SOLAR SYSTEM

SOLAR SYSTEM

• The sun, the eight planets and their satellites (or moons), and thousands of other heavenly bodies such as asteroids, comets, meteors and dwarf plants form Solar system.
• Our planet Earth is also a part of the solar system.
• The solar system is located in the Milky Way galaxy. The Sun is located at the centre of the solar system while other heavenly bodies of solar system revolve around it due to the gravitational pull.
• The sun is the only source of energy in solar system.
• the Sun is an star of average size and the planets are Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune. Some planets have natural satellites revolving around them called moon. Also there are numerous comets, asteroids, and meteoroids; and the interplanetary medium.

THE SUN

• It is the star of the solar system.
• It is almost 13 lakh times huge than the Earth.
• In diameter it is about 14 lakh kilometers.
• It contains 71% Hydrogen, 26.5% Helium and 2.5% other elements..
• The surface temperature of sun is almost 1.571×107 K or 15,000,000^o
• solar winds which generate on the sun are streams of charged particles. When magnetic field of the sun travels through the space, it generates.
• It has a very strong magnetic field of sun.
• Magnetic field of the sun is responsible for solar flares during magnetic storm which can be seen as sun spot.
• sunlight reaches to the surface of the Earth in 8 min and 16.6 sec.
• There are different layers in the sun. from the centre they are :The core (the interior part), Radiative zone, Convective zone; Photosphere (visible surface); Chromosphere; and Corona (outermost layer visible during eclipses).

PLANETS

• A Planet is a celestial body which orbits a star or stellar remnant due to that’s gravity. They do not emit light like star and the sun.
• There are eight planets in the Solar System. The sequence of planets according to their distance from the Sun is Mercury, Venus, Earth, mars, Jupiter, Saturn, Uranus, and Neptune.

• The eight planets have been divided into two groups due to some common features.

1. ‘Terrestrial planets’/‘Rocky planets’ theses are Mercury, Venus, Earth and Mars
2. ‘Jovian planets’/‘Gaseous planets’ These are Jupiter, Saturn, Uranus and Neptune)

MERCURY

• smallest planet in the Solar System.
• Nearest to the Sun
• Revolution period 87.97 days, the shortest in the Solar System.
• It is extremely hot planet.
• No chance of life due to absence of gases like CO₂, N₂, H₂ and O.
• Radiations reach direct because of the absence of Ozone like layer.

VENUS

• This planet is nearest to the Earth.
• It is the brightest planet in solar system.
• It orbits in the opposite direction i.e. East to West.
• Its revolutionary period to the Sun is 224.7 Earth days.
• It is known as the ‘Evening Star’ and the‘Morning Star’.
• It is called ‘Veiled Planet’ because it is surrounded by a thick cloud cover.
• It is the hottest planet of our Solar System.
• It is also known as the ‘Earth’s twin’ because it is much like the Earth in size and mass.

 EARTH

• It is the only astronomical object which harbors life.
• Earth formed over 4.5 billion years ago.
• Its axis is tilted at 23_1/2 degree and makes 66_1/2 degree angle.
• Its revolutionary period to the Sun in 365.26 days.
• It is known as the ‘Watery Planet’ or the ‘Blue Planet’ due to the presence of huge amount of water on it.
• It has a large quantity of oxygen than other planet of solar system.
• It has one natural satellite or Moon.
• earth revolve around the earth in an oval path that’s why in a year it is two times closest to the sun called perihelion. And two time farthest from the sun called aphelion. The speed of a body in the solar system is greatest at the perihelion and least at the aphelion.
• As Earth around the Sun, the moon also revolve around the Earth in an oval path and experiences two times least distance and two times maximum distance from the Earth. Moon’s furthest point from the earth is called apogee its closest point to the earth is called perigee.

Moon

• It revolve around the Earth in an oval orbit
• Its Average distance from the earth is 3, 84,365 km
• Its Maximum distance from the earth during Apogee is 4, 06,000 km
• Minimum distance from the earth during Perigee is 3,64,000 km
• Its revolutionary period to Earth is 27 days 7 hours 43 min 11.47 sec
• Its Rotational time on its axis is 27 days 7 hours 43 min 11.47 sec
• It has no Atmosphere
• Its Diameter is about 3,476 km
• Its Mass compared to the earth is 1:81.30
• Its Density relative to that of water is 3.34
• Its Density relative to that of the earth is 0.6058
• Highest point on the Moon is Mt Leibnitz (35,000 ft.). it is situated on the South Pole of the moon.

MARS

• It is the second-smallest planet in the Solar System after Mercury.
• Its revolutionary period to the sun is 687 (Earth) days.
• It has two natural satellites named Phobes and Demos.

JUPITER

• It is the fifth planet from the Sun and the largest in the Solar System.
• It is a gas giant. its mass is equals to one-thousandth that of the Sun, but two-and-a-half times that of all the other planets in the Solar System combined.
• It is the biggest planet of the solar system.
• hydrogen and helium are two major gases of Jupiter.
• It has very high gravitational force.
• It is the fastest rotating planet with a rotational velocity of 12.6 km/s.
• It has a great red spot which is anticyclone storms with a diameter of 24,000 km. These storms were first identified in 1665 by Giovanni Cassini.
• The planet has 3 main segments,

1. an inner torus of particles known as the halo,
2. a relatively bright main ring, and an outer gossamer ring.

• The planet has four major moons known as Galilean Moons, e. Io, Europa, Ganymede, and Callisto.
• NASA had sent a mission named Pioneer 10 spacecraft in 1973 which was the first to visit Jupiter.

SATURN

• It is the least dense planet.
• It has rings around it. Galileo was the first person to observe them in 1610.
• Pioneer 11 was the first to observe the Saturn from 20,000 km.
• It has nearly 62 moons.
• Saturn’s rotation period is 10 hours and 14 minutes.
• It has a tilted axis just like Earth.
• ice geysers blasting out of Enceladus’ southern pole are recently discovered by NASA’s Cassini spacecraft.

URANUS

• Sir William Herschel discovered the planet in 1781
• The name ‘Uranus’ was termed by Johann Bode.
• The rotational period for the planet is 17 hours and 14 minutes.
• Revolution period is 84 Earth days.
• It is the coldest planet with minimum recorded temperature of -224°C.
• In 1986, the Voyager 2 spacecraft swept past the planet at a distance of 81,500 km.

NEPTUNE

• Its revolutionary period is 164.8 Earth days.
• Its rotational period is only 18 hours.
• It was discovered in the year 1846 by Jean Joseph Le Verrier. Since then, its first revolution was completed in the year 2011.
• It has second high gravitaty after Jupiter.
• Like Saturn it also has ring system.

PLUTO

• Earlier 2006, Pluto was a planet. Now it is reclassified to the category of a dwarf planet.
• It was discovered on February 18th, 1930 by the Lowell Observatory.
• It has five known moons.

Pluto’s demotion from a planet to dwarf planet

• After the discovery of Pluto a large numbers of other celestial bodies were discovered which were similar to Pluto. It was not possible to classify all these celestial bodies as planet. That’s why The International Astronomical Union (IAU) in 2006, decided to change the definition of planet and form a new category of celestial bodies revolving around the sun that is dwarf planet. The International Astronomical Union (IAU) has given three criteria for a full-sized planet such as:

1. It is in orbit around the Sun.
2. It has sufficient mass to assume hydrostatic equilibrium (a nearly round shape).
3. It has “cleared the neighborhood” around its orbit.

• So any large body that does not meet these criteria is now classed as a “dwarf planet,” and that includes Pluto, which shares its orbital neighborhood with Kuiper belt objects.

NATURAL SATELLITES OF PLANETS

• A natural satellite is a celestial body that orbits a planet or a body revolving around the sun.
• In the Solar System there are six planetary satellite systems containing 205 known natural satellites.