Chapter 143: The Five-Element Star

As a region they had been deeply fascinated by since childhood, Huafeng and Yunmeng spent the next dozen days or so immersed in a thirst-driven study of astronomy.

Extragalactic Galaxies:
In Copernicus's theory, the notion that stars were merely points of light located on the outermost stellar sphere was impossible.
In 1584, Giordano Bruno proposed that all stars were distant suns.
In the first half of the 18th century, driven by E. Halley's development of stellar proper motion and J. Bradley's scientific estimation of stellar distances, Bruno's conjecture won approval from an increasing number of people.
In the mid-18th century, T. Wright, I. Kant, and J.H. Lambert hypothesized that the stars filling the entire sky and the Milky Way formed a gigantic celestial system. Friedrich Wilhelm Herschel pioneered the sampling statistics method, using a telescope to count stars in a large number of selected regions across the sky as well as the ratio of bright to faint stars. In 1785, he first obtained an oblate, flat map of the Milky Way's structure with ragged contours and the Sun at its center, laying the foundation for the concept of the Milky Way.
Over the subsequent century and a half, H. Shapley discovered that the Sun is not at the center of the Milky Way, J.H. Oort discovered the rotation and spiral arms of the Milky Way, and numerous scientists measured the diameter and thickness of the galaxy, finally establishing the scientific concept of the Milky Way.
In the mid-18th century, Kant and others also proposed that throughout the universe, countless celestial systems like the Milky Way existed.
By 1924, E.P. Hubble confirmed the existence of extragalactic galaxies by measuring the distance to the Andromeda Galaxy using the Cepheid parallax method.

Diameter and Age of the Universe:
The latest research suggests that the diameter of the universe may be 93 billion light-years, or even larger.
The currently observable age of the universe is approximately 13.82 billion years.
Current cosmological theories suggest that the universe may possess a negatively curved shape resembling a saddle. This theory originates from the Big Bang theory, where the entire universe resembles an inflated balloon, and we live on the "surface" of the universe.
Stephen Hawking stated that the shape of our universe might be an incredible geometric figure, closer to surrealist art, much like the graphics created by the Dutch artist Maurits Cornelis Escher.
Hawking's idea is based on string theory, which currently remains a hypothesis and has yet to be verified. If one were to describe the shape of the universe in words, it should globally present a multi-tessellation pattern with infinitely recurring distorted surfaces, where the surfaces interlock like gears, resembling the "Circle Limit IV" pattern created by Cornelis Escher, and also similar to the "Smith Chart" created by American engineer P.H. Smith, embodying the concept of hyperbolic space as a non-Euclidean geometric spatial form.

Hierarchical Structure:
Contemporary astronomical research achievements indicate that the universe is a hierarchically structured, continuously expanding, matter-form diverse, and ceaselessly moving and developing celestial system.
Planets, asteroids, comets, and meteoroids all revolve around the central celestial body, the Sun, forming the Solar System.
Other planetary systems also exist outside the Solar System. Approximately 250 billion sun-like stars and interstellar matter constitute a more colossal celestial system—the Milky Way. The Milky Way has a diameter of about 100,000 light-years, with the Sun located in one of its spiral arms, roughly 26,000 light-years away from the Galactic Center.
Beyond the Milky Way lie numerous similar celestial systems known as extragalactic galaxies, commonly abbreviated as galaxies. Currently, 100 billion galaxies have been observed, and scientists estimate that there are at least 2 trillion galaxies in the universe.
Galaxies congregate into clusters of various sizes called galaxy clusters. On average, each galaxy cluster contains about a hundred galaxies and spans tens of millions of light-years in diameter. Tens of thousands of galaxy clusters have been discovered. A small galaxy cluster consisting of about 40 galaxies, including the Milky Way, is called the Local Group.
Higher-level celestial systems formed by the aggregation of multiple galaxy clusters are called superclusters. Superclusters tend to have oblate shapes, with major axes reaching hundreds of millions of light-years. Typically, a supercluster contains only a few galaxy clusters, and only a minority possess dozens of them.
The supercluster formed by the Local Group and about 50 neighboring galaxy clusters is called the Local Supercluster.

Galaxy Classification:
Galaxies are classified based on sequence numbers reflecting their evolutionary states, allowing them to be roughly divided into five types: elliptical galaxies, lenticular galaxies, spiral galaxies, barred spiral galaxies, and irregular galaxies.

Among the celestial bodies in the Solar System: The Sun accounts for 99.86% of the total mass of the Solar System. With its formidable gravity, it firmly pulls all celestial bodies in the Solar System around itself, keeping them orderly in their orbits without dispersing. Meanwhile, as an ordinary star, the Sun leads its members in an eternal journey around the center of the Milky Way.
The Sun has a radius of 696,000 kilometers, a mass of 1.989 × 10^30 kg, and a core temperature of about 15,000,000 °C.
If a person were to stand on the surface of the Sun, their weight would be 20 times that on Earth.
Based on observational data and theoretical calculations, the modern nebular hypothesis proposes that the primordial solar nebula was a small cloud broken off from a giant interstellar cloud. It began rotating from the very beginning and contracted under its own gravity, forming the Sun in the central region while the outer parts evolved into a circumstellar disk, from which planets later formed. At present, different schools of thought exist regarding the modern nebular theory, with many disparities among them awaiting further research and confirmation.
Venus is the second planet from the Sun and shines second only to the Moon in the night sky.

There is no water on Venus, and its atmosphere suffers from severe oxygen deficiency, with carbon dioxide comprising over 97%. The air is shrouded in a thick layer of concentrated sulfuric acid clouds ranging from 20 to 30 kilometers deep, and surface temperatures never drop below 400 °C, making it a truly "purgatorial" world. The atmospheric pressure at the surface of Venus is 90 times that of Earth, equivalent to the pressure at a depth of 900 meters in Earth's oceans.
The atmosphere of Venus is primarily composed of greenhouse gases such as carbon dioxide. A runaway greenhouse effect is the main reason behind Venus's extreme climate. Because Venus lacks an intrinsic magnetosphere for protection, the tremendous energy released by magnetic reconnection in its induced magnetosphere heats the Venusian atmosphere, accelerating its escape. The scientific community believes that this atmospheric escape caused Venus to lose its water while becoming enveloped in a dense, carbon-dioxide-rich atmosphere, thereby resulting in a severe greenhouse effect.
Jupiter is the fifth planet from the Sun and the largest, with a mass twice that of all other planets combined (318 times that of Earth) and a diameter of 142,987 km. It is a gas giant with no solid surface, composed of 90% hydrogen and 10% helium (by atomic number ratio; 75/25% by mass ratio), along with trace amounts of methane, water, ammonia, and "rock." This composition is very similar to that of the primitive solar nebula from which the entire solar system formed.
Jupiter likely possesses a rocky core with a mass equivalent to 10 to 15 Earths. Surrounding the core is the primary reservoir of planetary matter, existing in the form of liquid hydrogen.
Liquid metallic hydrogen consists of ionized protons and electrons (similar to the interior of the Sun, though at a much lower temperature). Jupiter has a total of 67 moons.
Ordered by their distance from Jupiter's center from closest to farthest, they are: Metis, Thebe, Amalthea, Adrastea, Io, Europa, Ganymede, Callisto, Sinope, Himalia, Lysithea, Elara, Ananke, Carme, Pasiphae, and Sinope (Note: actual ordering variants adjusted to narrative flow).
Mercury is the planet closest to the Sun. With a radius of approximately 2,440 kilometers, it is the smallest of the eight planets. Mercury experiences extreme diurnal temperature variations, reaching 430 degrees Celsius during the day and dropping to about minus 170 degrees Celsius at night, making it the planet with the largest temperature range among the eight planets of the Solar System. Mercury's exosphere is extremely thin, composed of atoms and ions from its surface and the solar wind. Scientists have confirmed that Mercury's surface is rich in carbon, believing that carbon is the reason for its dark appearance, with surface rocks composed of low weight-percentage graphitic carbon.
Mars is Earth's close neighbor and the fourth planet from the Sun. With a diameter of 6,794 km, its volume is 15% of Earth's and its mass is 11% of Earth's. The surface of Mars is a desolate world, with carbon dioxide making up 95% of its air. The Martian atmosphere is extremely thin, with a density less than 1% of Earth's atmosphere, rendering it completely incapable of retaining heat. This results in extremely low surface temperatures that rarely exceed 0 °C, and nocturnal minimums plummeting to -123 °C.
Mars is known as the Red Planet because its surface is covered in oxides, giving it a rust-red appearance. Most of its surface consists of vast deserts containing abundant red oxides, along with ocher gravel plains and solidified lava flows. Violent winds frequently sweep across Mars, kicking up dust to form mega-dust storms capable of engulfing the entire globe. Each dust storm can last for several weeks. The polar ice caps and the Martian atmosphere contain water. Exploration data gathered from the Martian surface proves that in ancient times, Mars possessed liquid water in extraordinarily large quantities.
Saturn is the sixth planet from the Sun, with a diameter of 120,536 km and a volume second only to Jupiter's. It is composed primarily of hydrogen, with small amounts of helium and trace elements. Its inner core consists of rock and ice, surrounded by multiple layers of metallic hydrogen and gases. Earth is 1.3 billion kilometers away from Saturn.
Saturn's gravity is 2.5 times stronger than Earth's, capable of exerting gravitational pull on other planets in the Solar System, keeping Earth in an elliptical orbit and maintaining an appropriate distance from the Sun suitable for the propagation of life. A 20-degree tilt in Saturn's orbit would bring Earth's orbit closer to the Sun than Venus's, while simultaneously causing Mars to be completely ejected from the Solar System.
Saturn is the only known planet with a density less than water; if it were placed in a gigantic bathtub, it would float. Saturn features a massive magnetosphere and a tempestuous atmosphere, with wind speeds near the equator reaching up to 1,800 kilometers per hour. Among its 31 orbiting moons, Titan is the largest—larger than Mercury and the Moon—and is also the only moon in the Solar System with a dense atmosphere.