Planets in Solar System
Planets in solar system consist of eight primary planets that orbit the Sun. These planets include Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune.
All Planets in the solar system have its unique characteristics, sizes, and orbits, contributing to the diverse nature of our cosmic neighborhood. Studying these planets provides valuable insights into the formation and evolution of celestial bodies in the universe.
Celestial bodies that follow elliptical orbits around a star are termed “planets.”
- Classification: In our solar system, these planets can be classified into two distinct groups based on their characteristics and positions.
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Type of Planets in solar System
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Description
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Terrestrial
Planets
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- They are also known as Inner planets.
- These planets lie between the Sun and the asteroid belt.
- They are generally made up of rocks and metal and have relatively high densities.
- These include – Mercury, Venus, Earth and Mars.
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Jovian
Planets
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- Jovian planets are also known as Outer planets or Gas Giant planets.
- These planets lie beyond the asteroid belt.
- They are larger than terrestrial planets and have a thick atmosphere consisting of hydrogen and helium.
- They have numerous satellites of their own, for instance, Jupiter and Saturn have 79 and 82 moons respectively (as of 2019).
- All Jovian planets have rings.
- For example, Jupiter has 1 ring, Saturn has 7 rings, Uranus has 13 rings and Neptune has 6 rings.
- Jovian planets include – Jupiter, Saturn, Uranus and Neptune.
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The Differences between the Terrestrial and Jovian planets
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- Distance with respect to the Sun: The terrestrial planets were formed in close vicinity of the Sun as compared to the Jovian planets.
- Thus, it was too warm for gasses to condense to solid particles.
- Effect of solar winds: The solar winds were most intense nearer the sun, it blew away lots of dust and gasses from the terrestrial planets.
- Whereas, the solar winds were not that intense to remove gasses from the Jovian planets.
- Gravity: Terrestrial planets are small compared to the Jovian, their lower density could not back the escaping gasses.
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- Classification Criteria for Planets in Solar System: The International Astronomical Union (IAU) categories include characteristics such as their size, location, and composition.
- Also being in orbit around the Sun, having sufficient mass for self-gravity to form a nearly round shape.
- In 2006, the International Astronomical Union (IAU) introduced the term “dwarf planet” to classify celestial objects that share some characteristics with planets but do not meet all the criteria for a full-fledged planet.
- Pluto is one such object that was reclassified as a dwarf planet.
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International Astronomical Union
- It was founded in 1919, headquartered in Paris, France.
- Its mission is to promote and safeguard the science of astronomy in all its aspects, including research, communication, education and development, through international cooperation.
- It is the global authority for naming planetary features in the solar system.
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Comparative Overview of Terrestrial Planets in Solar System
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Parameter
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Mercury
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Venus
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Earth
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Mars
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Distance from Sun
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Closest planet to Sun
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Average distance
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Average distance
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Average distance of about 227.9 million kilometers
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Atmospheric Composition
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Weak atmosphere
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Rich in CO2 and sulphuric acid clouds
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Rich in N2 and O2
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Rich in CO2 and N2
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Magnetic Field
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No magnetic field
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No magnetic field
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Yes
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A Very weak magnetic field
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Appearance from Earth
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No moon and no ring
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Appears bright due to high albedo
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Appears blue due to abundant water
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The “Red Planet” due to its reddish appearance
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Rotation Direction
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West to East
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East to West
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West to East
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West to East
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Rotation Period (days)
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58.6
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243
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1
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1.025 days
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Revolution Period (days)
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88
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224.7
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365
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687 days
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Shape
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Spherical-harmonic shape
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Oblate spheroid (flattened at poles,bulging at equator)
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Geoid (flattened at poles,bulging at equator)
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Spherical
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Number of Moons
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No
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No
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1(Moon)
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Two small moons, Phobos and Deimos.
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Average Temperature
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–
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Very hot
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Around 14 Degrees
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Around -80 degrees Fahrenheit (-62 degrees Celsius).
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Speed of Rotation (Poleward)
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–
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Decreases poleward
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Decreases poleward
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Near its poles is slower
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The Goldilocks Zone: The Habitable Region for Life in the Universe
- It is a habitable zone around the star, within which the planet supports the conditions for habitat. In this zone, water can exist in liquid form.
Moon: Exploring Earth’s Mysterious Satellite and Its Origins
- About: The Moon, Earth’s natural satellite, is a celestial body that orbits our planet.
- It is the brightest and most prominent object in Earth’s night sky.
- It has no atmosphere of its own.
- Distance from Earth
- The moon is approximately 384,400 kilometers away from the Earth.
- Orbital Period
- It revolves around the Earth in about 27 days.
- Tidal Locking
- Due to tidal locking, only one side of the moon is visible from Earth.
- Tidal locking means the Moon rotates about its axis in about the same time it takes to orbit Earth.
- Apogee and Perigee
- The moon’s distance from Earth varies during its orbit.
- Apogee is the greatest distance between the Earth and the moon.
- Perigee is the nearest point at which the moon revolves around the Earth.
- Origin of the Moon: Exploring Formation Theories and Their Implications
- Giant Impact Theory (Big Splat Theory): The moon’s formation is believed to result from a giant impact shortly after the Earth’s formation around 4.4 billion years ago.
- An object, three times the size of Mars, collided with Earth, causing a significant part of Earth to be blasted into space, eventually forming the moon.
- Fission Hypothesis: Another theory suggests that the moon separated from Earth early in the history of the solar system.
- The Pacific Ocean basin is considered the possible site from which the moon originated.
Note:
- Tidal lock is the situation when an object’s orbital period matches its rotational period. The moon has the same rotation and revolution time period of about 27 days.
- Thus due to the tidal lock effect only one face of the moon is visible from the surface.
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Exploring the Cosmic Divisions: Asteroid belt between Mars and Jupiter
- Asteroid belt is a torus shaped circumstellar disc located roughly between the orbits of Mars and Jupiter.
- It consists of numerous irregular shaped bodies known as asteroids, and also differentiates asteroids from other asteroid populations in the Solar system.
- Planets are differentiated into two groups based on their position with respect to the Asteroid belt and the nature of planets.
- The zone beyond Neptune, from 33-50 AU, is known as the Kuiper Belt. The celestial objects in this zone are known as Trans Neptunian Objects (TNO) or Kuiper Belt Objects (KBO).
- The zone beyond Kuiper Belt is termed as Termination Shock, followed by Heliopause till 100AU.
- Heliopause is a zone which lies outside the physical influence of the Sun.
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