Why is Pluto a "Dwarf Planet" & other Celestial trivia

The week gone by saw the world celebrate the 25^th birthday of the internet on 23^rd August. On this day in 1991, the public gained access for the first time to the World Wide Web, which had been designed & deployed by computer scientist Tim Berners-Lee at CERN in Switzerland.

But today’s GK Nugget is about something else. On 24^th Aug 2006 the International Astronomical Union clarified the definition of a “planet”. It said that a celestial body must meet the following criteria in order to qualify as a planet:

1) It must be round.

2) It must orbit the sun.

3) It must have “cleared the neighbourhood" of its orbit. This means that as a planet travels, its gravity sweeps and clears the space around it of other objects.

Unfortunately, Pluto (which was discovered on Feb 18^th, 1930) doesn’t meet criteria #3 & therefore it was classified as a Dwarf Planet. For the common man, this was a shock, but amongst the circle of astronomers it wasn’t so surprising since Pluto’s status had been in question for almost 30 years.

And so kids now, no longer remember the names of the 9 planets by singing “My Very Educated Mother Just Showed Us Nine Planets”.

Here are some other interesting facts about the celestial bodies that revolve and rotate around the Sun.

Along with Pluto, there are 4 other Dwarf Planets in our solar system -  Ceres, Eris, Haumea, & Makemake.

Pluto is about the size of the moon. Nearly 170 Plutos could fit in the Earth.

It takes approximately 248 Earth years for Pluto to make 1 trip around the sun. Since astronomers discovered Pluto in 1930, it has not completed 1 trip around the sun. It still has more than 150 Earth years to go!

Pluto is so far away that it takes more than 5 Earth hours for light from the sun to reach it. The sun's light reaches Earth in only 8 Earth minutes!

Venus is the hottest planet. Even though Mercury is closest to the sun, it has no atmosphere which holds in the heat. Venus, on the other hand, has a very thick atmosphere which traps in the heat of the Sun.

Jupiter, the largest planet in the solar system, acts as a protective gate keeper for Earth, since its strong gravitational force pulls dangerous space debris into its orbit before it gets to us.

There are less than 2 days in a year on Mercury. That’s because it takes the planet 88 Earth days to go around the Sun, but Mercury takes 58 Earth days to rotate on its axis, i.e. to complete 1 Mercury day.

Seasons on Uranus last for almost 20 Earth years. This is because the planet has an orbital tilt of 82 degrees (compared to Earth’s 23.4 degrees). Uranus thus is almost on its side which causes such odd weather.

The Sun, which is 149.6 million kms away from us, is so huge that it makes up 99% of the mass of the solar system. All the planets, asteroids, etc make up just 1% of the mass.