The solar system is a planetary system formed by the Sun and the celestial bodies that orbit around it, including our planet Earth. There are many other solar systems in the universe.
Planetary System vs. Solar System
A planetary system is formed by one or several central stars and different bodies that revolve around it. Scientists discovered that stars are accompanied by opaque bodies (planets, dwarf planets, satellites), by dust and gas. This set is called a planetary system.
How Many Solar Systems are in Our Galaxy?
Astronomers have found more than 500 solar systems and continue to discover new ones every year. It is estimated that there may be tens of billions of solar systems in our galaxy.
Our planetary system is called the Solar System because the largest star is the only star that integrates it: The Sun.
How Did the Solar System Form? The Origin of the Solar System
According to current theories, the solar system originated 4.6 billion years ago from a cloud of gas and dust. Due to the effect of gravity, the gas cloud gradually joined and formed objects.
The accumulated gas became hotter, giving rise to the Sun through nuclear fusion. It is a transformation of the nuclei of atoms that release large amounts of heat and light. This is how stars are born. The sun is a star. The gas that came together also gave rise to smaller stars that do not emit light: the planets.
What are the Theories for the Origin of the Solar System?
Geocentric Model for kids
Over time the theories of the origin of the universe were modified. In ancient Greece, Aristotle believed that the Earth was located at the center of the universe and that the sun, moon, and planets revolved around it in a circular fashion.
This model of the solar system (in which the earth was in the center) was called the Geocentric Model. (Geo: earth, Centrum: center). This idea was reinforced because from the planet earth it was seen that the sun rose and set on the horizon. Two thousand years ago, Claudius Ptolemy, an Egyptian astronomer, held the same thing.
Heliocentric Model for kids
Nicholas Copernicus (1473-1543), was a Polish astronomer who, after his research, published his book “On the Revolutions of the Celestial Stars” (De revolutionibus orbius celestium). This model placed the Sun at the center of the Solar System.
Galileo Galilei later called it the heliocentric model (Helios from the Greek: Sun and Centrum from the Latin: Center) in which the Earth and the planets revolved around the Sun. It is the model that we accept today, although at the time it was highly resisted. Until then they only knew of five planets.
Kepler’s Laws of Planetary Motion
And the astronomer Johannes Kepler in 1609 discovered that the planets rotated elliptically (elliptical or oval circles) and not round as was believed until then. And that the time it takes for a planet to go around the sun will be greater the further away it is.
How to Teach the Solar System
The Solar System is located in a galaxy called the Milky Way that contains 100 billion stars. It is made up of eight planets, dwarf planets, satellites, asteroids, and comets. The planets that revolve around the Sun are: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune.
What is a Galaxy?
A galaxy is a group of billions of stars, held together by mutual gravitational attraction. Astronomers discovered galaxies by looking through telescopes.
Galaxies have different shapes, spiral, ellipse, irregular. The Solar System belongs to the Milky Way, which is a spiral galaxy made up of 400 billion stars.
Components of the Solar System
What is the Sun?
The Sun is the largest star in the Solar System and the closest star to Earth. It is located 150 million kilometers from Earth. It is the main star and represents 99% of the size of this entire planetary system. Due to its great force of gravity, the rest of the celestial bodies revolve around it. It is our source of energy, it allows life on Earth and it is located in the center of the Solar System. If we compare it with the rest of the stars in the universe, it has a medium size. But it is much larger than the rest of the members of the Solar System. It was formed 4,600 years ago.
Structure and Characteristics of the Sun
The sun is a more or less spherical body with an irregular surface on which sunspots can be seen. It is mainly composed of a gas called hydrogen and helium in lesser proportion.
Parts of the Sun
• Nucleus of energy that travels in the form of light that reaches the solar surface. The core has high temperatures generated by these gases. Temperatures at the center of the sun reach approximately 17,000.000 ºF.
• Photosphere or grainy solar surface. There temperatures rise to 10,000 ºF
• Solar atmosphere that is divided into the chromosphere and the corona, which is an envelope of gas that emits heat and light.
The Sun’s corona is the outermost part of the Sun’s atmosphere. It is hidden by bright light from the Sun’s surface. During a total solar eclipse, the Moon passes between the Earth and the Sun blocking the bright light from the Sun. Then the white crown can be seen
How does the corona cause solar winds?
The temperature of the corona causes its particles to move at such high speeds that they can escape the Sun’s gravity.
How many Planets are there in the Solar System
What is a Planet?
The word planet derives from the Greek and means “wanderer”. Unlike the stars that are fixed in the sky, the planets move. The International Astronomical Union (IAU) defined in 2006 the planets by the following characteristics:
1. They rotate in elliptical orbits around the Sun and are attracted by the force of gravity on the Sun.
2. They have a spherical shape due to the amount of mass that constitutes them and their own force of gravity.
3. They have no elements in the orbit. Its orbit is said to be clean or clear.
The planets that make up the solar system differ from each other by the presence or absence of atmosphere, color, temperature, the presence of satellites or rings, among others. They are opaque bodies that do not emit light (when they shine, it is because they reflect sunlight).
Solar System: Planets Characteristics
How are planets classified?
The planets classify in various ways. If we take into account the location with respect to the Sun they are: inner and outer planets.
Inner and Outer Planets in our Solar System
They are the four that are closest to the sun, have few satellites (or none) and have a solid surface composed of rocks and metals, which is why they are known as rocky planets. They are Mercury, Venus, Earth and Mars.
They are located further from the sun. They are large if we compare them to Earth. They are called the Gas Giants because they are made of gases. They have rings made up of stones, ice and dust. They have numerous natural satellites. They are Jupiter, Saturn Uranus and Neptune.
Mercury is the smallest and closest to the sun. It has no natural satellites or moons. Its surface is rocky and dry and full of craters that cause the crash of the meteorites that impact because it has no atmosphere. Going around its axis takes 58.64 days. The temperature ranges between 420ºC and -180ºC.
It is the planet that is closest to Earth, similar in size to ours. It is surrounded by a thick atmosphere, which gives it a yellowish color that traps the sun’s heat. The sky of Venus is always full of clouds. It does not have satellites revolving around it. It looks very bright that’s why it is known as “lucero”.
It has an atmosphere made up of nitrogen and oxygen, which filters ultraviolet radiation from the Sun and keeps temperatures stable. There is abundant water in a liquid state, which is why it is known as the “blue planet”. It has only one satellite: The Moon.
Read also: Earth and Space for Students
It is the fourth planet from the sun, it is smaller than the earth, (half the diameter) it is known as the red planet, it is rocky, desert, icy and dusty. It contains frozen water at its poles, and large wind and dust storms. Carbon dioxide predominates in its atmosphere. It has two natural satellites or moons called Deimos and Phobos.
Jupiter is the largest planet of all, the fifth from the sun. It is made up of hydrogen and helium. It has more than 60 satellites or moons. It spins very fast on its axis, which triggers strong storms and sub-zero temperatures.
It is the second largest planet, after Jupiter. It is surrounded by the characteristic rings formed by “bits” of ice and rocks. It has 60 moons, Titan is the largest. Winds on Saturn reach 500 km per hour and temperatures are less than 100 degrees below zero.
Why does Saturn have rings?
Scientists don’t know for sure. The rings we see are made up of chunks of ice and rock. Like Jupiter, Saturn is mostly a big ball of hydrogen and helium.
It is blue-green in color because there is a large amount of methane gas in its atmosphere. Its diameter is four times that of the Earth. It is twenty times further from the Sun than the Earth, so temperatures are below 200ºC below zero. It has at least 27 moons.
Neptune is the last in the Solar System. This planet is very large, 60 Earth planets would fit inside it. It is very cold (220 ºC below zero or -364 ºF) and it looks blue, it is surrounded by thick clouds. It has at least 9 moons.
Other components of the Solar System
In addition to the sun and the planets, there are other important objects in the Solar System such as: Dwarf planets, natural satellites, asteroids, meteoroids and comets.
Natural and Artificial Satellites
Natural satellites are bodies that revolve around a star, usually a planet, and accompany it in its movement around the sun (revolution). They are called natural or also moons, because there are also artificial ones (created by human beings).
How many Moons do other Planets have?
In the Solar System there are more than 150 natural satellites. The planets have different numbers of satellites that are held together by the force of reciprocal gravity.
The Earth has a satellite, the Moon. There are some planets that do not have any, as in the cases of Mercury or Venus.
Mars has two: Deimos and Phobos. And the outer planets have a large number of natural satellites.
Jupiter and Saturn have more than 60 each.
There are various theories about the origin of natural satellites. Some astronomers maintain that they formed together with the planet. Others that are bodies that have been attracted by gravity. Some are believed to be made of rocks and helium. Ganymede (from the Greek Γανυμήδης) is the largest natural satellite of Jupiter and the Solar System, it is also the only one that has a magnetic field.
What is the Moon?
The Moon is the only natural satellite that revolves around the Earth. You can learn more about the Moon and What is the Universe.
The human being has built artificial satellites and has sent them into space to revolve around the Earth collecting information. Artificial satellites are tools placed around the orbit of the Earth or other stars. They have been built by man and their trajectory can be modified.
These satellites can have various shapes (spherical, conical, cylindrical), and they carry instruments of great delicacy, sensitivity and precision. A satellite is launched into space by means of a series of rockets that are fired successively, at different heights, in order to give it the necessary direction and speed.
Once placed in orbit, the artificial satellite travels freely through space. They obtain information and transmit it to Earth. Satellites can have various uses, such as communication, navigation, military affairs, meteorology, study, reconnaissance and earth observation.
What is a Dwarf Planet: Pluto
Dwarf planets are celestial bodies that have the same characteristics as the rest of the planets. They are spherical and revolve around the sun. They are smaller than the planets with less force of gravity. This means that they cannot attract other bodies that “cross” their path, or cannot “expel” them from their path. They are unable to clear their orbit of other stars and share it with asteroids and comets.
Pluto was considered the 9th planet of the Solar System until 2006, when the International Astronomical Union (IAU) decided to move it to the category of dwarf planet.
There are currently 5 dwarf planets in the Solar System: Pluto (previously considered a planet), Ceres (previously considered an asteroid), Eris, Makemake, and Haumea.
What are Asteroids and Comets?
An asteroid is an irregularly shaped rocky and metallic star that revolves around the sun. It cannot be considered a planet due to its small size. Some have moons (satellites) that revolve around them. They can measure from a few hundred meters to kilometers. The largest number of asteroids in the Solar System are found in the Asteroid Belt located between the orbits of Mars and Jupiter.
They are masses of ice, rock and dust that revolve around the sun in very elongated ellipses. When they pass close to the sun, the ice gasifies, forming a long tail that can be seen from Earth.
Movement of the Planets: Rotation and Revolution
Johannes Kepler discovered that the planets do not move in perfect circles, but instead describe orbits that are ellipse-shaped (oval-shaped like an egg). This motion around the sun is called revolution or translational motion.
Also, the planets rotate on themselves. They carry out this movement on their own imaginary axis that crosses the planet from side to side through its center called the axis of rotation. It is called the rotational movement. It resembles the movement of a carousel. Except for Venus and Uranus, the planets rotate counterclockwise.
Apparent Movements of the Stars for Children
When you look at the sky, you can perceive that the stars have a certain displacement, it seems that they move. This is called apparent motion because they seem to move only to our vision and it is not real. In life we say that the sun “sets” or hides, hides, rises and other terms that would not really be correct. Our planet Earth rotates causing the “illusion” that the stars, both the Sun and the stars, move around. The direction of apparent movement of the stars is always from east to west.
How long is a day on each planet?
The time it takes for the Earth to rotate on its axis is called a day. Each day of rotation corresponds to a day of sunlight and a night of shadows. This calendar day is divided into 24 equal parts called hours.
A year on the different planets does not last the same terrestrial time. The time it takes for the planets to go around the sun one full revolution is one year on that planet. The closer they are to the sun, the shorter the year for that planet.
A year on Earth is the time it takes for the Earth to go all the way around the Sun. Revolution or translational movement of the Earth lasts 365 days and 6 hours.
Tilt of the Earth’s Axis
The terrestrial axis is an imaginary line that is drawn between the two poles, the North Pole and the South Pole. This axis is inclined, it is not vertical. The inclination is almost 24º during its entire trajectory around the sun. The sun illuminates the terrestrial hemispheres in different ways, which is why the sun’s rays reach the Earth’s surface at different angles. Giving rise to the different seasons of the year. When a hemisphere is more exposed and the rays are projected more vertically, they cause higher and warmer temperatures (spring and summer).
The Stars for Children
What is a Star?
Stars are huge spheres of gases, at such high temperatures that they emit large amounts of light and heat into space. From planet Earth we observe them as very bright or we hardly see them at all. This is because they are at different distances.
Constellations are groups of stars. 88 constellations are recognized. They have been given names some you will know: Aries, Taurus, Gemini, Cancer, Leo, Virgo, Libra. Scorpio, Sagittarius, Capricorn, Aquarius and Pisces. Yes! They are the names of the zodiac signs. These zodiac constellations are spread over a circumference. Eclipses form when one star hides another.
How are the Stars for Children
Stars, like the sun, are cosmic bodies that illuminate the universe. They are formed by masses of gases, mainly hydrogen and helium, which generate and emit light. They are at very high temperatures. Although we see them as points of light in the sky, they do not all have the same color. Color varies according to surface temperature. Those of higher temperature (hotter) appear blue or white, and those of lower temperature appear orange or reddish. They are very large, spherical in shape and very far away.
They seem to be fixed, always in the same place in the sky. In reality, the stars are in rapid motion, only they are so far away that their changes in position are seen only across centuries.
The number of stars that astronomers have calculated in the Milky Way is in the hundreds of billions.
Parts of a Star
Astronomers differentiate two parts in the stars:
• Main body: compact, which is where the light emerges from. Inside is the core, with very high temperatures.
• Stellar atmosphere: It is gaseous and surrounds the main body.