Tom knew that bright nebulae are divided into emission nebulae and reflection nebulae, depending on their type of luminescence.
Emission nebulae are nebulae that can emit light themselves. Usually, the interstellar dust molecules that make them up are ionized by a huge celestial body, and then release light of various colors.
For example, the Eagle Nebula. There is an extremely famous structure inside this nebula, which is the Pillars of Creation.
Several huge pillars, tens of light-years long, extend from this nebula. The gas clouds forming these pillars collapse inward under the influence of external disturbances and their own gravity, eventually condensing into stars.
Dozens to hundreds of huge stars are born in this stellar nursery. It is precisely because of the birth of these stars that the dust forming this nebula is ionized and heated, and thus emits light.
Reflection nebulae are nebulae that do not emit light themselves but can reflect the light of nearby stars. For example, the Witch Head Nebula in Orion glows by reflecting the light of Rigel.
In addition, there is a more special type, which is the planetary nebula.
When low- to intermediate-mass stars evolve to their end, they shed their outer layers in a gentle ejection, forming a glowing shell around a hot central white dwarf.
If it is a planetary nebula, the ultraviolet radiation from the central white dwarf ionizes the ejected gas, causing it to fluoresce and emit light. Thɪs chapter is updatᴇd by novel·fire.net
The most famous supernova remnant of this type is the Crab Nebula—not a planetary nebula, but a Type II supernova remnant.
This massive star is about 6,500 light-years from Earth. It exploded around the Song Dynasty period in Earth’s history.
Although it was so far away, when it exploded, its light was still so strong that it could be seen even during the daytime on Earth and was clearly recorded by people at that time.
But these three modes of causing nebulae to glow do not seem to fit the current situation.
The possibility that the nebula he observed at this moment suddenly moved here from somewhere else can first be ruled out.
Because its speed of movement cannot be that fast.
Since it didn’t fly over from somewhere else, it can only have been there all along. And if it was there all along, but he hadn’t observed it before, then it could only have been a dark nebula before.
The reasons why a dark nebula turns into a bright nebula are nothing more than those three: first, being ionized by a nascent star. Second, reflecting the light of a nearby star. Third, having a dense celestial body inside.
But none of these three are possible.
Combining the intelligence previously obtained from the Blueprint prisoners, the only possibility emerged in Tom’s mind.
The migration fleet of the Blueprint Civilization has arrived.
They came from the distant Gliese 625 star system toward the Solar System, and halfway through their journey, the fleet entered this dark nebula.
The high-speed ions ejected from the spacecraft’s engines, like a dense celestial body or a nascent star, "stirred" the entire nebula, imparting higher energy to them. As a result, what were originally just dark nebulae, incapable of emitting light, now began to emit light and were observed by him.
The Blueprint Civilization’s fleet would arrive sooner or later; this was something Tom had known for a long time, and there was nothing strange or shocking about it.
The only thing that made Tom feel somewhat shocked was that the high-speed plasma ejected by a single spacecraft’s engine had extremely low energy compared to an entire nebula.
This nebula is not large, only about ten billion kilometers in size, roughly enough to envelop the entire Solar System.
Compared to massive nebulae that are tens or hundreds of light-years in size, it is undoubtedly tiny.
But the problem is, this is only in comparison to other nebulae.
Relative to intelligent life, it is still unimaginably vast.
A single spacecraft can only "light up" a tiny bit of the nebula. To "light up" the entire nebula, how enormous must this fleet be?
At this moment, even using the largest caliber and most technologically advanced telescope he could manufacture, this nebula still appeared as only a dim speck in Tom’s eyes, unremarkable, seemingly with nothing noteworthy.
But gazing at this dim speck, Tom seemed to see an endless stream of massive spacecraft, large numbers of aerospace carriers, heavy transport ships one after another, and powerful warships capable of destroying the world...
The energy ejected by a single spacecraft is limited. When these countless spacecraft combine, they illuminate an entire nebula.
What an enormous scale that is. And what a magnificent migration it is, spanning over 20 light-years from the Gliese 625 star system to the Solar System.
Tom looked at his own migration fleet.
His own fleet’s scale was already quite large. But compared to the Blueprint’s current migration, it was like an ant dragging a breadcrumb compared to a heavy-haul train.
Tom deeply felt his own insignificance. And because of his insignificance, he felt immense pressure.
At this moment, just this one glance, the surging pressure made Tom almost gasp for breath.
He only had a little over two hundred years left. After more than two hundred years, would he have to face such a powerful enemy?
Can I really, really defeat them?
Tom closed his eyes. After a long while, he opened them again, and there was no longer any bewilderment, fear, or worry in his gaze, only calmness and determination.
He quietly gazed at the bright sun and whispered, "If only I am left in the Solar System, then let me protect our homeland."
The massive fleet continued to advance rapidly. The exploration of the starry sky also continued without a moment’s pause.
Gradually, the fleet passed beyond Pluto’s orbit.
However, unfortunately, Pluto was in another location at this moment, and Tom did not see its figure.
At this point, it was not yet considered truly entering the Inner Solar System. Because Pluto had long since been stripped of its major planet status and demoted to a dwarf planet.
The outermost major planet is Neptune.
Only by crossing Neptune’s orbit would they truly enter the interior of the Solar System.
After another long journey of over a billion kilometers, this time, separated by hundreds of millions of kilometers, Tom saw the azure, ocean-like figure of Neptune through his telescope.
After a journey spanning several years, covering a vast distance of over ten billion kilometers, and separated by centuries, Tom finally returned to the Inner Solar System once again at this moment.
The fleet’s advance did not stop.
Aside from releasing some probes to Neptune, Tom made no other stops.
His target was always clearly aimed at the largest planet in the entire Solar System ahead, Jupiter.