The Solar System
1. The Solar System consists of the Sun and objects that orbit it, formed around 4.6 billion years ago.
2. The Sun, a G-type main-sequence star, is the most massive object, containing over 99.86% of the system’s mass.
3. The eight planets Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune are divided into terrestrial and giant planets, with the giants mainly made of gases and liquids.
4. There are also at least nine known dwarf planets, including Pluto and Eris, and many smaller bodies like asteroids and comets.
5. The Solar System is surrounded by the heliosphere, influenced by the Sun’s solar wind, which ends at the heliopause around 75–90 AU. The outermost region, the Oort cloud, extends to 200,000 AU and is believed to be the source of long-period comets.
6. Proxima Centauri, the closest star, is 4.25 light-years away.
Sun:
1. The Sun is a star located at the center of the solar system.
2. Its mass (332,900 Earth masses) makes up 99.86% of the total mass of the solar system.
3. It releases enormous amounts of energy by fusing hydrogen atoms in its core. This energy is primarily emitted into space in the form of electromagnetic radiation.
4. The Sun is a G-type main-sequence star. With an apparent magnitude of +4.83, the Sun is much brighter than about 85% of the stars in the Milky Way, most of which are red dwarfs.
5. The Sun belongs to a class of stars known as metal-rich stars.
Mercury:
1. Mercury is the planet closest to the Sun and the smallest in the solar system. It takes 88 days to complete one orbit around the Sun. Due to the intense brightness of the Sun, it is rare to observe Mercury.
2. Its surface experiences extreme temperature variations, with 700 K during the day and −100 K at night. Its axial tilt is very small, but its orbital eccentricity is high.
3. Uniquely, as Mercury completes three rotations on its axis for every two orbits around the Sun.
4. Mercury’s surface features large craters, and its interior contains a large iron core, which generates a magnetic field. In 1974–75, the Mariner 10 spacecraft flew close to Mercury and mapped it.
5. Later, in 2008, the Messenger spacecraft captured more images, and in 2011, it was inserted into orbit around Mercury.
Venus:
1. Venus is the second planet in the solar system. It has a very hot atmosphere and has similar density and gravitational pull to Earth.
2. Venus appears as the second brightest object in the night sky after the Moon. It is referred to as the “morning star” in the morning and the “evening star” in the evening.
3. Venus’s atmosphere consists of 96% carbon dioxide, and its surface temperature is 737 K (464 °C). Conditions on Venus make it impossible for life to exist.
4. Venus orbits the Sun in 224.7 Earth days, and it is a planet with similar size to Earth.
5. However, it differs from Earth in several ways. In September 2020, phosphine was discovered in Venus’s atmosphere, which suggests the potential for organic life.
Earth:
1. The Earth is the third planet from the Sun in the solar system.
2. It is notable for having an environment suitable for the advancement of life and providing the conditions necessary to sustain life.
3. Earth is believed to have formed about 4.54 billion years ago. Approximately 71% of its surface is covered by water, mainly in the form of oceans, landmasses, and islands.
4. Earth orbits the Sun once every 366.26 days and rotates on its axis, which is tilted at an angle of 23.4°, causing seasonal variations and climatic patterns.
5. This tilt results in temperature changes and weather phenomena.
6. The mineral resources of Earth and the products formed in its biosphere have supported the growth of the human population.
7. Various aspects of Earth and its natural features have created a habitat where humans and other life forms can coexist.
8. This has led to the formation of different cultures and beliefs around the world.
Mars:
1. Mars is a planet in the solar system. It is the fourth planet from the Sun.
2. In the solar system, it is the second smallest planet after Mercury. The ancient Romans named this planet after the god of war.
3. The iron oxide present on its surface gives the planet its reddish appearance, which is why it is called Mars. Its surface contains features similar to those on Earth, such as craters like those on the Moon, volcanoes, valleys, deserts, and polar ice caps. Mars has a rotation period and seasonal changes similar to Earth.
4. The highest volcano in the solar system, Olympus Mons, and one of the largest vertical canyons, Valles Marinera’s, are both located on Mars.
5. Until 1965, when Mariner 4 successfully flew close to Mars, it was believed that liquid water might exist on the surface of the planet.
6. The dark and light patches near the poles were thought to be oceans and continents. Long, dark grooves on the surface were also believed to be irrigation channels.
7. Later, this was explained as an optical illusion. However, evidence collected by unmanned missions indicates that Mars once had significant amounts of water.
8. Mars has two moons, Phobos and Deimos. These moons are small and irregularly shaped.
9. They are likely captured asteroids, much like the small asteroid 5261 Eureka, which is part of Mars’ Trojan asteroids, pulled into orbit by Mars’ gravity.
Jupiter:
1. Jupiter is the fifth and largest planet in the solar system, with a mass over two and a half times that of all other planets combined.
2. It is a gas giant primarily composed of hydrogen and helium, with a rocky core.
3. Jupiter has 79 moons, including Ganymede, the largest moon in the solar system.
4. It rotates quickly, completing one turn in about 9 hours and 50 minutes, and orbits the Sun once every 12 Earth years.
5. Its atmosphere contains violent storms, including the Great Red Spot.
6. Jupiter was first studied by Galileo in 1610 and has since been explored by missions like Voyager and New Horizons.
7. Future missions may study its moon Europa, believed to have an ocean beneath its icy surface.
Saturn:
1. Saturn is the sixth planet in the Solar System, located 1.4 billion kilometres (869 million miles) from the Sun.
2. It takes about 29.5 Earth years to complete one orbit around the Sun.
3. Saturn is the second-largest planet after Jupiter and is primarily composed of hydrogen and helium, with traces of other elements.
4. It has a diameter nine times that of Earth, yet is 95 times more massive.
5. Saturn’s atmosphere gives it a yellowish appearance due to ammonia crystals, and it has a strong magnetic field, 580 times more powerful than Earth’s.
6. Its rings are made of ice, rock, and dust particles. Saturn has 61 known moons, with Titan being the largest, even bigger than Mercury.
7. Saturn’s winds can reach speeds of up to 1800 km/h. The planet was named after the Roman god Saturn, and its symbol resembles a sickle.
Uranus:
1. Uranus is the seventh planet from the Sun in our solar system and the third largest by diameter.
2. Named after the Greek god Uranus, it appears as a faint object and was not considered a planet by ancient observers due to its slow orbit and dim appearance.
3. Uranus is a gas giant with an atmosphere containing hydrogen, helium, and methane.
4. Its temperature is around -197°C. It has 11 major rings and takes 84 Earth years to orbit the Sun.
5. A day on Uranus lasts 17 hours and 14 minutes, meaning its year equals 43,000 Earth days.
Neptune:
1. Neptune is the eighth and farthest planet in the solar system.
2. The meaning of Neptune refers to the Roman god of the seas. Based on volume, it is the fourth-largest planet in the solar system, and based on mass, it is the third-largest.
3. Neptune has 17 times the mass of Earth and is slightly larger than Uranus, which is 15 times the size of Earth (but with a lower density).
4. On average, Neptune orbits the Sun at a distance of 30.1 AU.
5. Neptune is a gas giant and is located beyond the asteroid belt in the solar system. It has a ring made of gas surrounding it. c