to get a better view of any earthlike planets that might lie near a targeted star, concludes a University of Colorado at Boulder (UC-Boulder) study. The findings appear in the July 6 issue of Nature.

Scientists would simultaneously launch the starshade, or New Worlds Observer, and a telescope into orbit about 1 million miles (1.6 million kilometers) from Earth — beyond the Moon’s orbit, about 238,600 miles (384,000 km) away from Earth, but well inside Mars’ orbit some 48.7 million miles (78.3 km) distant. The telescope would trail 15,000 miles (24,000 km) behind the 150-foot-wide (15 meters) starshade. Once the pair reaches orbit, scientists would remotely unfurl the starshade like flower petals and nudge it into a nearby star’s line of sight with thrusters.

unfurled starshade
The unfurled starshade would allow a telescope trailing behind the shield to capture light from a distant extrasolar planet without being swamped by starlight.
“We would use the starshade as a giant hand to suppress the light emanating from a central star by a factor of about 10 billion,” says Webster Cash, UC-Boulder professor and designer of the New Worlds Observer. The telescope would then search for suspected planets using light passing by the starshade’s edge.

The starshade’s advantage over current extrasolar planet search techniques is that it will allow astronomers to search much farther away. “We will be able to study earthlike planets tens of trillions of miles away and chemically analyze their atmospheres for signs of life,” says Cash. His innovative concept could detect surface features like water, oxygen, and methane on Moon-size planets. Most of the 194 extrasolar planets discovered so far are Jupiter-size.

Cash also envisions a group of orbiting starshades shielding a ring of Moon-based telescopes to search for new worlds.