Solar System Notes of Geography Section for CDSE

Notes Solar System

A planet is any body in orbit around the Sun that a) has enough mass to form itself into a spherical shape and b) has cleared its immediate neighborhood of all smaller objects. A dwarf planet is not required to clear its neighborhood of other celestial bodies. The three dwarf planets are Pluto, Ceres, and Eris

Johannes Kepler’s laws of planetary motion.

First law The orbits of the planets in our solar system are elliptical, not circular 

Second Law A line joining a planet and the sun sweeps out equal areas during equal intervals of time as the planet travels along its orbit. This means that the planet travels faster while close to the sun and slows down when it is farther from the sun.

Third Law Establishes a universal relationship between the orbital properties of all the planets orbiting the sun. For the planets, the cubes of their distances from the sun are proportional to the squares of their orbital periods.

Isaac Newton showed that the bodies revolve about their common center of mass. Where one body is much more massive than the other, it is a convenient approximation to take the center of mass as coinciding with the center of the more massive body. e.g. Sun in Solar system.

Solar noon is the time or point in the sun's path at which the sun is on the local meridian. Obviously all the places on a meridian will experience solar noon simultaneously.

At the equator, the sun is directly overhead at twice a year during the equinoxes; March 21 (Vernal Equinox), and September 23 (Autumnal Equinox). During the equinoxes,the circle of passes through the poles to give equal lengths of day and night worldwide.

Perihelion is the nearest point in the earth’s or any other planet orbit to the Sun.  Earth reaches its perihelion on January 3 approximately.

Aphelion is the farthest point from the Sun and the Earth reaches it on July 4

Anything traveling at the escape velocity, or faster, can escape into space. Gravity pulls back anything traveling more slowly. Earth's escape velocity is 11 kilometers/second. With less surface gravity, the Moon's escape velocity is 2.4 kilometers/second. Hence it is much easier to escape into space from the Moon than from Earth.

 Pictures for Better Understanding 

Pictures taken from Internet for Illustrative Purpose