All About Solar System

Dear Readers,

As all of you know that "Solar System" is an important and huge part of this Universe, we should be aware of it on a high note. So, we are providing the brief notes on the topic. Just go through them properly as this can help for upcoming SSC CHSL and other exams.

The Solar System:

The solar system is made up of the sun and everything that orbits around it, including planets, moons, asteroids, comets and meteoroids. It extends from the sun, called Sol by the ancient Romans, and goes past the four inner planets, through the Asteroid Belt to the four gas giants and on to the disk-shaped Kuiper Belt and far beyond to the giant, spherical Oort Cloud and the teardrop-shaped heliopause. Scientists estimate that the edge of the solar system is about 9 billion miles (15 billion kilometers) from the sun.

Discovery:

For Millennia, astronomers have followed points of light that seemed to move among the stars. The ancient Greeks named these planets, meaning "wanderers." Mercury, Venus, Mars, Jupiter and Saturn were known in antiquity, and the invention of the telescope added the Asteroid Belt, Uranus, Neptune, Pluto and many of these worlds' moons. The dawn of the space age saw dozens of probes launched to explore our system, an adventure that continues today. The discovery of Eris kicked off a rash of new discoveries of dwarf planets. 

Formation :

Many scientists think our solar system formed from a giant, rotating cloud of gas and dust known as the solar nebula. As the nebula collapsed because of its gravity, it spun faster and flattened into a disk. Most of the material was pulled toward the center to form the sun. Other particles within the disk collided and stuck together to form asteroid-sized objects named as planetesimals, some of which combined to become the asteroids, comets, moons and planets.

The solar wind from the sun was so powerful that it swept away most of the lighter elements, such as hydrogen and helium, from the innermost planets, leaving behind mostly small, rocky worlds. The solar wind was much weaker in the outer regions, however, resulting in gas giants made up mostly of hydrogen and helium.

The sun :

The sun is by far the largest object in our solar system, containing 99.8 percent of the solar system's mass. It sheds most of the heat and light that makes life possible on Earth and possibly elsewhere. Planets orbit the sun in oval-shaped paths called ellipses, with the sun slightly off-center of each ellipse.

The Planets :

There are eight planets in our Solar System. Starting with the closest to the sun they are Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune. The closest four planets (Mercury, Venus, Earth, and Mars) are termed terrestrial planets, meaning they have a hard rocky surface. The furthest four planets (Jupiter, Saturn, Uranus, and Neptune) are called gas giants. These planets are much larger and their surface is composed of gas elements (mostly hydrogen).

Inner solar system:

The four inner four planets — Mercury, Venus, Earth and Mars — are made up mostly of iron and rock. They are known as terrestrial or earth like planets because of their similar size and composition. Earth has one natural satellite — the moon— and Mars has two moons — Deimos and Phobos.

Between Mars and Jupiter lies the Asteroid Belt. Asteroids are minor planets, and scientists estimate there are more than 750,000 of them with diameters larger than three-fifths of a mile (1 km) and millions of smaller asteroids. The dwarf planet Ceres, about 590 miles (950 km) in diameter, resides here. A number of asteroids have orbits that take them closer into the solar system that sometimes lead them to collide with Earth or the other inner planets.

Outer solar system :

The four outer planets — Jupiter, Saturn, Uranus and Neptune — are giant worlds with thick outer layers of gas. Nearly all their mass is made up of hydrogen and helium, giving them compositions like that of the sun. Beneath these outer layers, they have no solid surfaces — the pressure from their thick atmospheres liquefy their insides, although they might have rocky cores. Rings of dust, rock, and ice encircle all these giants, with Saturn's being the most famous.

Other Objects :

In addition to the Sun and the eight planets, there are other objects that are part of the Solar System.

Dwarf planets - Dwarf planets are objects similar to planets in the Solar System, however they are defined as not large enough to have "cleared their orbital region of other objects." Some of the dwarf planets in the Solar System include Pluto, Ceres, Eris, Haumea, and Makemake.

Comets - Comets are often known as dirty snowballs, and consist mainly of ice and rock. When a comet's orbit takes it close to the sun, some of the ice in its central nucleus turns into gas that shoots out of the comet's sunlit side, which the solar wind carries outward to form into a long tail. Short-period comets that complete their orbits in less than 200 years are thought to originate from the disk-shaped Kuiper Belt, while long-period comets that take more than 200 years to return are thought to come from the spherical Oort Cloud.

Asteroid belt - The asteroid belt is a region between the planets Mars and Jupiter. In this region thousands of rocky objects orbit the Sun. They range in size from tiny dust like particles to the dwarf planet Ceres.

Kuiper belt - The Kuiper belt is a region of thousands of small bodies that exists outside the orbit of the planets. Objects in the Kuiper belt consist of "ices" such as ammonia, water, and methane.

Oort cloud - The Oort cloud exists much further out than the Kuiper belt. Around a thousand times as far away from the Sun. Up to now scientists have only guessed at the existence of the Oort cloud which they think consists of thousands of small icy objects. The Oort cloud is at the very edge of the Solar System.

Milky Way :

The Solar System is part of a bigger grouping of stars called a galaxy. Our galaxy is the Milky Way. The Solar System orbits around the center of the Milky Way. 

Interesting Facts about the Solar System :

Uranus and Neptune contain many "ices" such as water, methane, and ammonia they are often referred to as the "ice giants."

Scientists estimate there are around 200 billion stars in the Milky Way galaxy.Pluto was once considered a full planet, but was redefined as a dwarf planet in 2006.About 99.85% of the mass of the Solar System is the Sun. All the other planets, asteroids, moon, etc. together make up less than 0.15% of the Solar System's mass.The area around the Sun where the Sun's solar wind has an influence is called the heliosphere.All of the planets orbit the Sun in the same counterclockwise direction. Scientists who study the solar system and outer space are called astronomers.

SOLAR SYSTEM :

• The Sun is at the centre of the solar system.

• Hydrogen and Helium are the main gases present in the Sun.

• It has a surface temperature of about 6000°C.

• Light (at the speed of 300,000 km per second) takes about 8.5 minutes to reach the Earth from the sun.

• There are eight planets in the Solar system.

• A ninth planet has been recently discovered by NASA named as Carla.

• The sequence of planets according to their distance from the Sun is Mercury, Venus, Earth, Mars, Jupiter, Saturn,Uranus, Neptune. The sequence of planets according to their size (in discending order i.e., from big to small) is Jupiter,Saturn, Uranus, Neptune , Earth, Venus, Mars, Mercury.

FACTS ABOUT PLANETS :

• Mercury is the closest planet to the Sun.

• Venus is like the Earth in size and mass and hence also known as the “Earth’s twin”.

• The Earth is 23½° tilted on its axis and thus makes 66½º angle with the plane of its orbit

• It takes 365 days and 5 hours 45 minutes to revolve around the Sun.

• Earth is known as the “watery planet” or the “blue planet” due to presence of a huge amount of water.

• The earth has a protective blanket of ozone layer high up in its atmosphere to save life from harmful ultraviolet radiations coming from the sun.

Facts About our Planet — the Earth

•  Estimated age of the Earth : 4600 million years.
•  Mean distance from the Sun : 149,407,000 kms.
•  Equatorial diameter : 12753 kms.
•  Polar diameter : 12710 kms
•  Equatorial circumference : 40,066 kms.
•  Period of rotation : 23 hrs. 56 mts. 4.09 sec. (24 hrs.)
•  Period of revolution : 365 days 5 hours 48 mts and 45.51 seconds. (365¼ days)
•  Total area : 510,100,500 sq. kms.

The Moon :

• The Moon is the only satellite of the earth.
• It takes 27 days, 7 hours and 43 minutes to rotate on its axis(this period of about 27½ days is called the sideral month)and approximately the same period of time it takes to revolve around the earth. The moon’s period of revolution with reference to the sun is about 29.53 days (29 days, 12 hours,44 mintues and 2.8 seconds). This period is called a synodic month.
• The light from the moon takes 1.3 seconds to reach the earth.
•  The size of the Moon is one-fourth (1/4 th) the size of the Earth.
•  Gravitational pull of Moon is one-sixth (1/6 th) that of the Earth.
•  Jupiter is the largest planet of the solar system.
•  Saturn has bright concentric rings which are made up of ice and ice-covered dust particles which revolve around it.
•  Neptune is very similar to Uranus and can be considered its twin. Neptune is surrounded by methane rings at sub zero temperature.