Li Qingsong knew that bright nebulae were divided into emission nebulae and reflection nebulae according to their different types of luminescence. Emission nebulae are nebulae that emit light of their own. Usually, the interstellar dust molecules that make them up are ionized by massive celestial bodies, which then release light of various colors. For example, the Eagle Nebula has a very famous structure inside it, which is the Pillars of Creation. Several huge pillars with a length of tens of light years extend from this nebula. The gas clouds that make up these pillars collapse inward under the influence of external disturbances and their own gravity, and eventually condense into stars. There are dozens or even hundreds of huge stars bred in this stellar nursery. It is precisely because of the birth of these stars that the dust that makes up this nebula is ionized and heated, releasing light. Reflection nebulae are nebulae that do not emit light themselves, but can reflect the light of nearby stars. For example, the Witch Nebula in Orion shines because it reflects the light of Rigel. In addition, there is a more special type, which is the planetary nebula. When a massive star reaches the end of its evolution and a supernova explosion occurs, the materials that make up the star will be thrown into interstellar space by the violent explosion, leaving behind a dense star, a neutron star or a black hole in the center. If it is a neutron star, because it has extremely high radiation, energy and magnetic field, it will "stir" the entire nebula and give it the ability to emit light. The most famous of these is the Crab Nebula.
This massive star is about 6,500 light-years from Earth. It exploded around the Song Dynasty in Earth's time. Although it was so far away, the light when it exploded was still strong enough to be seen even during the day on Earth, and was clearly recorded by the people at the time. But none of these three models of what causes the nebula to glow seem to fit the current situation. The first thing we can rule out about the nebula we observe at this moment is the possibility that it suddenly moved here from somewhere else. Because it can't move that fast. Since it didn't come from somewhere else, it could only be there all along. And if it had always been there, but I hadn't observed it before, then it could only have been a dark nebula. There are three reasons why a dark nebula turns into a bright nebula: 1. It is ionized by its original star; 2. It reflects the light of a nearby star; 3. There is a dense celestial body inside. But all three are impossible. Combined with the information previously obtained from the Blue Tooth prisoners, only one possibility emerged in Li Qingsong's mind. The Bluetuk migration fleet is coming. They were heading towards the solar system from the distant Gliese 625 galaxy. Halfway through their voyage, the fleet entered this dark nebula. The high-speed ions ejected from the spacecraft's engine "stirred" the entire nebula, just like dense celestial bodies or proto-stars, and imparted higher energy to them. As a result, they, which were originally just dark nebulae without the ability to emit light, now began to emit light and were observed by themselves. Li Qingsong had already known that the fleet of the Bluetoke civilization would arrive sooner or later. There was nothing strange or shocking about it. The only thing that shocked Li Qingsong was that the high-speed plasma ejected by a spacecraft's engine had extremely low energy compared to an entire nebula. This nebula is not very large, only about 10 billion kilometers in size, which is enough to cover the entire solar system. Compared with those huge nebulae that are tens or hundreds of light years in size, it is undoubtedly a tiny thing. But the problem is, this is only compared to the rest of the nebula. Compared to intelligent life, it is still unimaginably huge. One spaceship can only "light up" a tiny part of the nebula. To "light up" the entire nebula, how big would the fleet have to be?
At this moment, even if he used the largest-aperture and most advanced telescope he could make at this stage, this nebula was still just a dim bright spot in Li Qingsong's eyes, ordinary and there seemed to be nothing noteworthy about it. But looking at this dim bright spot from afar, Li Qingsong seemed to see endless huge spaceships, a large number of aerospace motherships, a large number of heavy transport ships, and a large number of powerful warships with the power to destroy the world... The jet energy of a spacecraft is limited. When these countless spacecraft are combined, they can light up the entire nebula. What a huge scale. From the Gliese 625 galaxy to the solar system, the distance is more than 20 light years, what a magnificent migration. Compared to... Li Qingsong looked at his migrating fleet. The size of his fleet was already large enough, but compared to the migration of the Bluetuk people, it was like an ant dragging bread crumbs compared to a heavy-loaded train. Li Qingsong deeply felt his own insignificance, and because of his insignificance, he felt tremendous pressure. Just by taking a look at it at this moment, the surging pressure made Li Qingsong almost breathless. I only have two hundred years left. Will I have to face such a powerful enemy after two hundred years? Can I really, truly defeat them? Li Qingsong closed his eyes for a long time, and when he opened them again, there was no more confusion, fear, or worry in his sight, only calmness and determination. He looked at the bright sun quietly and whispered, "If I am the only one left in the solar system, then I will protect our hometown." The huge fleet was still advancing rapidly, and the exploration of the starry sky was still continuing without stopping for a moment. Gradually, the fleet crossed the orbit of Pluto. But unfortunately, Pluto had moved to another place at this moment, and Li Qingsong did not see it. At this point, it has not really entered the inner solar system, because Pluto has long been dismissed from the qualification of a major planet and downgraded to a dwarf planet. The outermost large planet is Neptune. Only when we cross the orbit of Neptune can we be considered to have truly entered the inner solar system. It was another long voyage of more than ten billion kilometers. This time, at a distance of hundreds of millions of kilometers, Li Qingsong used a telescope to see the blue figure of Neptune, which was like the sea. After a journey that lasted several years, covering a distance of more than 10 billion kilometers and hundreds of years in between, at this moment, Li Qingsong finally returned to the inner solar system. The fleet's advance did not stop. Apart from releasing some probes to Neptune, Li Qingsong did not make any stops. His target was always clearly aimed at the largest planet in the entire solar system, Jupiter, in front of him.