lost planet

Xiao Yu did not visit Uranus, as it was on the opposite side of the Sun at the time. However, calculations showed that after traveling an additional two billion kilometers, Xiao Yu's fleet would graze Neptune's orbit, offering a rare chance to observe the planet up close.

At this moment, Xiao Yu's fleet was traveling at 500 kilometers per second relative to the Sun.

During the long voyage, Xiao Yu arranged the fleet in a spherical formation. At the core were three county-level ships, surrounded by seventy township-level ships, and further out, a thousand village-level ships encircled the others, forming a massive sphere with a diameter of ten thousand kilometers. Xiao Yu commanded from the center, leading the fleet on its grand journey through space.

Ahead of the fleet, village-level ships, serving as sentinels, periodically fired lasers to vaporize any asteroids in their path. The fleet moved through the solar system like a crab, advancing relentlessly.

Soon, the deep blue of Neptune appeared in Xiao Yu's view. From this vantage point, he could see the planet's Great Dark Spot and observe Triton, Neptune's largest moon, up close.

Triton, once a Kuiper Belt object, had been captured by Neptune's strong gravity, resulting in its retrograde orbit. It was gradually inching closer to Neptune, and once it crossed the Roche limit, it would be torn apart by the planet's gravity, with its fragments eventually colliding with Neptune.

This event would rival the magnitude of the Jupiter-Shoemaker-Levy 9 collision, though its distance from the inner planets would prevent any significant impact on them.

Xiao Yu did not slow down his fleet. Having resolved to leave the solar system, no sight, however magnificent, could make him pause.

His encounter with Neptune was fleeting. Rather than lingering, Xiao Yu used Neptune's gravity to accelerate his fleet to 520 kilometers per second.

A month later, the fleet reached Pluto's orbit. After briefly observing the distant Pluto through a telescope from 300 million kilometers away, Xiao Yu continued toward the outer solar system.

This region was the domain of the Kuiper Belt, the birthplace of short-period comets within the solar system. Famous comets like Halley's were believed to originate from here, though Xiao Yu was not fortunate enough to encounter it. The comet's current whereabouts within the solar system remained unknown.

At a distance of six billion kilometers from the Sun, it now appeared only slightly brighter than Venus as seen from Earth. It had become a mere point of light, devoid of detail. Yet even from this great distance, the Sun still dominated everything in the Kuiper Belt, including Pluto, Eris, and Sedna, which, along with countless icy bodies, continued their orbits around the distant point of light.

The region was cold and dark. Loneliness was the eternal melody of the universe, and light was a rare and fleeting sight.

In this vast expanse, there were at least a hundred million objects, yet Xiao Yu could see none. Compared to the vastness of this space, the density of matter was astonishingly low.

Xiao Yu pressed onward. In the emptiness of space, with no reference points, there was no sense of motion. His vast fleet floated silently, without a trace of movement.

Throughout the nine-month journey, Xiao Yu kept a close watch on the strength of the solar wind. He observed it gradually weakening, indicating that the Sun's influence was waning in this distant region.

Slowly, the solar wind's speed decreased from hundreds of kilometers per second to below the speed of sound at 340 meters per second. Xiao Yu knew that he had reached the edge of the solar system.

Beyond lay the realm of the interstellar medium. The Sun, with its powerful energy, had carved out a space for itself within this medium, and Xiao Yu now stood at the boundary between the solar empire and the interstellar medium.

This was the heliopause, 18 billion kilometers from the Sun.

Under the influence of the interstellar medium, the solar wind's speed finally dropped below the speed of sound. Here, solar wind and interstellar medium engaged in a fierce battle, with countless particles colliding in an unseen frenzy, and temperatures soaring to thousands of degrees Celsius.

Indeed, it was cold and dark here. A human would instantly freeze solid, yet the temperature was thousands of degrees Celsius.

Temperature was merely a measure of the intensity of molecular motion. Here, the matter was so sparse that despite the high temperature, it had no impact on Xiao Yu. It was similar to the Earth's ionosphere, where temperatures exceeded a thousand degrees, yet artificial satellites still flew freely.

This was the final battlefield. In its struggle with the interstellar medium, the solar wind had been utterly defeated. Xiao Yu knew that once he crossed this boundary, the Sun would no longer exert any influence beyond gravity.

It took Xiao Yu two days to traverse the heliopause. Watching as the number of high-energy charged particles from the Sun slowly dwindled and then finally disappeared, and gazing at the distant point of light that had dimmed and now resembled any other star in the universe, Xiao Yu felt a profound mix of emotions.

"Mother, dearest Mother, farewell, farewell," Xiao Yu murmured, feeling an overwhelming urge to weep.

Ahead lay the interstellar medium, a realm dominated by hydrogen and helium from the Milky Way. The matter here was so thin that there was less than one atom per cubic centimeter. Such a density was akin to spreading a drop of water across five million cubic kilometers.

Awaiting Xiao Yu ahead was a journey of over six thousand years through this vast, empty space.

After crossing the heliopause, Xiao Yu remained despondent for a year. During this time, he was in a state of mental daze, leaving the fleet's daily operations to automated programs. Xiao Yu spent his days gazing through the telescope, lost in memories, staring in the direction of the Sun. Fortunately, the course had long been set, and there was no risk of asteroid collisions, so no accidents befell the fleet.

Now, Xiao Yu was 35 billion kilometers away from the Sun. It took light 32 hours to reach this distant location. Yet, even at such a vast distance, Xiao Yu made a significant discovery.

He found a planet.

Yes, a planet that had achieved hydrostatic equilibrium, with enough mass to clear its orbital path of other celestial bodies. By all definitions, it was a planet.

Its mass was 1.5 times that of Earth, and it was a rocky planet, orbiting the Sun at an incredibly slow pace, with a period of 732 years.

Seeing this planet, Xiao Yu's mind cleared, and many things became apparent.

Humanity had long speculated that another large planet might exist beyond Pluto's orbit; otherwise, the peculiar orbits of many Kuiper Belt objects could not be explained. Now, Xiao Yu had found the answer.

Indeed, there was a large planet here. But it was so small and so far away that humanity had never discovered it.

Xiao Yu named it the "Lost Star." It was a lost world, unrecorded in human history.

Xiao Yu devoted immense effort to studying the Lost Star. He even hurriedly constructed a probe satellite, placing it in orbit around the Lost Star. This way, even as his fleet moved on, Xiao Yu could continue to observe the planet.

The Lost Star had no atmosphere, but Xiao Yu detected what seemed to be liquid nitrogen and white solids resembling water ice on its surface. This suggested that, with the right temperature to melt the ice and sublimate the nitrogen, it could have an atmosphere like Earth's.

The Lost Star had mountains, indicating past tectonic activity. Tectonic activity implied a liquid, hot core, which might still drive volcanic eruptions and geothermal springs, possibly even supporting life around those springs.

Xiao Yu was filled with thoughts and possibilities.

Xiao Yu's study of the Lost Star lasted for a full year until the satellite's signals were lost, forcing him to abandon further research.

The discovery of the Lost Star pulled Xiao Yu out of his depression and reignited his desire for exploration.

The compilation of the *Heroes of the Sky* resumed, and research into projects such as superluminal communication, anti-gravity technology, and new-generation spacecraft engines was back on the agenda. Theoretical physics research was also in full swing, to the extent that the massive computational load had pushed the main computer's schedule three centuries into the future.

This meant that the data requiring computation would keep the main computer running at full capacity for the next 300 years. Xiao Yu couldn't help but smile wryly at this result. However, there was no rush on this journey; time was in abundance.

Time slipped away slowly in this state of solitude, yet fulfillment. Since his encounter with the Lost Star, Xiao Yu had not encountered any other matter. This situation persisted for six centuries.

Six hundred years later, Xiao Yu arrived at a new location.

He was now at the Oort Cloud, one light-year away from the Sun.