Most celestial bodies orbiting the Sun and the mass is primarily concentrated in 8 planets with nearly circular orbits and orbital planes that closely align with each other, referred to as the ecliptic plane. What is the Solar System? This is certainly a question that sparks interest, curiosity, and imagination for many people.
What is the Solar System?
“Solar System” (Thái Dương Hệ) is “a planetary system with the Sun at its center and celestial bodies within the gravitational influence of the Sun”, all of which formed from the collapse of a giant molecular cloud about 4.6 billion years ago.
Our Solar System.
What is the Structure of the Solar System?
The four inner terrestrial planets include: Mercury, Venus, Earth, and Mars – they are also known as rocky planets because they are primarily composed of rock and metal. The four outer gas giants have significantly larger masses compared to the four inner planets.
The two largest planets, Jupiter and Saturn, are mainly composed of helium and hydrogen and are referred to as gas giants, while the two outermost planets, Uranus and Neptune, primarily consist of ice, such as water, ammonia, and methane, and are sometimes classified as ice giants.
There are six planets and three dwarf planets that have natural satellites orbiting them. These satellites are referred to as “Moons”, named after the Moon of Earth. Each outer planet also has planetary rings containing dust, particles, and small objects orbiting around them.
The Solar System also contains two regions filled with smaller celestial bodies. The asteroid belt, located between Mars and Jupiter, has a composition similar to rocky planets, primarily consisting of rock and metal. Outside Neptune’s orbit lies trans-Neptunian objects, which are primarily composed of ice such as water, ammonia, and methane.
Between these two regions are five notable celestial bodies, Ceres, Pluto, Haumea, Makemake, and Eris, which are deemed large enough to have a spherical shape under their own gravitational influence and are classified as dwarf planets by astronomers.
Additionally, there are thousands of smaller celestial bodies varying in size, such as comets, centaurs, and interstellar dust… they move freely between these two regions. The Sun emits streams of plasma, known as solar wind, which creates a stellar wind bubble in the interstellar medium called the heliosphere, extending to the outskirts of the scattered disk. The hypothetical Oort cloud, believed to be the source of long-period comets, may exist nearly 1,000 times further than the heliosphere.
The primary celestial body in the Solar System is the Sun, a G2 main-sequence star that contains 99.86% of the entire system’s mass and dominates with its gravitational force. The four gas giants collectively account for 99% of the remaining mass, with the mass of Jupiter combined with Saturn making up over 90% compared to all other celestial bodies.
Most large celestial bodies have orbital planes closely aligned with the Earth’s orbital plane, known as the ecliptic plane. The orbital planes of the planets are very close to the ecliptic plane, while comets and objects in the Kuiper belt often have orbital planes inclined at a large angle compared to the ecliptic plane.
All planets and most other celestial bodies orbit the Sun in the same direction as the Sun’s rotation (counterclockwise when viewed from above the Sun’s north pole). However, there are some exceptions, such as Halley’s Comet, which orbits in the opposite direction.
Most large celestial bodies have orbital planes closely aligned with the Earth’s orbital plane, known as the ecliptic plane.
The overall structure of regions in the Solar System is illustrated in the adjacent diagram, which includes the Sun, four relatively small inner planets surrounded by a belt of rocky asteroids, and four gas giants surrounded by the Kuiper belt containing icy celestial bodies. Astronomers sometimes informally divide the structure of the Solar System into distinct regions.
In the Solar System, the orbits of the planets are nearly circular, while many comets, asteroids, and Kuiper belt objects have very flat elliptical orbits. The actual distances between the planets are vast; however, many illustrations of the Solar System depict the orbital distances of the planets as equal.
In reality, for planets or belts located further from the Sun, the distance between their orbits is greater. For instance, Venus is about 0.33 astronomical units (AU) away from the Sun compared to Mercury, while Saturn is 4.3 AU away from Jupiter, and Neptune is 10.5 AU away from Uranus.
Numerous efforts have been made to determine the relationship of distances between the orbits of the planets (for example, the Titius-Bode law), but no theory has been widely accepted.
Most planets in the Solar System have their own secondary systems.
Most planets in the Solar System possess their own secondary systems, which include natural satellites or planetary rings orbiting around the planets. These satellites are also referred to as Moons. Two natural satellites, Ganymede of Jupiter and Titan of Saturn, are even larger than Mercury.
The gas giants such as Jupiter, Saturn, Uranus, and Neptune, as well as a satellite of Saturn, have planetary rings that are thin bands containing small particles orbiting around them.
Most of the largest natural satellites are synchronized, always presenting one hemisphere towards their parent planet. The inner celestial bodies are primarily composed of rock, commonly referred to as compounds with high melting points, such as silicates, iron, or nickel, and have remained solid since the protoplanetary nebula stage.
Most of the largest natural satellites are synchronized, always presenting one hemisphere towards their parent planet.
Jupiter and Saturn are primarily composed of gas, with astronomical terminology referring to materials with extremely low melting points and high vapor pressures such as hydrogen, helium, and neon, which always exist in gaseous phases in nebulae. Ice, such as water, methane, ammonia, hydrogen sulfide, and carbon dioxide, has melting points reaching several hundred Kelvin, while their phases depend on the surrounding pressure and temperature.
They can be found in the form of ice, liquid, or gas in many places throughout the Solar System, while in nebulae, they exist only in solid (ice) or gaseous states. Icy substances are primary components on the moons of gas giants, as well as constituting a significant part of the composition of Uranus and Neptune (referred to as “ice giants”) and in many small objects located beyond Neptune’s orbit. Gases and ices in astronomy are collectively referred to as volatiles.
