Solar System and Explorations Lecture 2 PDF

# SOLAR SYSTEM AND EXPLORATIONS ## Lecture 2 ### Solar System The Solar system consists of: 1. The Sun: the central star 2. Eight planets 3. Several dwarf planets 4. Tens of moons or satellites 5. Millions of asteroids 6. Trans-Neptunian Objects (TNOs) 7. Myriads of comets 8. Meteoroids ### SOLA...

# SOLAR SYSTEM AND EXPLORATIONS ## Lecture 2 ### Solar System The Solar system consists of: 1. The Sun: the central star 2. Eight planets 3. Several dwarf planets 4. Tens of moons or satellites 5. Millions of asteroids 6. Trans-Neptunian Objects (TNOs) 7. Myriads of comets 8. Meteoroids ### SOLAR SYSTEM - **Stars:** huge celestial bodies made up of hydrogen and helium that can emit their light and energy from nuclear fusion reactions. - **Planets:** celestial bodies that orbit around the Sun. They don't have the ability to emit light and energy from nuclear fusion reactions. - **Moons:** celestial bodies that orbit around a planet. They don't have the ability to emit light and energy from nuclear fusion reactions. - **Dwarf Planets:** Smaller in size than planets, may also have their moons. - **Asteroid (كويكب):** Smaller than dwarf planets, they are rocky celestial bodies that orbit the sun. - **Comet (مذنب):** An object made mostly of ice and dust, often with a tail, that sometimes orbits the sun. - **Meteoroid (نيزك):** a small piece of an asteroid or comet, it is called meteor when burns up upon entering Earth's atmosphere, creating a streak of light in the sky. - **Galaxy:** A massive system of stars, gas, dust, and dark matter bound together by gravity, such as the Milky Way. - **Nebula:** A large cloud of gas (mainly hydrogen and helium) and dust in space, often a star-forming region or the remnants of an exploded star. Such as Orion Nebula. ### Features of the Solar System * Gravitation controls the motion of the solar system bodies. * The planets from Mercury to Saturn are bright and well visible with a naked eye. * The planets from Mercury to Mars are called inner planets (smaller in size). * The planets from Jupitar to Neptune are called outer planets (larger in size). * Inner and outer planets are separated by asteroids belt * Trans-Neptunian belt (Kuiper belt) is existed after Neptune planet * The planets from outside our solar system are called exoplanets. ### ASTRONOMICAL UNITS (AU) * Distances in the solar system are often measured in astronomical units (AU), which is the mean distance of the Sun and Earth. * 1 AU = 149,600,000 km * The semimajor axis of the orbit of Mercury is 0.39 AU, * The distance of Neptune is 30 AU. * Beyond the orbit of Neptune, there is a huge population of small icy bodies extending out to tens of thousands AUs. * The Solar System has no obvious outer edge. * The distance to the nearest star, Proxima Centauri, is over 270,000 AU. | Planet | Distance to sun (AU) | | :------- | :-------------------- | | Mercury | 0.39 | | Venus | 0.72 | | Earth | 1 | | Mars | 1.52 | | Jupiter | 5.2 | | Saturn | 9.54 | | Uranus | 19.2 | | Neptune | 30 | ### ATMOSPHERIC COMPOSITION OF THE PLANETS | Planet | Composition | | :-------- | :--------------------------------------------------------------- | | Mercury | Oxygen (42%) : Sodium (29%): Hydrogen (22%): Helium (6%) | | Venus | Carbon Dioxide (96.5%) : Nitrogen (3.5%) | | Earth | Nitrogen (78.084%): Oxygen (20.946%) | | Mars | Carbon Dioxide (95.32%): Nitrogen (2.7%): Argon (1.6%) | | Jupiter | Molecular Hydrogen (89.8%): Helium (10.2%) | | Saturn | Molecular Hydrogen (96.3%): Helium (3.25%) | | Uranus | Molecular Hydrogen (82.5%) : Helium (15.2%) | | Neptune | Molecular Hydrogen (80.0%) : Helium (19%) | ### THE SUN * The sun heats the solar system and is at the center of our solar system. It's so massive that it holds 99.9% of the total mass of the solar system. * The sun is 72% hydrogen, 26% helium, and 2% other gases. * By fusing hydrogen with helium, the sun releases large amounts of energy toward Earth. * **Surface Temperature:** 5,500°C * **Mass:** 199 x 1030 kg (333,060 Earths) * **Diameter:** 1,392,684 km * Our sun is a main sequence star with a life expectancy of about 10 billion years. Currently, we're into year 5 billion years of our Sun's lifespan. ### MERCURY * Mercury is closest to the sun, and it is mostly iron. * Low gravity and high temperature, are the reasons for its lack of atmosphere. * Mercury has a comet-like tail that extends as far as 2.5 million kilometers long. Scientists have figured out that it's sodium sputtering from its surface. * Very slow rotation around its axis (One day or one rotation around its axis = 59 Earth days). * Swift Planet, one year or one rotation around the sun = 88 Earth days * **Surface Temperature:** -180 to 430°C * **Distance to Sun:** 57,910,000 km (0.39 AU) * **Moons:** 0 * **Radius:** 2,440 km (the smallest planet in the solar system). * **Orbit eccentricity:** 0.21 ### Exploration missions: * **Mariner 10 (1973-USA):** first spacecraft to fly by the planet. * **MESSENGER (2004-USA):** orbit the planet from 2011 to 2015. * **BepiColombo (2018-ESA/Japan):** to orbit Mercury in 2025. ### VENUS * Venus is the planet next to Mercury; it is the brightest planet. * Astronomers call the Planet Venus "Earth's twin" because it is similar in size, gravity, and material on the surface. * Covered by clouds haze-like layers, atmospheric pressure is intense (thick atmosphere) and it rains sulfuric acid. * About 1% of the incident light reaches the surface of Venus. * **Surface Temperature:** 460°C * **Distance to Sun:** 108,200,000 km (0.72 AU) * **Moons:** 0 * **Radius:** 6,052 km * **Orbit eccentricity:** 0.007 ### Exploration missions: * **Mariner 2 (1962-USA):** first spacecraft to fly by the planet. * **Venera 4 (1967-USSR):** sent the first data from below the clouds, and the first clear pictures of the surface were sent by Venera 14 in 1982. * **Venera 7 (1970-USSR):** was the first spacecraft to land on Venus. * **Venus 1 (1978-USA):** was the first spacecraft to orbit Venus and got the first radar map in 1980. * The most complete maps (about 98% of the planet's surface) were made using the SAR observations of the **Magellan (1989-USA)** spacecraft in 1990-1994. * **Akatsuki (2010-Japan):** is currently orbiting Venus for exploration. ### EARTH * Has moderate temperature from the sun, and the only planet where life is known to exist, yet. * The Earth's main atmospheric constituents are nitrogen (77% by volume) and oxygen (21%). Other gases, such as argon, carbon dioxide, and water vapor are present in minor amounts. * Most of the climatic phenomena occur in the troposphere (lower part of the atmosphere), which reaches up to 8-12 km. * **Surface Temperature:** -88 to 58°C * **Distance to Sun:** 149,600,000 km (1 AU) * **Moons:** 1 * **Radius:** 6,371 km * **Orbit eccentricity:** 0.017 ### MARS * Mars is the red planet next to Earth. It's been one of the greatest frontiers for discovery. * Mars has Earth-like environments like dust storms, deserts, sand dunes, and ice caps. But much of planet Mars is blanketed by red dust. * Similar to Earth, Mars has a summer, spring, autumn, and winter. * The most exciting fact about Mars is that it may have liquid water. At its south pole, a permanently ice-filled crater is the greatest evidence that liquid water lies beneath the planet. * The atmosphere of Mars is very dry, and mainly composed of carbon dioxide (95%). It contains only 2% nitrogen and 0.1-0.4% oxygen. * **Surface Temperature:** -125 to 20°C * **Distance to Sun:** 227,900,000 km (1.52 AU) * **Moons:** 2 * **Radius:** 3,390 km ### Exploration missions: * **Mariner 4 (1964-USA):** first spacecraft to fly by the planet * **Mariner 9 (1971-USA):** first spacecraft to orbit Mars. * **Viking 1 (1975-USA):** was the first spacecraft to land on Mars in 1976. * **Sojourner (1996-USA):** was the first Rover that walked on Mars in 1997 (carried by Pathfinder lander). * **Ingenuity (2020-USA):** First aerodynamic (helicopter) flight on Mars in 2021. * **Mars 2 (1971, USSR), Rosetta (2004, ESA), Mars Orbiter Mission (2013, India), Hope (2020-UAE), Tianwen-1 (2020, China)** are other examples of Mars exploration spacecrafts from other countries. ### ASTEROIDS **Asteroids:** minor bodies that circle the Sun mainly between the orbits of Mars and Jupiter, are often more tilted than the planes of the planetary orbits. ### JUPITER * The largest planet in our solar system. And has the highest atmospheric pressure. * Because of its size, it's contending with the sun in the effective gravity that puts Mercury, Venus, Mars, Earth and the asteroid belt balanced in the middle. * Four of Jupiter's large moons are **Ganymede**, **Callisto**, **lo, and Europa (Galilean moons)**. * Jupiter has a permanent cyclone that's been there ever since it observed. * The rotation of Jupiter is rapid; one revolution takes 9h 55min 29.7s. * There is possibly an iron-nickel core in the center of Jupiter. The core is surrounded by a layer of metallic liquid hydrogen, * **Surface Temperature:** -145°C * **Distance to Sun:** 778,500,000 km (5.2 AU) * **Moons:** 95 * **Radius:** 69,911 km ### Exploration missions: * **Pioneer 10 (1972-USA):** first spacecraft to fly by the planet in 1973. * **Galileo (1995-USA):** first spacecraft to orbit the planet. * **Cassini (1997-USA/ESA/Italy):** took the highest-resolution images ever taken of the planet in 2000 and gave more details about Jupiter atmosphere. * **Juno (2011-USA):** orbits Jupiter from 2016 till now. ### SATURN * It is the second-largest planet, and the lightest planet in the solar system. * The most prominent feature of Saturn is its iconic rings. It's rings are made of liquid ice which formed from remnants of comets, asteroids, and other space debris. * There are 146 moons that orbit the Planet Saturn, such as Titan. * Saturn's atmosphere is filled with methane and ammonia. The ammonia crystals on Saturn swirl around the planet coloring it with a gold tint. * **Titan:** The atmosphere is mainly nitrogen (98.4%) and methane. * **Surface Temperature:** -178°C * **Distance to Sun:** 1,434,000,000 km (9.54 AU) * **Moons:** 146 * **Radius:** 58,232 km ### Exploration missions: * **Pioneer 11 (1973-USA):** first spacecraft to fly by the planet in 1979. * **Cassini (1997-USA/ESA/Italy):** first spacecraft to orbit the planet in 2004, * **Huygens (1997-USA/ESA/Italy):** landed on its moon (Titan) in 2005. ### URANUS * Uranus is the coldest in the solar system, and has 9 bright rings * Uranus has a bluish glow because of methane gas in its atmosphere. Methane gas is known to absorb red light and strongly reflect blue. * Uranus has 27 moons. 5 major moons include Umbriel, Miranda, Ariel, Titania, and Oberon * **Surface Temperature:** -224°C * **Distance to Sun:** 2,871,000,000 km (19.2 AU) * **Moons:** 28 * **Radius:** 25,362 km ### Exploration missions: * **Voyager 2 (1977-USA):** the only spacecraft to fly by the planet in 1989. ### NEPTUNE * The farthest planet from the sun. This is about 30 AU away from Earth. * Neptune has seasons like Earth. Further to this, planet Neptune has the strongest winds of all other planets. * Neptune resembles Uranus with a similar size, composition, and temperature. * Pluto is part of Neptune's orbit. * **Surface Temperature:** -231°C * **Distance to Sun:** 4,498,000,000 km (30 AU) * **Moons:** 16 * **Radius:** 1,737 km ### Exploration missions: * **Voyager 2 (1977-USA):** the only spacecraft to fly by the planet in 1989. ### DWARF PLANETS Smaller in size than planets, may also have their moons | Dwarf Planet | AU | |:-------------|:----:| | Pluto | 39.5| | Eris | 67.7| | Haumea | 43.3| | Makemake | 45.8| | Ceres | 2.77| ### FARTHEST SPACECRAFT A diagram showing the trajectory of the Voyager 1 spacecraft - the farthest spacecraft from Earth - from the Sun to the Alpha Centauri location. ### Kuiper Belt **Kuiper Belt:** is a circular-shaped region of millions of icy bodies extending far beyond the orbit of Neptune that were left over from the formation of our solar system. Scientists call these worlds Kuiper Belt objects (KBOs), or trans-Neptunian objects (TNOs). ### Oort Cloud **Oort Cloud** is a giant spherical shell surrounding the solar system, made of icy, comet-like objects. The distance range from the sun is from 2,000 to 200,000 AU (0.03 to 3.2 light-years)