Everything You Need to Know About Our Solar System

Along with the holiday that the series brought usarticles about how SpaceX is going to colonize Mars, we completely forgot to talk about the place where all this will happen: the solar system. In truth, very few people are fully aware of how our planetary system works. And since we are about to find ourselves in an era when spacecraft will plow through space (no jokes), it's time to engage in space educational program.

The Universe is a very large place in which wehuddled in a small corner. It is called the Solar System and is not only a tiny fraction of the Universe known to us, but also a very small part of our galactic environs - the Milky Way galaxy. In short, we are a point in the boundless cosmic sea.

However, the solar system remainsa relatively large place in which (so far) many secrets are hidden. We have only recently begun to study closely the hidden nature of our small world. In terms of studying the solar system, we barely scratched the surface of this box.


  • 1 Understanding the Solar System
  • 2 The structure and composition of the solar system
  • 3 Sun and planets
  • 4 The formation and evolution of the solar system
  • 5 Inner Solar System
  • 6 Outer Solar System
  • 7 Trans-Neptune Region of the Solar System
  • 8 Oort Cloud and Farther Regions
  • 9 Solar System Research

Understanding the Solar System

With few exceptions, before the era of modernIn astronomy, only a few people or civilizations understood what the solar system is. The vast majority of astronomical systems postulated that the Earth is a stationary object around which all known celestial objects revolve. In addition, it was significantly different from other stellar objects that were considered ethereal or divine in nature.

Although in the days of ancient and medievalDuring the period there were some Greek, Arab and Asian astronomers who believed that the Universe was heliocentric (that is, that the Earth and other bodies revolve around the Sun) only when Nikolai Copernicus developed a mathematical predictive model of the heliocentric system in the 16th century, this idea was widely adopted.

Galileo (1564 - 1642) often showed people how to use a telescope and observe the sky at St. Mark's Square in Venice. Please note that in those days there was no adaptive optics.

During the 17th century, scholars like Galileo Galilei,Johannes Kepler and Isaac Newton developed an understanding of physics, which gradually led to the acceptance that the Earth revolves around the Sun. The development of theories like gravity has also led to the realization that other planets obey the same physical laws as the Earth.

The widespread use of telescopes has also ledto a revolution in astronomy. After Galileo discovered the moons of Jupiter in 1610, Christian Huygens discovered that Saturn also had moons in 1655. New planets (Uranus and Neptune), comets (Halley's comet) and the asteroid belt were also discovered.

By the 19th century, three observations made by threeindividual astronomers determined the true nature of the solar system and its place in the universe. The first was made in 1839 by the German astronomer Friedrich Bessel, who successfully measured the apparent shift in the position of a star, created by the movement of the Earth around the Sun (stellar parallax). This not only confirmed the heliocentric model, but also showed a gigantic distance between the Sun and the stars.

In 1859, Robert Bunsen and Gustav Kirchhoff(German chemist and physicist) used the newly invented spectroscope to determine the spectral signature of the Sun. They found that the Sun consists of the same elements that exist on Earth, thereby proving that the earthly firmament and the heavenly firmament are made of the same matter.

Then father Angelo Secchi is an Italian astronomer andDirector of the Pontifical Gregorian University - compared the spectral signature of the Sun with the signatures of other stars and found that they are almost identical. This convincingly showed that our Sun consists of the same materials as any other star in the Universe.

Further apparent discrepancies in orbitsexternal planets led the American astronomer Percival Lowell to the conclusion that beyond the borders of Neptune should lie "planet X". After his death, Lowell Observatory conducted the necessary research, which ultimately led Clyde Tombo to the discovery of Pluto in 1930.

In 1992, astronomers David K. Jevitt from the University of Hawaii and Jane Luu from the Massachusetts Institute of Technology discovered a trans-Neptune object (TNO), known as (15760) 1992 QB1. He entered a new population known as the Kuiper belt, which astronomers have long talked about and which should lie on the edge of the solar system.

Further study of the Kuiper belt at the turncenturies led to additional discoveries. The discovery of Eris and other “plutoids” by Mike Brown, Chad Trujillo, David Rabinovich and other astronomers led to a fierce discussion between the International Astronomical Union and some astronomers on the designation of planets, large and small.

The structure and composition of the solar system

At the core of the solar system is the sun(star of the main sequence of type G2), which is surrounded by four planets of the Earth group (inner planets), the main belt of asteroids, four gas giants (outer planets), a massive field of small bodies, stretching from 30 a. e. up to 50 a. e. from the Sun (Kuiper belt) and a spherical cloud of icy planetesimals, which is believed to have extended to a distance of 100,000 a. e. from the Sun (Oort cloud).

The sun contains 99.86% of the known mass of the system, andits gravity affects the whole system. Most of the large objects in orbit around the Sun lie near the plane of the Earth’s orbit (ecliptic), and most bodies and planets rotate around it in the same direction (counterclockwise when viewed from the north pole of the Earth). The planets are very close to the ecliptic, while comets and Kuiper belt objects are often at a great angle to it.

On the four largest rotating bodies (gasgiants) accounts for 99% of the remaining mass, with Jupiter and Saturn accounting for more than 90%. The remaining objects of the solar system (including four terrestrial planets, dwarf planets, moons, asteroids and comets) together make up less than 0.002% of the total mass of the solar system.

Sun and planets

Sometimes astronomers informally share this individual regions. The first, the inner solar system, includes four terrestrial planets and an asteroid belt. Behind it lies the outer solar system, which includes four gas giants. Meanwhile, there are also extreme parts of the Solar System, which are considered a separate region containing trans-Neptune objects, that is, objects beyond Neptune.

Most planets in the solar system possesstheir own secondary systems, around them rotate planetary objects - natural satellites (moons). The four giant planets also have planetary rings - thin strips of the smallest particles rotating in unison. Most of the largest natural satellites are in synchronous rotation, being constantly turned by one side to their planet.

The sun that contains almost all of the matterThe solar system is 98% hydrogen and helium. The terrestrial planets of the inner solar system consist mainly of silicate rocks, iron and nickel. Beyond the asteroid belt, the planets consist mainly of gases (hydrogen, helium) and ice - methane, water, ammonia, hydrogen sulfide and carbon dioxide.

Objects away from the Sun are composed mainly ofmaterials with lower melting points. Ice substances make up the majority of the satellites of the giant planets, as well as Uranus and Neptune (which is why we sometimes call them “ice giants”) and numerous objects lying beyond the orbit of Neptune.

Gases and ice are considered volatile substances. The boundary of the solar system, beyond which these volatiles condense, is known as the “snow line,” at 5 a. e. from the sun. The objects and planetesimals in the Kuiper belt and the Oort clouds consist for the most part of these materials and stone.

The formation and evolution of the solar system

The solar system formed 4.568 billionyears ago during the region’s gravitational collapse in a giant molecular cloud of hydrogen, helium and small amounts of heavier elements synthesized by previous generations of stars. When this region, which was supposed to become the solar system, collapsed, the conservation of angular momentum made it rotate faster.

The center, where most of the mass gathered, begangetting hotter and hotter than the surrounding disk. As the shrinking nebula rotated faster, it began to align into a protoplanetary disk with a hot, dense protostar in the center. The planets were formed by the accretion of this disk, in which dust and gas were pulled together and combined to form larger bodies.

Due to the higher boiling point, onlymetals and silicates can exist in solid form close to the Sun and ultimately form the terrestrial planets - Mercury, Venus, Earth and Mars. Since metal elements were only a small part of the solar nebula, the terrestrial planets could not become very large.

In contrast, giant planets (Jupiter,Saturn, Uranus and Neptune) formed beyond the point between the orbits of Mars and Jupiter, where the materials were cold enough so that the volatile Arctic components remained solid (on the snow line).

The ice that formed these planets wasmore numerous than the metals and silicates that formed the inner planets of the earth group, which allowed them to grow massive enough to capture large atmospheres from hydrogen and helium. The remaining garbage that will never become planets has collected in regions like the asteroid belt, the Kuiper belt and the Oort cloud.

Over 50 million years, the pressure and density of hydrogenin the center of the protostar, they got high enough to start fusion. Temperature, reaction rate, pressure, and density increased until hydrostatic equilibrium was reached.

At this moment, the sun became the main starsequence. The solar wind from the Sun created the heliosphere and swept the remaining gas and dust of the protoplanetary disk into interstellar space, ending the process of planet formation.

The solar system will remain practicallythe same as we know it, until the hydrogen in the core of the sun is completely converted to helium. This will happen in about 5 billion years and will mark the end of the main sequence of the life of the sun. At this time, the core of the Sun collapses and the energy output will be much greater than now.

The outer layers of the sun will expand at about 260times wider than the current diameter, and the Sun will become a red giant. The expansion of the Sun is expected to vaporize Mercury and Venus and make the Earth unsuitable for life, since the habitable zone will go beyond the orbit of Mars. In the end, the core will become hot enough to start helium synthesis, the sun will burn helium a little more, but then the core will begin to shrink.

At this moment, the outer layers of the Sun will gospace, leaving behind a white dwarf - an extremely dense object that will have half the original mass of the Sun, but will be the size of the Earth. The ejected outer layers will form a planetary nebula, returning part of the material that formed the Sun into interstellar space.

Inner solar system

In the inner solar system we find"Inner planets" - Mercury, Venus, Earth and Mars - which are named so because they rotate closer to the Sun. In addition to their proximity, these planets have a number of key differences from other planets in the solar system.

To start: the inner planets are solid and earthy, composed mainly of silicates and metals, while the outer planets are gas giants. Inner planets are closer to each other than their outer counterparts. The radius of this whole area is less than the distance between the orbits of Jupiter and Saturn.

As a rule, inner planets are smaller and denser than their counterparts and have a small number of moons. Outer planets have dozens of satellites and rings of ice and stone.

The inner planets of the earth group are composed ofmost of the refractory minerals are like silicates, which form their crust and mantle, and metals - iron and nickel - which lie in the core. Three of the four inner planets (Venus, Earth, and Mars) have significant atmospheres to shape the weather. All are dotted with impact craters and possess surface tectonics, rift valleys and volcanoes.

Of the inner planets, Mercury is the closestto our Sun and the smallest of the planets of the earth group. Its magnetic field is only 1% of the Earth’s, and a very thin atmosphere dictates a temperature of 430 degrees Celsius during the day and -187 at night, because the atmosphere cannot retain heat. It has no satellites and consists mainly of iron and nickel. Mercury is one of the densest planets in the solar system.

Venus, which is about the size of Earth,It has a dense toxic atmosphere that retains heat and makes the planet the hottest in the solar system. Its atmosphere is 96% carbon dioxide, as well as nitrogen and several other gases. Dense clouds within the atmosphere of Venus are composed of sulfuric acid and other aggressive compounds, with a small addition of water. Most of the surface of Venus is marked by volcanoes and deep canyons - the largest over 6400 kilometers long.

Earth is the third inner planet andbest of all studied. Of the four planets of the earth's group, the largest and only Earth has the liquid water necessary for life. The atmosphere of the Earth protects the planet from dangerous radiation and helps to keep valuable sunlight and heat under the shell, which is also necessary for the existence of life.

Like other planets of the earth group, the Earth hasrocky surface with mountains and canyons and a heavy metal core. The atmosphere of the Earth contains water vapor, which helps to moderate daily temperatures. Like Mercury, the Earth has an internal magnetic field. And our moon, the only satellite, consists of a mixture of various rocks and minerals.

Mars is the fourth and last inner planet,Also known as the Red Planet, thanks to oxidized iron-rich materials lying on the surface of the planet. Mars also has a set of interesting surface properties. On the planet is the largest mountain in the solar system (Olympus) 21,229 meters high above the surface and the giant Valles Marineris canyon 4,000 km long and up to 7 km deep.

Most of the surface of Mars is very old andfilled with craters, but there are also geologically new zones. At the Martian poles are polar caps, which decrease in size during the Martian spring and summer. Mars is less dense than the Earth and has a weak magnetic field, which speaks more of a solid core than a liquid.

The subtle atmosphere of Mars led some astronomers to the idea that liquid water existed on the surface of the planet, only evaporated into space. The planet has two small moons - Phobos and Deimos.

Outer solar system

Outer planets (sometimes called Trojanplanets, giant planets or gas giants) - these are huge planets shrouded in gas, having rings and many satellites. Despite its size, only two of them are visible without telescopes: Jupiter and Saturn. Uranus and Neptune were the first planets discovered since ancient times, which showed astronomers that the solar system is much larger than they thought.

Jupiter is the largest planet in our solara system that rotates very quickly (10 Earth hours) relative to its orbit around the Sun (the passage of which takes 12 Earth years). Its dense atmosphere is composed of hydrogen and helium, possibly surrounding the Earth’s core. The planet has dozens of moons, several faint rings and a Great Red Spot - a raging storm that has been holding for 400 years.

Saturn is known for its outstanding ring system -seven well-known rings with well-defined divisions and spaces between them. How the rings formed is not yet entirely clear. Also, the planet has dozens of satellites. Its atmosphere consists mainly of hydrogen and helium, and it rotates quite quickly (10.7 Earth hours) relative to its time of rotation around the Sun (29 Earth years).

Uranus was first discovered by William Herschel in1781 year. The planet’s day runs for approximately 17 Earth hours, and one orbit around the Sun takes 84 Earth years. Uranium contains water, methane, ammonia, hydrogen and helium around a solid core. The planet also has dozens of satellites and a weak ring system. The only device that visited the planet was Voyager 2 in 1986.

Neptune is a distant planet containing water,ammonia, methane, hydrogen and helium and a possible core the size of the Earth - has more than a dozen satellites and six rings. The Voyager 2 spacecraft also visited this planet and its system in 1989 while passing through the outer solar system.

Trans-Neptune Region of the Solar System

More than a thousand were discovered in the Kuiper beltobjects; They also suggest that there are about 100,000 objects larger than 100 km in diameter. Given their small size and extraordinary distance to the Earth, the chemical composition of Kuiper belt objects is rather difficult to determine.

But spectrographic studies of the regionshowed that its members for the most part consist of ice: a mixture of light hydrocarbons (like methane), ammonia and water ice - comets have the same composition. Initial research also confirmed a wide range of colors for Kuiper belt objects, from neutral gray to saturated red.

This suggests that their surfaces are composed ofa wide range of compounds, from dirty ice to hydrocarbons. In 1996, Robert Brown obtained spectroscopic data on KBO 1993 SC, which showed that the surface composition of the object is extremely similar to plutons (and the Neptune-Triton satellite) in that it has a large amount of methane ice.

Water ice has been discovered in several sites.Kuiper belts, including 1996 TO66, 38628 Huya and 2000 Varuna. In 2004, Mike Brown et al. Determined the existence of crystalline water and ammonia hydrate at one of Kuiper’s largest known sites, 50,000 Quaoar (Quavar). Both of these substances were destroyed during the life of the solar system, which means that the surface of the Quavar has recently changed due to tectonic activity or a meteorite fall.

Pluto's company in the Kuiper belt is worthymentions. Kvavar, Makemake, Haumea, Eris and Orc - all these are large icy bodies of the Kuiper belt, some of them even have satellites. They are extremely distant, but still within reach.

Oort Cloud and Farther Regions

The Oort cloud is thought to extend from2000-5000 a. e. up to 50,000 a. e. from the Sun, although some extend this range to 200,000 a. e. This cloud is believed to consist of two regions - the spherical outer Oort cloud (within 20,000 - 50,000 AU) and the disk-shaped inner Oort cloud (2000 - 20,000 AU).

Oort's outer cloud could have trillionsobjects more than 1 km and billions - more than 20 km in diameter. Its total mass is unknown, but - provided that Halley's comet is a typical representation of the external objects of the Oort cloud - you can outline it roughly 3 × 10 ^ 25 kilograms, or five Earths.

Based on the analysis of the last comets, the vastmost objects of the Oort cloud are composed of volatile arctic substances - water, methane, ethane, carbon monoxide, hydrogen cyanide and ammonia. The appearance of asteroids is believed to be explained by the Oort cloud - in the population of objects there can be 1-2% of asteroids.

The first estimates put their mass in the scope of 380terrestrial masses, but an extended knowledge of the distribution of comets from long periods lowered these indicators. The mass of the Oort inner cloud is still not calculated. The contents of the Kuiper belt and the Oort cloud are called trans-Neptune objects, since the objects of both regions have orbits that are further from the Sun than the orbit of Neptune.

Solar System Exploration

Our knowledge of the solar system is seriousexpanded due to the advent of automatic robotic spacecraft, satellites and robots. Since the mid-20th century, we have had the so-called “space era”, when manned and unmanned spacecraft began to explore planets, asteroids and comets of the internal and external solar systems.

All the planets of the solar system have been visited invarying degrees of vehicles launched from Earth. During these unmanned missions, people were able to get photos of the planets. Some missions even allowed to "try" the soil and atmosphere.


The first man-made object sent tospace, was the Soviet Sputnik-1 in 1957, successfully circling the Earth and collecting information about the density of the upper layers of the atmosphere and ionosphere. The US Explorer 6 probe, launched in 1959, was the first satellite to take Earth images from space.

Robotic spacecraft alsorevealed a lot of significant information about the atmospheric, geological and surface features of the planet. The first successful probe flying past another planet was the Soviet one, the Luna-1 probe, which accelerated with the help of the moon in 1959. The Mariner program has led to many successful planetary flights, the Mariner 2 probe visiting Venus in 1962, the Mariner 4 Mars probe in 1965 and the Mariner 10 Mercury probe in 1974.

By the 1970s, probes were sent to otherplanets, starting with the mission "Pioneer 10" to Jupiter in 1973 and "Pioneer 11" to Saturn by 1979. Voyager probes conducted a grand tour of other planets after launch in 1977, both probes passed Jupiter in 1979 and Saturn in 1980-1981. Voyager 2 then came close to Uranus in 1986 and to Neptune in 1989.

Launched on January 19, 2006, the NewHorizons ”became the first artificial spacecraft to explore the Kuiper belt. In July 2015, this unmanned mission flew past Pluto. In the coming years, the probe will study a number of Kuiper belt objects.

Orbital vehicles, rovers and landersspacecraft began to unfold on other planets of the solar system by the 60s. The Soviet Luna-10 satellite, sent to the lunar orbit in 1966, was the first. It was followed in 1971 with the deployment of the space probe Mariner 9, which circled Mars, and the Soviet probe "Venus-9", which entered the orbit of Venus in 1975.

The Galileo probe became the first artificial satellite,orbiting the outer planet when it reached Jupiter in 1995; it was followed by the Cassini-Huygens mission to Saturn in 2004. Mercury and Vesta were investigated in 2011 by the MESSENGER and Dawn probes, respectively, after which Dawn visited the orbit of the dwarf planet Ceres in 2015.

The first probe that landed on another bodyThe solar system was the Soviet "Luna-2", which fell on the moon in 1959. Since then, probes landed or fell on the surface of Venus in 1966 (Venus-3), Mars in 1971 (Mars-3 and Viking-1 in 1976), asteroid Eros 433 in 2001 (NEAR Shoemaker) and Saturn’s satellite Titan (Huygens) and comet Tempel 1 (Deep Impact) in 2005.

The Curiosity rover made this mosaic self-portrait with the MAHLI camera while on a flat sedimentary rock.

Today, only two solar worldssystems, the Moon and Mars, were visited by mobile rovers. The first robotic rover to land on another body was the Soviet Lunokhod-1, which landed on the moon in 1970. In 1997, the Sojorner landed on Mars, which traveled 500 meters on the planet's surface, followed by Spirit (2004), Opportunity (2004), Curiosity (2012).

Manned space missions began at the beginning50s, and two superpowers, the USA and the USSR, which were tied in a space race, had two focus points. The Soviet Union focused on the Vostok program, which included sending manned space capsules into orbit.

The first mission - “Vostok-1” - took place on April 121961, the first man - Yuri Gagarin - went into space. On June 6, 1963, the Soviet Union also sent the first woman into space - Valentina Tereshkova - as part of the Vostok-6 mission.

In the US, the Mercury project was initiated with the samethe goal of putting the capsule with the crew into orbit. On May 5, 1961, astronaut Alan Shepard went into space with the Freedon 7 mission and became the first American in space.

After the programs "East" and "Mercury"ended, the focus of both states and space programs turned out to be the development of a spacecraft for two or three people, as well as long space flights and extra-space activities (EVA), that is, the astronauts going out into space in autonomous spacesuits.

As a result, the USSR and the USA began to developown programs "Sunrise" and "Gemini". For the USSR, this included the development of a capsule for two to three people, and Gemini focused on the development and expert support necessary for a possible manned flight to the moon.

These last efforts led July 21, 1969 toApollo 11 mission, when astronauts Neil Armstrong and Buzz Aldrin became the first people to walk on the moon. As part of this program, five more lunar landings were carried out, and the program brought many scientific premises from Earth.

After landing on the moon, the American spotlightand Soviet programs began to shift toward the development of space stations and space shuttles. For the Soviets, this resulted in the first manned orbital stations dedicated to space research and military intelligence, known as the Salyut and Almaz space stations.

The first orbital station to accommodatemore than one crew, became NASA's SkyLab; it successfully accommodated three crews from 1973 to 1974. The first real settlement of people in outer space was the Soviet Mir station, which was consistently occupied for ten years, from 1989 to 1999. It was shut down in 2001, and its follower, the International Space Station, has since maintained the constant presence of people in space.

US space shuttles debuting in 1981year, became and remain at the moment the only reusable spacecraft that have successfully completed many orbital flights. Five shuttles built (Atlantis, Endeavor, Discovery, Challenger, Columbia and Enterprise) flew a total of 121 missions until the program was closed in 2011.

During its history of operation, two suchapparatus died in disasters. These were the Challenger crash, which exploded on take-off on January 28, 1986, and Columbia, which collapsed upon re-entering the atmosphere on February 1, 2003.

What happened next, you know very well. Peak 60s gave way to a brief study of the solar system and, in the end, decline. Perhaps very soon we will get continued.

All mission information received during missionsgeological phenomena or other planets - about mountains and craters, for example - as well as about their weather and meteorological phenomena (clouds, dust storms and ice caps) led to the realization that other planets are essentially experiencing the same phenomena as the Earth. In addition, all this helped scientists learn more about the history of the solar system and its formation.

Since our study of internal and externalThe solar system is constantly gaining momentum, and our approach to the categorization of planets has changed. Our current model of the solar system includes eight planets (four terrestrial types, four gas giants), four dwarf planets, and a growing number of trans-Neptune objects that have yet to be identified.

Given the enormous size and complexity of the solar system, its study in full detail will take many years. Will it be worth it? Of course.