Physical Geography

Until it lost its planetary status in 2006, Pluto was the coldest with an estimated surface temperature between -235 and -210 degrees Celsius. But Pluto has now been relegated the status of a Dwarf Planet.

If the star is about the mass of the Sun or less than that, it will turn into White Dwarfs. If the star is bigger than the Sun but not more than twice as big, it will turninto a Neutron Star or Pulsar. If the star is many times bigger than the Sun, it will turn into what is called a Black Hole.

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In 2126 it will be a bright naked-eye comet reaching about apparent magnitude 0.7.

The sky appears blue because the sunlight is scattered by the gas molecules in the atmosphere - a phenomenon known as Rayleigh scattering - named after the discoverer - a British physicist who also discovered Argon - Lord Rayleigh (1842-1919). So, if there was no atmosphere, the sky would appear black.

The planet Mercury is often cited as the most difficult of the five brightest naked-eye planets to see. Because it's the planet closest to the Sun, it never strays too far from the Sun's vicinity in our sky.

The correct sequence of planets in the descending order of their equatorial diameter is Uranus, Earth, Mars, Mercury.

The Foucault pendulum is a simple device named after French physicist Léon Foucault and conceived as an experiment to demonstrate the Earth's rotation.

Our solar system is so big it is almost impossible to imagine its size if you use ordinary units like feet or miles. The distance from Earth to the Sun is 93 million miles (149 million kilometers), but the distance to the farthest planet Neptune is nearly 3 billion miles (4.5 billion kilometers).

The correct sequence in decreasing order of their brightness is Venus, Sirius and Mars.

Pluto is considered as a dwarf planet. This is called so because it has not cleared its neighbourhood around its orbit. International Astronomic Unit declared it a Dwarf Panet in 2006. It orbits in a disc-like zone beyond the orbit of Neptune called the Kuiper belt, a distant region populated with frozen bodies left over from the solar system's formation.

Earth is the third inner planet and the one we know best. Of the four terrestrial planets, Earth is the largest, and the only one that currently has liquid water, which is necessary for life as we know it.

Kepler through his 'planetary law of motion' proved that every planet has an elongated path. Kepler had believed in the Copernican model of the solar system, which called for circular orbits, but he could not reconcile Brahe's highly precise observations with a circular fit to Mars' orbit – Mars coincidentally having the highest eccentricity of all planets except Mercury.

As compared to the orbit of the other given planets, Mars has nearest orbit to Sun. In the so-called perihelic opposition Mars is closest to the Sun and is particularly close to Earth: Oppositions range from about 0.68 AU when Mars is near aphelion to only about 0.37 AU when Mars is near perihelion.