DATA BANK
By the second half of the twenty-first century astronomers had detected several thousand planets orbiting other stars. Most of these exoplanets were gas giants, bloated spheres of hydrogen and helium, totally unlike Earth. But a few percent of them were small, rocky worlds, more like our own.
One in particular raised hopes of being really Earthlike: Sirius C. It was almost the same size as Earth, and although its parent star was a fiercely blazing blue-white giant, much larger and hotter than the Sun, the planet’s orbit lay at the “Goldilocks” distance from Sirius where its surface temperature was not too hot, and not too cold for liquid water to exist.
On Earth, liquid water means life. Beneath the frozen iron sands of Mars, liquid water melting from the permafrost hosts an underground biosphere of microbial life-forms. In the ice-covered seas of Jupiter’s major moons, living organisms abound. In the planet-girdling ocean beneath the eternal clouds of giant Jupiter itself, life teems and flourishes.
Sirius C was a challenge to the astrobiologists. It couldn’t possibly bear life, Goldilocks notwithstanding, not sandwiched between brilliant Sirius A and its dwarf star companion, Sirius B. The dwarf had erupted in a series of nova explosions eons ago. The death throes of Sirius B must have sterilized any planets in the vicinity. But there it was, a rocky, Earth-sized planet, the only planet in the Sirius system, orbiting Sirius A in a nearly perfect circle.
Might there be a chance that the planet did harbor some kind of life-forms? The astrobiologists worked overtime concocting theories to support the hope that the Earth-sized planet might indeed host an Earth-type biosphere. The popular media had no such problem. They quickly dubbed Sirius C “New Earth.”
Orbiting in a zone where water could be liquid did not necessarily mean that Sirius C actually had liquid water on its surface. Astronomers all across Earth—and on the Moon—strove to discover water, oxygen, other clues to the presence of life on the exoplanet.
Detecting the planet was not the same as imaging it. Sirius C was discovered by the minute gravitational tugs it exerted on its parent star. Then telescopes in orbit measured the tiny dip in light output from Sirius A when the planet transited across its star’s shining face. From these data the eager astronomers of Earth deduced the planet’s size and surface temperature.
Now the task was to get visual images of the planet, to photograph its surface and measure the constituents of its atmosphere—if it had an atmosphere. No telescope on Earth could produce such imagery at a distance of nearly eighty-four trillion kilometers.
Not even the telescopes in space could reveal much more than a blurry speck of a disc. But calculations showed that a set of very large telescopes, working together as an optical interferometer, might be able to resolve surface features on Sirius C. The telescopes would have to be in space, clear of the Earth’s murky, turbulent atmosphere.
Owing to the driving ambition of Anita Halleck, the International Astronautical Authority decided to build such an interferometer in solar orbit. Its segmented mirrors would be placed at opposite locations along the Earth’s orbit, producing an instrument with a baseline of two astronomical units: nearly two hundred million kilometers.
The lunar nation of Selene was already constructing a radio telescope facility on the far side of the Moon, where it would be insulated from all the radio chatter of Earth by more than three thousand kilometers of rock. Farside, the side of the Moon that is permanently pointed away from Earth, was the quietest place in the solar system for sensitive radio searches for intelligent life.
The radio telescope, dubbed Cyclops, was to consist of a thousand dish-shaped antennas, each one a hundred meters across, covering a total area ten kilometers wide.
When the IAA announced its plans for the space-based optical interferometer, one of Selene University’s distinguished astronomers, Professor Jason Uhlrich, proposed building a more modest optical instrument on the Moon’s far side. After all, the surface of the airless Moon was effectively in space. The vacuum at the lunar surface was actually a thousand times thinner than the vacuum in Earth orbit. Lunar materials could be used to build the telescopes, and the Moon offered a firm platform for them.
So the Farside Observatory became the site for an optical interferometer consisting of three interlinked telescopes, each with a main mirror of one hundred meters, slightly larger than an American football field, more than twice the size of any telescope mirror built on Earth. They were to be erected in three giant craters: the longest distance between them would be about eighteen hundred kilometers.
And in the midst of the optical instruments, the Cyclops radio telescope was being erected. Professor Uhlrich was named to head Farside Observatory. He enthusiastically proclaimed that the observatory would be the finest and most important astronomical facility in the solar system.
Yet, even in the gentle gravity of the Moon, building such large and complex structures was a challenge to the skill and knowledge of the men and women who came to Farside.
More than anything else, it was a test of their perseverance and their heart, a challenge that brought out the best in some of them.
In some of them it brought out the worst.