SOLAR SYSTEM

The solar system consists of the Sun, which is its central star, and the various celestial bodies that orbit around it, including eight planets, their moons, dwarf planets, asteroids, comets, and meteoroids. The Sun provides the necessary gravitational force to hold these objects in orbit. The solar system is divided into two regions: the inner solar system, containing the terrestrial planets (Mercury, Venus, Earth, and Mars), and the outer solar system, dominated by the gas and ice giants (Jupiter, Saturn, Uranus, and Neptune). Beyond Neptune lies the Kuiper Belt, home to dwarf planets like Pluto, and the Oort Cloud, which is the outermost region. The solar system formed about 4.6 billion years ago from a rotating cloud of gas and dust, and it continues to be a dynamic and diverse system that has fascinated scientists and astronomers for centuries.

The Sun:

The Sun is the Solar System’s star. The part of the sun which can be seen normally is known as Photosphere, the outer most part of the sun which is visible only at the time of a solar eclipse is known as corona,

• The Sun contains more than 99.8% of the total mass in the solar system.
• The Sun is primarily made up of hydrogen (H) (70%) helium (He) (28%) together with a small amount of carbon, oxygen, iron, neon and other elements.
• The core of the Sun covers approximately the inner 25% of its radius. At the centre of the core the sun density is more than 150 times that of the water.
• The Sun’s power is produced by the nuclear fusion reaction. Each second more than 70 million tons of hydrogen undergo this process and produce energy in the form of Gamma Radiations.
• The surface of the Sun is called photosphere (5800 k).
• A solar flare is a sudden burst of brightness observed on the Sun’s surface or along its edge, signifying a massive energy release of up to 6 × 10²⁵ joules. Solar flares are thought to occur when magnetic fields, generated deep within the Sun, become twisted and then snap apart.

Sunspots

• Sunspots are short-lived phenomena on the Sun’s photosphere that appear as dark spots in contrast to the brighter surrounding areas.
• They are caused by intense magnetic activity the spots are relatively colder regions of the sun which temperature is about 1500 degree centigrade Sun spots produce strong magnetic radiation which hamper the wireless communication system on earth, the appearing and disappearing of the sun spots in every 11year is called Sun Spot Cycle.

Sun missions

• Japan’s Uchinoura Space Centre launched Solar-B mission to understand the solar flares and coronal mass ejections, which can cause communications blackouts on Earth.
• NASA successfully launched the Solar Dynamics Observatory (SDO), a scientific satellite built to observe and monitor the Sun’s activity.
• India’s ISRO has planned Aditya-1 to be launched to study sun.

Planets

A planet is a celestial body that orbits a star or stellar remnant, is sufficiently massive for its gravity to shape it into a round form, but not massive enough to initiate thermonuclear fusion. It receives light and heat from the Sun.All the planets revolve around the sun from west to east. But Venus and Uranus are the exceptions, which revolve around the sun from east to west, there are 8 planets in our solar system, the biggest planet is Jupiter whereas Mercury is the smallest planet.

As defined by the International Astronomical Union in 2006, a planet is a celestial body that:

1. Orbits a star,
2. Has a surface area of at least 3,000 km²,
3. Receives its energy and light from the star it orbits,
4. Possesses enough mass for its gravity to overcome rigid body forces, resulting in a nearly round, hydrostatic equilibrium shape,
5. Has cleared its orbital path of other debris.

Types of Planets

1. Terrestrial or Inner Planet – They are found inside asteroid belts. Mercury, Venus, Earth, and Mars are called Terrestrial Planets or Inner Planets are primarily composed of rock and metal or their structure being similar to the Earth.
2. Gas Giants or Outer Planets – There are four of them: Jupiter, Saturn, Uranus, and Neptune. These planets are also referred to as Jovian Planets or Outer Planets due to their structural similarity to Jupiter.