That evening, after everyone had savored the Southern Island to their heart’s content, the entire group decided to stay overnight.
Taking advantage of the opportunity, Jin gathered everyone after dinner to explain the current situation regarding the long-period planet. Since Martha and Lishia were not yet aware of the details, he started with a basic summary.
"A certain celestial body is approaching from the depths of space. At this rate, it will pass close to Ars around October 20th."
"Wait, what?"
"...Jin, what are you talking about?"
For Lishia and Martha, who couldn't quite grasp the magnitude of the situation, Jin used a magi-screen to provide a painstaking, step-by-step explanation.
"...Well, I think I get the gist of it now," Martha said, seemingly accepting the news as just another one of Jin’s extraordinary circumstances.
"...Phew... It sounds like we’re in the middle of a major crisis..." Lishia added, showing a sense of alarm appropriate for the situation.
"Regarding the details..." Jin reset the conversation. "According to Jack on Uni, the planet is about to pass near the fifth planet. There’s a possibility that their mutual gravitational pull will cause its orbit to shift."
"Hmm. The real issue is where it shifts to," Toa said, his brow furrowing slightly.
"It would be one thing if it moved further away from Ars, but if it shifts closer, it could become quite dangerous," Saki agreed.
"Can’t we do something with your spaceship, Jin? Like, get close and intervene?" Saki suggested.
"It’s not that simple..."
The distance between Ars and the fifth planet was roughly 900 million kilometers. The cruise speed of Jin’s spaceship was approximately 200 kilometers per second. At that rate, it would take about 52 days to reach the area, making it impossible to intercept the planet before its closest approach.
"It’s... it’s really that far away? Space is truly immense." Saki stared off into the distance, her expression slightly vacant.
"Wait! That means the long-period planet is moving faster than your spaceship?"
"If we’re comparing it to our cruise speed, yes," Jin explained. He added that while the ship could go faster, doing so carried extreme risks. "At those speeds, colliding with even a tiny pebble would be catastrophic."
He also speculated that the surface of the long-period planet was likely incredibly rugged and unstable.
"As it gets closer to the Sun, Celane, I expect it will accelerate even more. It might eventually reach speeds of 400 kilometers per second."
For comparison, Halley's Comet reached about 55 kilometers per second near its perihelion, making this speed staggering. It was closer to the 375 kilometers per second reached by Comet ISON during its solar approach.
"For now, there isn’t much I can do personally... That said, I’m continuing observations and keeping the spaceship in peak condition."
"I see. Jin, just how large is this long-period planet?" Reinhard asked.
"Ah, it’s roughly the same size as Ars."
"That’s quite large," Reinhard remarked.
"Exactly. Trying to manage something that massive is a daunting task." Jin was effectively answering Saki’s earlier question about whether he could "do something."
"I suppose so. Even for you, Jin, destroying an entire planet is out of the question..."
To put it in perspective, according to calculations for destroying an Earth-sized planet—a concept often seen in sci-fi films—one would need 2.25 × 10³² Joules of energy. That would require converting 2.5 × 10¹⁵ kilograms of mass entirely into energy. For further reference, that is roughly equivalent to seven days' worth of the Sun's total energy output.
"No magi reactor could ever produce that kind of energy..."
"True..."
Jin’s words were met with a chorus of somber agreement.
"Space is just... on a different scale entirely. It makes humans seem so small," Toa whispered, his voice tinged with emotion.
To dispel the heavy atmosphere, Jin spoke up again.
"Well, let’s leave the gloom and doom for now. I want to hear from Saki and Goose. What did you two find?"
The pair had spent the day trekking into the interior of Electra Island in search of rare specimens.
"Well, the trees with the black sap were already reported, so we’ll skip those. We did find several varieties of herbs that look like they’d make excellent spices."
"Heh, the Land unit with us performed a quick Analyze, so we’re fairly certain they aren’t toxic," Saki added with a chuckle.
"Now that’s interesting." Hearing about spices on a Southern Island made Jin lean forward.
"I hope you’ll take them back and research them properly." Saki looked at him with expectant eyes, likely hoping for the development of new flavors.
Jin, too, was pleased by the prospect of expanding his spice rack and agreed immediately. While he wasn't a culinary professional, he knew enough to appreciate the value of spices. He had already discovered or implemented versions of cinnamon, pepper, chili peppers, and turmeric, but he always wanted more. The eight varieties Saki and Goose had brought back were more than enough to pique his interest.
"Thank you. I’ll study them thoroughly and let you know as soon as I have results."
"I’m looking forward to it."
"Oh, and we found one more interesting tree," Goose added. "The wood is incredibly light. It likely grows very fast, though its structural strength is probably low."
Looking at the sample Goose presented, Jin felt a surge of recognition. "It’s balsa."
"Balsa?"
"Yes. As far as I know, it’s the lightest wood in the world. In my previous world, it was frequently used for model making and similar crafts."
Since everyone present knew Jin was from another world, his explanation didn't surprise them.
"I see. Balsa, huh? It sounds like it has potential."
"Yeah. It’s fast-growing and light, so..."
"It could be used for ships, couldn't it, Jin?" Marcia’s voice rang out, full of excitement. She had been quiet during the talk of planets and physics, but she came alive at the mention of shipbuilding materials.
"Exactly. For instance, if you used it to create buoyancy compartments, the ship would be much harder to sink even if the hull was breached."
"Yeah! It would be perfect for small boats."
"Since it’s soft, we’d probably need to sheathe it in a different material," Rodrigo added, already brainstorming alongside his daughter.
The first day of their visit to the Southern Island ended on a productive note.
Late that night, after everyone had retired to their quarters.
Jin and Elsa were relaxing in their bedroom aboard the Azuma.
"About what we discussed earlier..." Elsa, who had been gazing out the window at the sea, turned back to Jin. "What do you think will happen with the long-period planet?"
"Hmm. There’s still too little data to make a definitive call. I’d like at least another two weeks of observation."
The approaching planet had left Elsa with a lingering sense of unease. Given the scale of the threat, it was only natural.
"...But..."
"Hmm?"
"I believe that you’ll find a way, Jin-nii. I trust you."
"Haha, thanks, Elsa." Jin pulled her close, resting his hand on her shoulder, and dimmed the lights. "I’ll have to make sure I don't let you down."
Outside the window, the moonlight cast a pale, gentle glow across the room.