Starshades could enable direct imaging of exoplanets

By creating artificial eclipse, starshade would enable accompanying telescope to observe a star's orbiting planets.
By Kathy Fey | Aug 26, 2017
As a means of enabling direct imaging of exoplanets, scientists are exploring the use of starshades, spacecraft that would block the light of a star, creating an artificial eclipse and allowing a second spacecraft equipped with a telescope to directly observe orbiting planets.

A majority of the 3,500 exoplanets discovered have only been indirectly observed. Potential Earth-like planets in stars' habitable zones cannot be directly detected because of the glare of their host stars, which can be up to 10 billion times brighter than the planets themselves.

In order to successfully image an Earth-sized planet, a starshade would have to have a diameter of tens of meters placed several Earth diameters apart from the telescope. Both would have to be deployed beyond Earth's orbit.

"With indirect measurements, you can detect objects near a star and figure out their orbit period and distance from the star," explained Simone D'Amico of Stanford University, who serves as director of the university's Space Rendezvous Laboratory.

"This is all important, but with direct observation, you could characterize the chemical composition of the planet and potentially observe signs of biological activity--life."

To illustrate the benefit of this technology, D'Amico, and colleague Bruce MacIntosh has created a smaller version of these objects, hoping to showcase them to scientists in a low-cost flight demonstration.

They labeled the system, which includes a three-meter-diameter starshade and a 10-cm-diameter telescope, both of which sit on separate 10-kg tiny satellites, as mDOT, which stands for miniaturized distributed occulter/telescope.

The starshade will be folded at launch, then open up while in Earth orbit. Both it and the telescope will be placed in high-Earth orbit separated by less than 1,000 km.

Although the test starshade will not be powerful enough to directly image Earth-like exoplanets, it may be capable of observing planets the size of Jupiter.

Still in development, the test system would cost several million dollars, in contrast to several billion for the actual spacecraft.

MDOt is one of the several projects that involve multiple spacecraft flying in formation now under development at the Space Rendezvous Laboratory.

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