Sometimes just seeing stars is tough enough to demand interferometry, Hrynevych added.

"Astronomers are unable to resolve most stars for a variety of reasons," Hrynevych explains. When it comes to conventional astronomy, "Fast-spinning stars and very hot stars could be bad candidates. Another example is Cepheid stars – they pulsate fairly regularly and with an interferometer, one can detect the movement the star has gone through during its orbit." Rather than appearing within the limits of buildable dish telescopes as a blurred image like the whirling Tasmanian Devil cartoon character, "astronomers can convert this angular momentum or star position with photometrics to precisely determine the distance to the star. Knowing that velocity is equal to the wavelength of light divided by its period sharpens calculations. That star can then become a deep space mile marker to more efficiently calibrate distances." With mile markers, like on old Roman roads, astronomers could get a better fix on the elusive Hubble Constant, the red shift of light in deep space caused by Universal expansion.

The good news for any budding astronomer who wants to see "starspots" is that even ground based interferometers (which are being built in Europe, Hawaii, Chile, Arizona, and elsewhere) can see such features in 100-times greater detail than even the Hubble Space Telescope. Remember, Hubble excels at making use of every photon of light pouring into its mirror to catch faint and distant objects, but interferometers don't derive their power from light gathering. They provide sharp images from crashing light waves into each other from different receiving locations.

Still, Hrynevych concedes he harbors deep-dish dreams. "The ideal will always be a filled aperture, but technology and economics rarely allow astronomers to build larger diameter optical telescopes than what are available today," commented Hrynevych.

Even the planned California Extremely Large Telescope and the Overwhelmingly Large Telescope in Germany, each costing hundreds of millions of dollars and perhaps two decades away from construction, wouldn't reach nearly the size needed to pick out star spots. And those huge machines would be based on the ground, below rippling waves of atmosphere. Adaptive optics, a process that can compensate for such disturbances by bending mirrors in countless ways at once, can achieve amazing results but there's no replacement for being in space.

"The best adaptive optics looks like when the Hubble was broken," said Ray Villard, a spokesman for the Space Telescope Science Institute and a professed "chauvinist for filled apertures." His analogy is apt: "It's like having a device that filters out the pops and scratches on a vinyl LP record. No thank you, I'll have my CD."

Hrynevych agrees. "For spectroscopy this is not a big deal, but for imaging it is." 

Even the revered Hubble has a reflector only 2.8 meters across – its power comes from using photons more efficiently in the vacuum of space. But missions to spot planets like Earth in other systems, "calls for Battlestar Galactica space telescopes," Villard remarked.

But launching a huge dish isn't current an option either – whatever goes up must fit in a cargo bay or be assembled in orbit. Radical ideas for folded, segmented, or gossamer mirrors that can be unfurled in space have been proposed, and some show great promise. But it's into this void that interferometers have most boldly stepped. StarLight, the first space-borne stellar interferometer, will combine the light of two small telescopes to create a 125-meter "virtual" telescope. The distance between the telescopes will have to be precisely controlled, straying by no more than 10 centimeters. The bar for SIM is even higher -- nanometer-level control and stabilization and even more precisely honed coordination of optical elements.

"It all goes back to why someone would build an interferometer. The goal of larger telescopes is to increase resolution and sensitivity. Current technological limitations prevent us from building a 100-meter telescope. However, we can achieve the resolution power of an 85-meter telescope at Keck by using interferometry," Hrynevych said. Keck is already linking up its two 10-meter telescopes to produce the largest optical interferometer in history, and using a Hawaiian metaphor, those central dishes will be augmented by smaller "outrigger" units. Right now Jupiter-sized worlds are typically spotted through spectral anomalies or wobbles in their host stars rotations. The Keck's goal is to see those gas giants directly. That's ambitious, but blunt compared with even initial efforts like StarLight and SIM. It's clear the way is space for future interferometers.