Now that they knew where the Ythri star was, she found the earlier Ythri signals from records from the Long Now Cave. These were spectral data of irregular “pulsars” seen in the 2100s and not again. Brief, compressed, they repeated only a few times. Astronomers had assumed these were some kind of errant pulsars. Wrong. She found they were in fact SETI signals from the Ythri, hundreds of light-years away. These flashes around 10 GHz were attempts to reach Earth, assuming a tech civilization might be there, based on the Ythri detection of the ozone line in our atmosphere. These were not understood during the decades following the Age of Appetite, when no one had puzzled out the economics of SETI contact, and so did not realize that short bursts were far more efficient as attention-getting signals. The smart strategy was to send lighthouse pulses, catch the attention of emerging societies, and direct them to a much lower power signal that carried detailed messages. Nobody in the slowly collapsing decades of the late 2000s and all of the 2100s caught on. Nor could they remotely afford to reply. The whole of humanity was putting out fires, often literally. Still, in the middle decades of the 2000s Earth had sent “slow boat” solar sails out into the Oort cloud, bound for Centauri and beyond. Making close solar passes in “sundiver” mode got them up to 500 or 600 kilometers per second, a thousandth of the speed of light. In thousands of years they could arrive at stars, after dutifully passing data on interstellar space back to Earth. Most of these were still on the way, forlorn robot voyagers long outdated in their very mission.

But the Furians, as Fraq termed them, had thought on even longer perspectives before humans evolved. Rachel researched Fraq’s tale, and found fragments that implied the Ark story made sense.

The deeply ancient Furian civilization had reached its end as their sun left the main sequence and became a red giant, its luminosity rising by a factor of a thousand. The swelling ruddy sphere doomed their world, but also brimmed with photons, a rich launcher for Furian solar sails. That dropped the time for an interstellar transit down to centuries. Sailcraft wouldn’t last forever in transit, when they might smack into a random rock. Best to keep the sailing time low.

But how could the craft slow down when they arrived? Their light sails would be nearly useless for getting captured into the gravity well of a main-sequence star, with its puny sunlight. A magnetic sail, braking on the solar wind, could help, but not nearly enough. Without something more, the Arks the dying Furian world sent out would simply blow by their target stars. The Furians, Fraq said, had identified stars with circling worlds known to have working biospheres, but that gave forth no SETI signals, no leakage of artificial emissions, nothing. Someday they might harbor intelligence, and the Arks could carry the life lore of the long-dead Furians down to the next generation of life in the galaxy. A cultural and biological legacy. Better than a funeral pyre, or a repeating microwave robo-message touting Furian art and culture and religion to the cold stars.