Planets in Solar System: A Brief Introduction
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.
About Planets in solar system:
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.
| Type of Planets in solar System | Description |
|
Terrestrial
Planets |
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Jovian Planets |
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| The Differences between the Terrestrial and Jovian planets |
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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.
International Astronomical Union
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Comparative Overview of Terrestrial Planets in Solar System
| Parameter | Mercury | Venus | Earth | Mars |
| Distance from Sun | Closest planet to Sun | Average distance | Average distance | Average distance of about 227.9 million kilometers |
| Atmospheric Composition | Weak atmosphere | Rich in CO2 and sulphuric acid clouds | Rich in N2 and O2 | Rich in CO2 and N2 |
| Magnetic Field | No magnetic field | No magnetic field | Yes | A Very weak magnetic field |
| Appearance from Earth | No moon and no ring | Appears bright due to high albedo | Appears blue due to abundant water | The “Red Planet” due to its reddish appearance |
| Rotation Direction | West to East | East to West | West to East | West to East |
| Rotation Period (days) | 58.6 | 243 | 1 | 1.025 days |
| Revolution Period (days) | 88 | 224.7 | 365 | 687 days |
| Shape | Spherical-harmonic shape | Oblate spheroid (flattened at poles,bulging at equator) | Geoid (flattened at poles,bulging at equator) | Spherical |
| Number of Moons | No | No | 1(Moon) | Two small moons, Phobos and Deimos. |
| Average Temperature | – | Very hot | Around 14 Degrees | Around -80 degrees Fahrenheit (-62 degrees Celsius). |
| Speed of Rotation (Poleward) | – | Decreases poleward | Decreases poleward | Near its poles is slower |
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.
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- 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.
Exploring the Cosmic Divisions: Asteroid belt between Mars and Jupiter
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Previous Year Question (Prelims)
Match List-I with List-II and select the correct answer by using the codes given below the lists: (UPSC CSE 1998)
| List-I
(Special characteristic) |
List-II
(Planet) |
| A. Smallest planet | 1. Earth |
| B. Largest planet in the solar system | 2. Venus |
| C. Planet second from the sun in the solar system | 3. Jupiter |
| D. Planet nearest to the Sun in the solar system | 4. Mercury |
Codes:
- A-2; B-3; C-5; D-1
- A-3; B-5; C-1; D-2
- A-4; B-1; C-2; D-3
- A-4; B-3; C-2; D-1
Ans: d
Which one of the following statements is correct with reference to our solar system?(UPSC CSE 2002)
- The earth is the densest of all the planets in our solar system
- The predominant element in the composition of earth is silicon
- The sun contains 75 percent of the mass of the solar system
- The diameter of the sun is 190 times that of the earth
Ans: c
Q. The term ‘Goldilock zone’ is often seen in the news in the context of: (2015)
- The limits of habitable zones above the surface of the Earth.
- Regions inside the Earth where shale gas is available.
- Search for Earth like planets in outer space.
- Search for meteorites containing precious metals.
Ans: c
