The Solar System is a vast network of celestial bodies composed of the Sun, eight planets with their respective moons (150 or so in all), hundreds of asteroids, comets and cometary objects; plus other objects ranging from giant gas planets to minute dust particles.
Solar system first emerged 4.6 billion years ago from a cloud of gas and dust known as a solar nebula.
The Sun
Our solar system’s sun is the core of its lifeforce: an enormous sphere composed of hydrogen and helium which emits vast amounts of energy through nuclear fusion. Astronomers such as Galileo discovered planets orbit them due to gravity; later Einstein created his famous equation E=MC2 to explain how stars could produce so much power.
At approximately 4.5 billion years ago, the Sun began its existence when clouds of gas and cosmic dust collapsed under its gravitational force to form dense centers which eventually formed into cores which over time experienced heat and pressure fluctuations to expand and contract until eventually hydrogen started being converted to helium in its core and release energy which then flowed outward from it into its outer layers as light radiations from there.
At some point in time, hydrogen atoms in the outer layers will fuse to become heavier elements such as carbon and oxygen, creating heavier elements called “heavy elements”, before starting to dissipate into solar wind – sending charged particles hurling towards our sun’s core from outlying areas of burning debris. Once solar wind dissipation has completed, only carbon core will remain; once that process completes itself it will cool down into becoming a white dwarf — dense mass with no further energy production or emission capabilities generating or radiating any energy into space – wherein energy sources must come from externally-generated sources or emitters of energy from outside sources.
The sun’s magnetic field consists of loops of electric current running through its layers. Sunspots form when these magnetic fields come close to its surface, where massive tubes of gas rise from its chromosphere and follow along their lines, creating arches visible from Earth.
The Moon
The Moon remains one of the planets humans have set foot upon, but still holds many mysteries. Scientists have revealed its composition: it is composed of rocky material with a small metallic core, as well as having an atmosphere composed of oxygen, helium, sodium magnesium iron and aluminium molecules. Furthermore, some regions on its surface feature heavier deposits called “mascons” while some places feature bulging areas.
The leading theory for the Moon’s creation suggests it was formed when a Mars-sized planet collided with Earth at an early stage in Solar System development, approximately 4.5 billion years ago. As its debris disintegrated and collected together into less dense material masses, eventually becoming what we now call “the Moon”, its mass congregated into its current shape forming it as we know it today.
Tidal forces gradually reduced the Moon’s spin rate as it orbited Earth, eventually coming to rest where one side always faced away from us, in what’s known as synchronous rotation.
Astronauts first walking on the Moon noted its darker tone due to a lack of atmosphere that diffuses sunlight to cast shadows; instead, sunlight simply reflects off its surface.
One of the more intriguing Moon facts is its magnetic field, though it is significantly weaker than Earth’s. Additionally, some rocky surfaces display remnant magnetism which suggests its former active interior may still exist.
The Planets
The Solar System comprises the Sun, its eight planets and five dwarf planets as well as their hundreds of moons as well as comets and asteroids held in orbit by its powerful gravity field. All these objects orbit around it as part of its complex ecosystem.
Planets were formed 4.6 billion years ago from a cloud of gas and dust known as the solar nebula, when our Sun began its rapid ascension through it. Soon afterwards, a thin disk of gas and dust formed around it; as the Sun moved through this disk, collisions among smaller bodies scattered fragments of rock and ice into major planets which still exist today.
Mercury, Venus, Earth and Mars all possess very thin atmospheres; Jupiter boasts thick clouds while Saturn boasts rings. Uranus and Neptune lie so far away from the Sun that sunlight takes nearly four-and-a-half hours to reach them.
These planets may differ significantly, yet all share one trait in common: they all rotate clockwise around the Sun. One notable exception is Venus, which rotates anti-clockwise. This may be the result of a large collision during early Solar System formation.
Long ago, children were taught there were nine planets in our Solar System–Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune. But in 2006, when Pluto was dethroned from true planet status by being declared a dwarf planet by the International Astronomical Union, eight true planets are now considered true planets; all except Mercury which does not yet possess a moon are being studied in school classes today.
The Dwarf Planets
The Solar System contains eight planets as well as five dwarf planets: Pluto, Ceres, Eris, Haumea and Makemake. Like planets, dwarf planets orbit around the Sun but differ in that their orbit does not clear out space of similar objects like other planets would.
The International Astronomical Union (IAU), which regulates planetary science, defines a dwarf planet as any celestial body which has attained and maintained hydrostatic equilibrium (a nearly circular shape), but has not reached such mass as to clear out its orbit of similarly-sized bodies. According to this definition, Pluto, Ceres, Haumea, Makemake and Eris are officially recognized dwarf planets by IAU.
Pluto and Ceres are among the better-known planets due to being visited by spacecraft. Of the remaining four, three (Makemake, Haumea and Eris) each possess two moons named for one or both daughters – Haumea’s two are even named after them! Makemake has one known by its Hubble Space Telescope nicknamed MK2 that orbits it.
These dwarf planets can be found in the outer regions of our Solar System: in the Asteroid Belt and Kuiper Belt beyond Neptune. A sixth candidate dwarf planet known as Varda or Hygiea remains undecided as to its status; scientists remain uncertain whether its orbit can exist in hydrostatic equilibrium.
Of these stars, three have been visited by spacecraft while seven (Makemake, Haumea, Eris, Gonggong, Quaoar, Sedna and Salacia) possess known satellites which enable us to estimate their masses and densities.
The Comets
Comets are icy balls of rock, dust and water that orbit the Sun. Their composition remains from early Earth-Solar System interactions. If a comet gets close enough to the Sun, its heat may melt some of its ice to release gases which then get carried away by solar wind into its orbit and form a tail up to millions of miles long.
Comet tails consist of two components, the ion tail and dust tail. The former typically extends away from the Sun as an electrically charged gas molecules migrate towards it; the latter often forms as a white trail behind it – both created when close to the Sun for only brief moments of time.
Scientists long assumed that comets were periodic (P 200 years), meaning that they returned to their original orbit every 2000 years or so. But then astronomers discovered non-periodic comets like Hale-Bopp, Hyakutake, and McNaught that do not return in this pattern and instead originate far beyond Neptune where an extensive population of dark and icy objects known as the Kuiper belt can be found.
Astronomer Gerard Kuiper first proposed that this belt comprised an irregular disk of icy comets whose orbits extended approximately half way to the Sun, replenished by smaller populations originating far beyond it; now known as the Oort Cloud; estimates indicate it holds upwards of 10 trillion (1012) comet-like particles which scientists study closely in order to understand more fully its dynamics of early Solar System development.