World Asteroid Day 2019: When and why is it observed?

New Delhi, June 30: Today, the world is observing International Asteroid Day World Asteroid Day, June 30, acknowledges the dangers asteroids pose to the survival of life forms on our planet.

However, this year's Asteroid Day has a specific theme - discovering more asteroids.

So far, over 16,000 near Earth asteroids have been discovered according to NASA's Centre for NEO Studies.

Why is Asteroid Day observed on June 30?

The United Nations gave the call to declare the day as International Asteroid Day in December 2016, to "observe each year at the international level the anniversary of the Tunguska impact over Siberia, Russian Federation, on 30 June 1908, and to raise public awareness about the asteroid impact hazard."

What happened on 30 June 1908?

On 30 June, 1908, a flaming rock entered Tunguska (a part of the then Russian empire) in Siberia and exploded 5-10 km above the ground. The explosion, with the energy of 10-15 megatons of TNT, knocked or burned down 80 million trees within a radius of 30 kilometres. At that time, Siberia was wilderness, and had a very sparse population. Hence, no human casualties occurred. According to one estimate, the total weight of that meteorite was 40,000 tons.

The scale of the event was so huge that since 2014, Asteroid Day has been observed on the date of the Tunguska event.

What are Asteroids?

Asteroids are small rocky body that orbits around the sun. Mostly, they are found between the orbits of mars and Jupiter but some have more eccentric orbits. They are so small that are not considered as planets but they orbit Sun. They are known as the left over material of the Solar System. Our solar system began about 4.6 billion years ago when a big cloud of gas and dust collapsed. When this happened, most of the material fell to the center of the cloud and formed the sun.

The first asteroid was Ceres, discovered by Giuseppe Piazzi in 1801. Astronomer William Herschel first coined the word asteroid, which means "star-like" in 1802.