What is unique about planets - Explore the Universe: Your Guide to Astronomy

Humanity will not remain forever on Earth, but in the pursuit of knowledge and exploration will first cautiously venture beyond the atmosphere, and then conquer the vast expanse of our solar neighborhood.

This website is dedicated to the wonders of our solar system.

A celestial body (also referred to as an astronomical object) is a distinct, cohesive structure held together by gravity. Within our solar system, we have the following celestial bodies:

Astronomers also identify smaller celestial bodies such as dwarf planets, asteroids, comets, meteoroids, and meteors. However, the most significant types of celestial bodies are the planets. They can be further classified as Terrestrial (located closer to the Sun) or Gas Giants (enormous objects found in the outer regions of the system).

Dwarf planets stand apart from their “elder siblings” due to the presence of other celestial objects circling around them and their relatively diminutive size. Currently, there are 5 recognized members in this category: Pluto, Ceres, Erid, Haumea, and Makemake. Between 2017 and 2019, there was speculation that the asteroid Hygeia might also be deemed worthy of inclusion in this esteemed group. Apart from the dwarf planets, our solar system also boasts a variety of other small celestial bodies.

The Sun, an enormous sphere of gas, has a diameter estimated to be 1.392 million kilometers, which is 109 times larger than Earth’s diameter. It comprises 99.87% of the total mass of the solar system.

In astronomical terms, the Sun is categorized as a “yellow dwarf,” indicating that it is relatively small compared to other stars but emits a significant amount of light.

Thermonuclear reactions are responsible for the heat radiated by the star. Within the core of the Sun, hydrogen atoms combine to form helium atoms and release energy. This process, known as the proton-proton cycle, contributes to approximately 98% of the energy generated by the star. Nevertheless, there are additional reactions in which elements like helium, carbon, oxygen, neon, and silicon undergo fusion, resulting in the formation of metals like iron, magnesium, calcium, nickel, as well as other elements like sulfur. Collectively, these processes are referred to as stellar nucleosynthesis.

The impact of the Sun on the surrounding celestial objects is immense. The solar wind, consisting of particles emitted by the star, dominates the space between planets up to a distance of 100-150 astronomical units. It is believed that the gravity of our star influences the orbits of bodies located even light-years away.

The Sun itself undergoes rotation on its axis. Due to its gaseous composition, different layers of the Sun rotate at varying speeds. The equator completes one rotation every 25 days, while the poles take 34 days. Recent research also indicates that the inner regions rotate much faster than the outer shell.

Mercury

Mercury, the planet closest to the Sun and the smallest planet in our solar system, is just a little bit bigger than the Moon. It receives seven times more heat and light than Earth, which means that its surface temperature can range from a scorching +430°C during the day to a freezing -190°C at night. In fact, this temperature difference is the largest of any planet in our solar system.

Interestingly, Mercury has virtually no atmosphere. Scientists believe that this lack of atmosphere could be due to the intense solar radiation that the planet receives, or it could simply be because a planet of this size is unable to hold onto a dense gas envelope.

Because Mercury has a much smaller orbit around the Sun compared to Earth, its year is much shorter – only 88 Earth days. In fact, more than two local years pass in just one day on Mercury. Additionally, since the planet’s axis of rotation is almost not tilted, it does not experience distinct seasons like Earth does.

Venus

Venus, also known as the second planet from the Sun and the closest to Earth, is often referred to as our planet’s “twin” due to its similar size and mass. However, the similarities between Venus and Earth end there.

Venus is enveloped in an incredibly dense layer of clouds, making it impossible to see its surface. The greenhouse effect on Venus causes the planet to heat up to a scorching 480°C, setting an absolute record within our solar system. Additionally, the clouds on Venus release acid rain and only allow 40% of sunlight to penetrate, resulting in a perpetually gloomy atmosphere.

Unlike any other planet, a day on Venus lasts longer than its year, with a duration of approximately 243 Earth days. In contrast, a year on Venus is slightly shorter, lasting about 225 Earth days. Similar to Mercury, Venus does not experience any distinct seasons.

Venus has the ability to reflect sunlight effectively, which gives it a brilliant appearance in the Earth’s sky compared to other planets. This may be the reason why the ancient Romans correlated Venus with the goddess of love and beauty. Interestingly, Venus is one of the two planets in our solar system that rotates in a clockwise direction around its axis.

Planet Earth

Planet Earth is positioned as the third celestial body from the Sun and stands out as the largest within the Earth group. The distinct and unparalleled conditions present on Earth have facilitated the development and evolution of life on this planet.

Earth’s atmosphere consists predominantly of nitrogen, making up approximately 78% of its composition, with oxygen following closely at 21%. Additionally, the atmosphere contains a small percentage of carbon dioxide and other gases, collectively constituting 1%. Both oxygen and nitrogen play crucial roles in the construction of DNA. Furthermore, the ozone layer, found within Earth’s atmosphere, serves as a protective barrier, effectively absorbing solar radiation. Plant life on Earth has the remarkable ability to synthesize oxygen through the process of photosynthesis, converting carbon dioxide into this vital gas. The presence of these plants is imperative, as without them, our planet would resemble Venus. On the other side of the spectrum, a certain amount of carbon dioxide in the atmosphere is necessary to maintain Earth’s temperature at a level suitable for sustaining life.

Approximately 70% of Earth’s surface is covered by water. In contrast to the Moon and Mercury, Earth displays a limited number of craters. Scientists hypothesize that these craters have eroded over time due to wind and soil erosion, resulting in their scarcity.

The Moon, which is the Earth’s satellite, has a diameter that is a quarter of the Earth’s diameter, making it comparatively large for a satellite. The gravitational pull of the Moon influences the Earth’s bodies of water, resulting in the occurrence of tides. Notably, the Moon’s rotation on its axis and its orbit around the Earth are synchronized, resulting in the Moon consistently presenting only one side towards the Earth.

Mars

Mars, the fourth planet in our solar system, is approximately half the size of Earth. For a considerable period of time, it was hypothesized that Mars harbored life. People observed formations on its surface that appeared to resemble buildings, roads, and even colossal sculptures. However, these observations were ultimately proven to be optical illusions. Despite numerous research missions, no evidence of life on Mars has been discovered.

The atmosphere of Mars shares a similar composition to Venus, consisting of about 95% carbon dioxide. However, due to its thin and rarefied nature, there is no greenhouse effect, resulting in a maximum surface temperature of around 0°C and atmospheric pressure 160 times lower than that of Earth. While the Martian atmosphere does contain water vapor and polar ice caps, liquid water does not exist on its surface.

Due to its greater distance from the Sun, the length of a year on Mars is nearly double that of Earth. The rate of rotation around its axis is nearly identical to that of Earth, resulting in a day that lasts 24 hours and 40 minutes. Mars has a tilt of 25.2°, allowing for the presence of seasons, similar to Earth.

Mars is accompanied by two satellites, Phobos and Deimos, which are irregularly shaped rocks of relatively small size. The planet was named after the Roman god of war due to its distinct red coloration.

Jupiter

Jupiter, the largest planet among the giants, is located beyond Mars, separated by a belt of asteroids. With a mass twice that of all other planets, moons, comets, and asteroids combined, Jupiter is only surpassed by Venus in terms of brightness in our Earth’s sky. From ancient times, people have observed Jupiter and associated it with the most powerful deities in their respective pantheons. The name Jupiter comes from the Roman god, who was the ruler of all gods.

Jupiter is classified as a gas giant. The planet’s atmosphere is characterized by swirling clouds of sulfur compounds, creating brown and white streaks that move at incredible speeds. One of Jupiter’s most famous features is the “Big Red Spot,” a massive vortex.

Saturn, the sixth planet in our solar system, is located at a considerable distance from the Sun. Its atmosphere is composed mainly of hydrogen (96%) and helium (4%), with small amounts of other gases mixed in. The winds on Saturn are incredibly strong, reaching speeds of up to 1,800 km/h, making them the most powerful in the entire solar system. Within Saturn’s atmosphere, there are also distinctive patterns of clouds, including streaks and patches of giant vortices, although they are not as prominent as those found on Jupiter.

Due to its distance from the Sun, Saturn takes approximately 29.5 Earth years to complete one orbit around it. Interestingly, the tilt of Saturn’s axis is similar to that of Earth’s. Moreover, Saturn is known for its rapid rotation, second only to Jupiter in speed. This is because Saturn’s surface is not solid but fluid, like other gas giants. In fact, Saturn’s density is so low that it is believed to be less dense than water and could theoretically float on its surface.

One of Saturn’s most notable characteristics is its magnificent set of seven rings. Composed of countless icy fragments that reflect light with exceptional clarity, these rings are incredibly prominent. Spanning a distance of 73,000 kilometers and measuring a mere 1 kilometer in thickness, the rings are hypothesized to be remnants of a satellite that was torn apart by the immense gravitational force of the planet.

Uranus

Uranus is the seventh celestial body from our Sun. It has a distinctive blue-green hue due to its atmosphere, which scientists believe is caused by the presence of methane. The cores of Uranus and Neptune are commonly referred to as “ice giants” because they are believed to be primarily composed of ice. With an average surface temperature of -224°C, Uranus holds the title for being the coldest planet in our solar system. The winds on Uranus can reach incredible speeds of up to 900 km/h. It takes approximately three hours for sunlight to travel from the Sun to Uranus, and a single year on this planet is equivalent to 84 Earth years.

Similar to Saturn, Uranus is encompassed by rings. These rings are not as vibrant and are positioned at an approximately 90° angle to the planet’s orbit. Interestingly, Uranus itself rotates “sideways” with an axis tilt of 99°. Consequently, half of the Uranian year experiences daytime in the southern hemisphere and nighttime in the northern hemisphere, while the other half reverses this pattern.

Just like Venus, Uranus also rotates in a clockwise direction on its axis. At present, there are 23 known icy satellites orbiting Uranus.

Data on Neptune was reliably obtained by Voyager 2 back in 1989. Neptune’s upper atmosphere is composed of hydrogen (80%), helium (19%), and methane (1%). It is the high presence of methane that accounts for the planet’s striking blue hue.

Periodically, dark storm spots come and go within Neptune’s atmosphere. It is believed that Neptune has an icy core at its center, while the mantle is made up of a liquid mixture of water and ammonia. The average temperature on the planet’s surface is a chilling -214°C.

It takes nearly 5 hours for sunlight to reach Neptune, and a Neptunian year is equivalent to 165 Earth years. The planet completes a full rotation on its axis quite swiftly, with a day lasting just 17 hours. The tilt of Neptune’s axis is similar to Earth’s, at 28°.

Currently, there is a knowledge about 14 satellites orbiting Neptune, with only one (Triton) possessing a spherical form. Triton is also unique as the largest satellite in the system with a retrograde rotation. In addition, Neptune is surrounded by three rings, although their visibility is quite faint.

Space objects that cannot be classified as dwarf planets, planets, or their satellites are known as small bodies of the solar system. This category includes comets, bolides, meteorites, asteroids, centaurs, damocloids, interplanetary gas, and dust.

Comets

Comets are celestial objects that travel in elongated orbits. They consist of frozen gases and cosmic dust.

The shapes of comet tails are usually indistinct and somewhat see-through. Astronomers have currently documented 6,339 comets that are situated close to planets or within the inner part of the solar system.

Asteroids, which lack atmosphere and have an irregular shape, are smaller celestial bodies that orbit the Sun and are inferior in both size and mass to planets. The majority of asteroids are found in the region between the orbits of Mars and Jupiter, known as the asteroid belt. Notable examples of asteroids include the dwarf planet Ceres, as well as Pallada, Vesta, and Hygeia.

Dwarf planets

A dwarf planet is a celestial body that, although not classified as a satellite, lacks the ability to clear its orbit of other objects. It orbits the Sun and possesses enough mass to maintain a spherical shape. Scientists have identified over 40 celestial bodies that meet the criteria for being classified as dwarf planets. However, only a handful have been officially recognized as such, including Pluto, Haumea, Erida, Makemake, and Ceres.

Interstellar Dust

Interstellar dust refers to cosmic dust particles that have sizes ranging from 2-3 molecules to 0.2 microns. The composition of dust can be categorized into several types, including comet dust, asteroid dust, and dust from the Kuiper belt, which is a region located beyond Neptune’s orbit. Additionally, the comparison of particle characteristics indicates the existence of interstellar dust that traverses through our solar system.

The solar system is a collection of celestial bodies, including the Sun and various other astronomical objects that orbit around it. These bodies consist of planets, moons, asteroids, and other entities. While the solar system is not unique, numerous other planetary systems have been identified thus far. Situated within the Milky Way galaxy, the solar system is positioned in a specific region known as the Orion Arm.

Defining the exact boundaries of our planetary system remains a topic of debate among scientists. Some experts argue that the impact of the solar wind on interstellar space should be considered. Where the solar wind encounters interstellar matter and is halted, a boundary known as the heliopause is formed. This heliopause is located approximately 113 to 120 astronomical units (a.u.) away from the Sun.

Nevertheless, there are astronomers who also differentiate the gravitational boundary of our solar system, known as Hill’s sphere. This region defines the extent of space where the gravitational pull of the Sun is dominant over the gravitational pull of other stars. In the case of our Sun, this sphere has a radius equivalent to approximately one light-year or 63 thousand astronomical units (a.u.).

Formation and makeup

The Sun is the central celestial body within the solar system and constitutes an overwhelming 99.86% of its total mass. Currently, there are eight planets orbiting around this luminous entity. Among these, the closest four planets resemble Earth in terms of their characteristics, while the subsequent four are classified as gas giants. Positioned between these two groups is the main asteroid belt, known for its abundance of asteroids. Additionally, beyond Neptune’s orbit, the outermost gas giant, lies another cluster of asteroids known as the Kuiper belt.

In 2006, a new phrase, dwarf planet, was brought forth. These celestial bodies are akin to typical planets, but they possess the distinctive characteristic of harboring other sizable objects within their orbit. As of 2019, there have been 5 entities bestowed with the classification of dwarf planets, yet experts in astronomy posit that there may exist a substantially larger number.

Within planetary systems, one can also find satellites revolving around the planets. A few of these satellites, such as Ganymede and Titan, are of such considerable dimensions that they surpass the magnitude of Mercury, the smallest of the planets.

The Sun is just one of the numerous stars within the Milky Way galaxy. With a diameter of approximately 1.4 million kilometers, it surpasses the Earth’s diameter by over 100 times. The Sun’s mass is estimated to be between 2 and 10^30 kilograms, an immense value that is 333,000 times greater than the Earth’s mass.

While the surface temperature of the Sun measures 5500°C, there exists a region above the surface known as the corona. Interestingly, the temperature of the corona can soar up to 1.5 million degrees Celsius. The mechanism responsible for this extraordinary heating of the solar corona remains unknown.

At the core of the star, there is a central region with a diameter of 300,000 km. The temperature in this area is estimated to be around 13.5 million degrees, while the pressure reaches an astonishing 200 billion atm. These extreme conditions are crucial for the process of fusion. During fusion, hydrogen atoms combine and transform into helium, releasing a significant amount of heat. This fusion process serves as the primary source of heat for the entire solar system.

Currently, the Sun is composed of 73.4% hydrogen and 24.9% helium. It is evident that as a result of thermonuclear fusion, hydrogen is gradually depleted (over 4 million tons of hydrogen are consumed every second), leading to a decrease in its proportion within the star’s composition over time.

The celestial bodies of the solar system

The ecliptic is the plane in which the Earth’s orbit is located. It is accurate to say that the orbits of all the other planets also lie in this same plane, with a maximum deviation of 7 degrees observed for Mercury. Additionally, all the planets rotate in the same direction, providing indirect evidence that the entire matter of the solar system was once a single entity.

Not only do planets orbit around the star, but they also spin on their own axis. It is commonly accepted that 1 orbit around the star is equivalent to a year on the planet, while one rotation on its own axis is equivalent to a day. As a result, a day on Jupiter lasts approximately 10 hours, and a year on Jupiter is approximately 11.86 Earth years.

The terrestrial planets

The planets belonging to the Earth group share a common characteristic – they possess a solid outer layer that is immediately followed by an atmosphere. These planets are relatively small in size and typically have very few or no natural satellites. Unlike Saturn, they do not possess rings. Composed primarily of solid rock and heavy elements such as oxygen, iron, and silicon, each planet in the Earth group is believed to have a metallic core surrounded by a mantle dominated by silicon. On the surface, however, there exists a relatively thin crust.

Mercury is the planet that is closest to the Sun, and its average distance from the Sun is about 58 million kilometers. Additionally, it is the smallest and fastest planet in our solar system. It takes approximately 87.969 Earth days for Mercury to complete one orbit around the Sun, while a day on Mercury lasts about 58.646 Earth days. Interestingly, for every 2 orbits that Mercury completes around the Sun, it also completes exactly 3 rotations on its own axis. The radius of Mercury is approximately 2439.7 kilometers, and its mass is estimated to be about 0.055 times the mass of the Earth. Unlike some other planets, Mercury does not have any natural satellites orbiting around it.

Venus

Venus is the planet that follows the Sun in our solar system. It is often referred to as the “Earth’s sister” due to its similar size. Venus has a radius of 6050 km, which is 95% of the Earth’s radius. The planet’s mass is 18.5% less than that of Earth. Venus is located at a distance of 107.5 to 108.2 million kilometers from the Sun. Despite being closer to the Sun than Earth, Venus is actually hotter than Mercury. Its average temperature is around 477 degrees Celsius, with minimal fluctuations. This high temperature is attributed to Venus’ dense atmosphere, which is composed of 96% carbon dioxide. The atmospheric density is so extreme that the surface pressure on Venus reaches 93 atm. If Venus had an atmosphere similar to Earth’s, its temperature would not exceed 80 degrees Celsius. Unlike Earth, Venus does not have any natural satellites. However, there is a theory that suggests Mercury may have once had a satellite.

Planet Earth

Planet Earth, the place where humanity originated, is the third planet in our solar system. Its distance from the Sun varies between 147 and 152 million kilometers. The average distance, which is approximately 149.6 million km, is commonly used in astronomy as a unit of measurement known as the astronomical unit (a. e.). With an average radius of 6371 km, Earth is part of the terrestrial group of planets. It has a mass estimated at 5.97-10 24 kg. One distinctive feature of Earth is its large satellite, the Moon, which has a radius of 1737 km.

Mars

Mars is the final planet in our solar system that resembles Earth in many ways. Its distance from the Sun can vary, ranging from 206 to 249 million kilometers. The Red Planet has a smaller mass compared to Earth, being just one-tenth of its size, and its radius measures 3389.5 kilometers. A Martian day lasts for 24 hours and an additional 37 minutes, while a Martian year is equivalent to 687 Earth days. Mars is accompanied by two small satellites, Phobos and Deimos, although they are significantly smaller than our Moon. The largest of the two, Phobos, has an irregular shape and measures 26.8×22.4×18.4 kilometers in size.

The gas giants are the outer planets of our solar system. They are enormous in size compared to Earth and lack a solid surface for potential human landing. The majority of these planets are composed of an atmosphere that transitions into a liquid state due to increased pressure at lower altitudes. There is no distinct boundary between the liquid ocean and the atmosphere, and below the ocean lies a solid core under even higher pressure.

Hydrogen is the primary element found in the giant planets, ranging from 80% in Neptune to 96% in Saturn. Helium is the second most abundant element, while all other elements account for no more than 1-3%.

Each gas giant possesses numerous satellites, some of which are larger than dwarf planets. Additionally, all gas giants have rings surrounding them, with Saturn’s rings being the most prominent.

Jupiter

Jupiter is the gas giant nearest to the sun. It is the second largest object in our solar system, with an estimated average radius of 69,911 kilometers. Its mass is 318 times greater than that of Earth. A year on Jupiter lasts 11.86 Earth years, and it completes a full rotation on its axis in just 10 hours. Jupiter’s orbit has a radius ranging from 740 to 816 million kilometers. As of now, scientists have confirmed the existence of 79 satellites orbiting Jupiter, but the actual number is likely to be over 100. Notable among these satellites are Ganymede, Io, Europa, and Callisto, which were first observed by Galileo in 1610 and were the first satellites of other planets to be discovered by astronomers.

Saturn

Located beyond Jupiter’s orbit, Saturn is a planet with impressive dimensions. It has an estimated radius of 58,232 kilometers and a mass equivalent to 95.2 times that of Earth. The distance between Saturn and the Sun varies throughout its elliptical orbit, with its perihelion being approximately 1.353 billion kilometers away, and its aphelion at a distance of about 1.513 billion kilometers. Unlike Jupiter, which rotates swiftly, a day on Saturn lasts a bit longer, with a duration of 10 hours. As for its orbital period, Saturn takes approximately 29.5 Earth years to complete one revolution around the Sun. As of 2019, scientists have identified a total of 82 satellites orbiting the planet, with the largest one being Titan, which has a radius of 2,576 kilometers. One fascinating aspect of Titan is the presence of lakes and rivers on its surface. However, these bodies of liquid are not filled with water but rather with methane and ethane.

Uranus

Uranus, the following celestial body in our solar system, has a varying distance of 2.75 to 3 billion km from the Sun. With a radius of 25362 km, Uranus possesses a mass that is 14.5 times greater than that of Earth. A single rotation on Uranus takes approximately 17 hours, while a complete orbit around the Sun takes 84 Earth years. As of now, Uranus boasts a total of 27 satellites, the most prominent of which is Titania, measuring 788 km in radius.

Neptune is currently the most distant planet in our solar system. It is situated approximately 1.45-4.52 billion kilometers away from the Sun. The mass of Neptune is 17.1 times greater than that of Earth, and its radius measures 24622 km. A day on Neptune lasts almost 16 hours, while a year is equivalent to 164.79 Earth years. Similar to Uranus, Neptune falls under the category of ice giants, which are a unique class of gas giants. These ice giants, much smaller in size compared to Jupiter and Saturn, consist mainly of ice, methane, ammonia, and hydrogen sulfide. In total, Neptune has 14 moons, with Triton being the largest among them. Triton measures approximately 1,353 kilometers in radius.

The planet number nine

The confirmation of the existence of the Ninth Planet can only be achieved through visual observation, as calculations do not provide any assistance in estimating its location with even a moderate level of accuracy. Currently, only the approximate orbit of this celestial body is known. Given its considerable distance from Earth and its relatively slow speed of movement, detecting the Ninth Planet proves to be an exceedingly challenging task.

There is still no agreement on the exact location of the border between a planet’s atmosphere and interplanetary space (outer space). For Earth, it is widely accepted that this border is either 100 or 122 km.

The Sun releases a continuous stream of particles known as the solar wind. This is what fills the interplanetary space within our solar system. The solar wind consists of electrons, protons, and other ions. This wind actively erodes the atmospheres of Venus and Mars, causing these planets to gradually lose their atmospheric layers. However, Earth’s atmosphere is shielded from the solar wind by a robust magnetic field.

Additional items

All dwarf planets, with the exception of Ceres, can be found within the Kuiper Belt, which is a collection of asteroids that exists beyond the orbit of Neptune. There is also another belt of asteroids known as the main asteroid belt, which is situated between Mars and Jupiter. This is where Ceres is located. The main asteroid belt earned its name because objects within it were discovered much earlier than those in the Kuiper Belt. For instance, Ceres was first observed in 1801, whereas Pluto was not discovered until 1930. However, it is important to note that the total mass of objects within the Kuiper Belt is estimated to be 20-200 times greater than that of the main belt.

Scientists have identified a separate group of asteroids that reside between the orbits of Jupiter and Neptune. These asteroids are referred to as centaurs. The largest known centaur, Chariklo, has a radius of 129 km.

There is a speculation that there might exist another group of celestial objects beyond the Kuiper belt, known as the Oort cloud, located at a distance of 50-100 thousand a.u. The Oort cloud is approximately 1000 times farther than the Kuiper belt. Currently, there have been only 5 discovered bodies that could potentially belong to the Oort cloud.

The creation and development of the solar system

Currently, the dominant theory in science is the nebular hypothesis, which suggests that the solar system was formed from a cloud of gas and dust. This process started approximately 4.57 billion years ago. As a result of gravitational forces, the particles in this cloud were attracted to each other, causing the cloud to gradually shrink in size. Simultaneously, its rotation speed increased, leading to an increase in the density of matter, temperature, and pressure at the center.

After around 50 million years, the hydrogen concentration and temperature at the center of the cloud reached levels that initiated thermonuclear fusion. This is how the Sun came into existence.

The planets that formed in close proximity to the sun were heated by its intense heat, preventing substances like water, ammonia, and methane from solidifying. On the other hand, the giant planets were created further away from the star, where temperatures were so frigid that these substances became solid.

Initially, the Earth was extremely hot and lacked a solid crust. The denser materials sank towards the center of the molten Earth, while the lighter substances rose to the surface. As time passed, the Earth gradually cooled, leading to the formation of a solid crust. Similar processes occurred on other Earth-like planets.

Scientists believe that the Moon formed as a result of a collision between Earth and another planet named Teia. This collision caused some of Earth’s matter to be ejected into space, eventually coalescing to form a satellite orbiting our planet.

Thermonuclear reactions occurring within the Sun are undergoing acceleration, leading to a gradual increase in its luminosity at a rate of approximately 10% per billion years. This ongoing process is predicted to persist for a total duration of 3.5 billion years, ultimately culminating in a remarkable 40% surge in brightness.

Following this phase, the Sun will eventually deplete its hydrogen supply, which is estimated to transpire in approximately 7.7 billion years. At this point, the Sun will undergo a transformation into a red giant, characterized by a significant expansion in size. Consequently, the Sun will engulf both Mercury and Mars, and there is a possibility that Earth will also be consumed in the process. As time progresses, the Sun will then transition into a white dwarf, subsequently evolving into a black dwarf. Concurrently, it will gradually diminish in size and cease emitting heat to its surroundings.

Exploration and investigation

Ancient civilizations such as the Egyptians, Sumerians, Chinese, and Mayans were the first to have knowledge of the solar system. They observed the sky and discovered the existence of the initial six planets. It was evident to them that the Sun revolved around the Earth, leading to the geocentric model of the solar system. According to this model, the Earth was believed to be at the center, while the planet’s trajectories were complex, with some of them even reversing their movements.

In 1781, William Herschel made a significant discovery by finding Uranus, the seventh planet. The year 1801 marked the discovery of the first asteroid, Ceres.

Calculations revealed that Uranus did not adhere to the expected orbit based on Newtonian mechanics. This led to the assumption that there must be another planet beyond Uranus, which was later named Neptune. It was first theorized in 1846 and visually observed by Johann Galle.

Pluto, discovered in 1930, was initially considered the tenth planet. However, further observations revealed that it shared its orbit with other celestial bodies. In 1992, the existence of the Kuiper Belt, which includes Pluto, was proven. In the early 2000s, several celestial bodies within the Kuiper Belt, including Pluto, were classified as dwarf planets in 2006.

The progress of space exploration has played a significant role in studying the solar system. In 1959, the Soviet Luna-1 spacecraft successfully overcame Earth’s gravitational pull and conducted the first-ever survey of the Moon. Following that, spacecraft have been dispatched to all the planets in our solar system, as well as several satellites, asteroids, and comets. “Voyager 1, which was launched in 1977, is presently investigating the heliopause region.”

The Moon remains the only celestial body in the solar system where humans have set foot. A total of six manned missions were carried out on the Earth’s satellite between 1969 and 1972.

Fascinating trivia

An interesting occurrence referred to as the Joshua phenomenon can be witnessed on the planet Mercury. This phenomenon occurs when the planet is near perihelion, causing its rotation around the star to surpass its rotation around its own axis. As a result, observers on the planet will perceive the Sun to move across the sky in the opposite direction. It may even appear to rise and set in different locations. The name of this phenomenon is derived from the biblical story of Joshua, who was said to have halted the movement of the Sun.

In July 1994, astronomers witnessed the historic event of two celestial bodies in our solar system colliding. Jupiter was struck by Shoemaker’s Comet Levi 9, which was comprised of 21 fragments, each approximately 2 kilometers in diameter. This collision emitted an extraordinary amount of energy, estimated to be equivalent to 6 trillion tons of TNT.

Out of the eight planets in our solar system, six of them rotate on their axes in the same direction as they revolve around the Sun. However, Venus and Uranus are the exceptions to this rule. Venus rotates in the opposite direction, while Uranus has its axis almost aligned with the plane of the ecliptic. Consequently, each pole of Uranus is exposed to sunlight for a period of 42 years, followed by 42 years of darkness.

In 1921, the rings of Saturn disappeared abruptly. Concerns arose in the media about the possibility of particles from these rings heading towards Earth. In reality, the rings were simply tilted towards Earth, rendering them invisible.

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List of utilized sources

– https://en.wikipedia.org/wiki/Solar_system

– https://spacegid.com/planets-of-our-solar-system.html#i-8

– https://v-kosmose.com/journey-through-the-solar-system/

– http://solarviews.com/eng/solarsys.htm

– https://www.nationalgeographic.com/science/space/our-solar-system/

A planet is a celestial body that orbits a star and has sufficient mass to achieve hydrostatic equilibrium, where the force of gravity is balanced by the energy produced by its core. This equilibrium allows the planet to maintain a spherical shape and dominate its orbit, preventing other bodies from interfering with its trajectory.

Our planet Earth, along with the other seven planets in the solar system, revolves around the Sun. While they all possess the characteristics that define them as “planets,” they differ from one another based on their composition and location within the solar system.

To learn more about the organization and structure of the Sun, click here.

Characteristics of Planets

The composition of the planets in the solar system determines their categorization, which includes:

Terrestrial planets. These planets, also known as “telluric” planets, are characterized by their high density and are primarily composed of rocky and metallic materials. The following planets in our solar system fall into this category: Mercury, Venus, Earth, and Mars.

Gas giants. Also referred to as Jupiterians, these are large celestial bodies that rotate at a much faster rate than Earth. These planets possess dense atmospheres, strong magnetic fields, and numerous satellites. The gas giants in our solar system are Jupiter, Saturn, Uranus, and Neptune.

Fascinating Facts about Planets! Gas giants have a faster rotation speed compared to Earth.

Planets are also classified based on their position in the solar system. In terms of their distance from the Sun, planets are divided into:

Fascinating facts about planets! The outer planets have a remarkably rapid rotation on their axis. For instance, Jupiter completes one rotation in less than 10 hours, Saturn in under 11 hours, Neptune in just over 16 hours, and Uranus in almost 17 hours and a quarter.

Terrestrial planets. These are the planets located closest to the Sun, within the asteroid belt. They include: Mercury, Venus, Earth, and Mars.

Gas giant planets. These are the planets furthest from the Sun, beyond the asteroid belt. They are: Jupiter, Saturn, Uranus, and Neptune.

Solar System’s Planets

Pluto

Unearthed in 1930, it was considered a planet until 2006. Following a heated international debate, a decision was made to reclassify Pluto as a “dwarf planet” within the Solar System due to its failure to meet the criteria for being classified as a planet. Unlike planets, Pluto does not have orbital dominance, as its orbit is not clear of other celestial bodies and it possesses five satellites with similar orbits. Pluto is categorized as a rocky outer-type dwarf planet due to its position as the furthest celestial body from the Sun. In addition to Pluto, other dwarf planets have been discovered, including Ceres, Haumea, Makemake, and Eris.

Pluto, the outermost planet in our solar system, holds the title for being the most distant from the Sun. Its extreme distance is so vast that if one were to stand on Pluto’s surface, the Sun would appear merely as a brilliant star in the sky.

With a diameter measuring 2,300 kilometers, Pluto is only half the size of Mercury, the planet that follows it in terms of size. In fact, Pluto is even smaller than some satellites, such as Io, a moon of Jupiter, which boasts a diameter of 3,600 kilometers, or our very own Moon, whose diameter measures 3,470 kilometers.

While most planets adhere to a predictable elliptical orbit in the same plane, Pluto defies convention and follows a highly complex orbit that is distorted to the point of occasionally crossing Neptune’s orbit in a different plane. At certain junctures, Pluto can even appear closer to the Sun than Neptune, only to move away once again.

Planet Earth

The planet with the highest density in our solar system and the unique presence of water on its surface is Earth. Ranking as the fourth largest planet, it follows Venus and is accompanied by its only natural satellite, the Moon. Earth is the place we call home, and its surface is predominantly covered with vast oceans, giving it a blue appearance when observed from space. This planet stands alone as the only one where water exists in a liquid state.

Additionally, water can be found in the form of small crystals within the clouds of Earth’s atmosphere, contributing to its distinctive white color, combined with hints of blue. Comprised mainly of nitrogen and oxygen, Earth’s atmosphere possesses yet another distinguishing characteristic.

Earth’s atmosphere contains relatively little CO2 compared to Venus and Mars. Initially, this CO2 was dissolved in seawater and consumed by the earliest life forms on Earth. These organisms were small green algae that, as they grew and multiplied, released oxygen into the atmosphere through their metabolic processes.

Geologically, Earth is an extremely active planet. Its crust is composed of large tectonic plates that are constantly shifting due to underground forces. Europe, Africa, and the Americas were once part of a single plate that gradually separated over time. Even today, these plates continue to move apart by a few centimeters each year (according to the Geologic Time Scale).

At the thinnest parts of the Earth’s crust, new crust is constantly being formed beneath the ocean. As a result, these tectonic plates collide in certain regions, causing frequent earthquakes.

If you want to learn more about the Earth’s structure, you can find more information here.

Discover Mercury

The smallest planet in our solar system, Mercury, has a rocky body that is similar to Earth. What sets it apart is its core, which takes up nearly half of the planet’s volume and generates a strong magnetic field. Unlike other planets, Mercury has no natural satellites. You can catch a glimpse of Mercury within two hours after sunset or before sunrise.

One of the unique characteristics of Mercury is its tilted ecliptic plane, which is more pronounced compared to other planets. Additionally, when Mercury reaches its closest point to the Sun, known as “perihelion,” it is less than two-thirds of its distance from the Sun at its farthest point, called “aphelion.”

Due to its proximity to the Sun, Mercury receives six times more solar radiation than Earth. As a result, the temperature on its sunlit side is incredibly high.

Similar to the Moon, the planet’s surface is covered in craters, which were created by meteorites of various sizes. These craters are a common feature during the early stages of the solar system’s formation.

Due to the absence of erosion caused by the lack of atmosphere, these craters have remained intact, much like on the Moon. It is probable that the planet has never had an atmosphere, as its small size and low gravity would not allow for the retention of a gaseous atmosphere.